JP6317839B2 - Color conversion table creation device and method, and program - Google Patents

Description

  The present invention relates to an apparatus and method for creating a color conversion table, and a program, and more particularly to a color conversion technique for image data applied to color reproduction by a printing apparatus.

  In the field of printing, color conversion processing of image data is performed using a color conversion table such as an ICC (International Color Consortium) profile in order to perform target color reproduction by a printing apparatus. The ICC profile is usually created based on the color measurement result of the color chart printed out for each printing apparatus.

  Patent Document 1 discloses an image processing apparatus that can match the color tones of two printed materials without using a color chart. According to Patent Document 1, each of a reference printed matter output by a first image output device as a reference printer and a user printed matter output by a second image output device as a user printer is read by a scanner. A color tone conversion parameter is obtained from the correspondence between the color component values, and the color tone equivalent to the color tone of the reference printed matter is reproduced by correcting the output image of the second image output device with the obtained color tone conversion parameter.

JP2013-30996A

  In order to realize a color management system (CMS) using an ICC profile, an input profile representing a color reproduction target and an output profile representing a color reproduction of a printing apparatus are required. The input profile is also called a target profile, and the output profile is also called a printer profile.

  However, in actual printing operations, only the original image data and the color sample printed matter are provided from the client as the client, and it is sometimes required to match the color of the printed matter with the color of the color sample printed matter. The color sample printed matter may be unclear as to what printing conditions were used for printing. That is, the target profile necessary for printing the document image data is unknown, and the actual color sample printed matter provided from the client is the target of color reproduction. In such a case, it is necessary for a plate making and printing operator to manually correct image data and adjust printing conditions, and to perform color matching by trial and error, which is very troublesome.

  In the case of the technique described in Patent Document 1, in addition to reading the reference printed matter printed by the reference printer with the scanner, the user printer is printed with the user printer, and the image of the printing result is read with the scanner to obtain the user image data. Therefore, it takes time for color adjustment work.

  Further, the technique described in Patent Document 1 obtains a color tone parameter for each R / G / B color component read by a scanner, and uses the color tone conversion parameter for each color component for each R / G / B color component. Color correction is performed by one-dimensional conversion. Such a conventional method is considered to be sufficient for correcting a color tone difference of about an individual difference between printer devices, but a reference printer (first image output device) that outputs a reference print product and a first printer as a user printer. When the printing characteristics of the second image output device are greatly different, the degree of freedom of color correction is not sufficient, and the color correction accuracy may be lowered.

  Furthermore, as described in FIG. 4 of Patent Document 1, the color tone conversion parameter in the technique described in Patent Document 1 includes a first image output device (printer 1), a scanner, and a second image output device ( This is based on the relationship obtained by sequentially converting the correspondence of the color components in each device of the printer 2). In other words, the color tone conversion parameter described in Patent Document 1 is not a color profile, and is based on an original conversion (FIG. 4 of Patent Document 1), and thus has no versatility.

  The present invention has been made in view of such circumstances, solves at least one of the plurality of problems described above, can simplify the adjustment work of color matching of a printed matter with respect to a target printed matter as a color reproduction target, It is an object of the present invention to provide a color conversion table creation apparatus and method, and a program capable of improving the reproduction accuracy.

  In order to achieve the above object, the following invention mode is provided.

  The color conversion table creating apparatus according to the first aspect includes an image reading unit that reads a target print and obtains read image data representing a read image of the target print, and a signal value of the first color space obtained from the image reading unit. The signal value of the first color space is converted to the chromaticity value of the second color space using the first color conversion table representing the correspondence relationship with the chromaticity value of the second color space which is a device-independent color space. By the first color conversion unit for converting the image data into the image data, the processing for associating the positional relationship between the read image data represented by the signal values of the first color space and the original image data of the target printed matter, or by the first color conversion unit An image association unit that performs processing for associating the positional relationship between the read chromaticity value image data obtained by converting the signal value of the read image data into the chromaticity value of the second color space and the original image data of the target printed matter; The third color space is a device-dependent color space. A third color space of the document image data based on the correspondence between the document image data represented by the value and the chromaticity value of the read image obtained through the processing by the image association unit and the first color conversion unit. A color conversion table creation unit that creates a second color conversion table representing a multidimensional correspondence with the second color space.

  The read color data obtained from the image reading unit may be configured to perform color conversion processing by the first color conversion unit after performing image correlation processing by the image correlation unit, or the first color conversion The image association processing may be performed by the image association unit after the color conversion processing by the unit is performed.

  The term “chromaticity value” is not limited to the XYZ color system, but means a color value represented by the color coordinates of the device-independent color space.

  The second color conversion table created in the first mode can be used as a color conversion table for the target profile. According to the first aspect, it is possible to create a color conversion table (second color conversion table) of the target profile by omitting the output of the printed matter by the printing apparatus and the reading operation of the printed matter.

  The second color conversion table created in the first mode is a multidimensional correspondence between the color space (third color space) of document image data and the device-independent color space (second color space). Therefore, compared with the conventional configuration in which color correction is performed in a one-dimensional correspondence relationship for each color component, the degree of freedom of color correction is high, and highly accurate color matching is possible.

  Furthermore, according to the first aspect, color management using an ICC profile is possible, and a versatile technique can be provided.

  As a second aspect, in the color conversion table creating apparatus according to the first aspect, the color measurement target is measured by performing color measurement using at least one of the target print and the color sample different from the target print as a color measurement target. A colorimetric unit that acquires colorimetric values, a colorimetric target document image signal acquisition unit that acquires a document image signal corresponding to a position on the document image data from which the colorimetric values are acquired by the colorimetric unit, and a colorimetric unit A color measurement target image signal acquisition unit including at least one of the color measurement target read image signal acquisition units that acquire a read image signal corresponding to a position on the read image data from which the color measurement value has been acquired. be able to.

  It is desirable to use a spectrocolorimeter as the color measurement unit. According to the 2nd aspect, the error of the chromaticity value grasped | ascertained from the reading image by the image reading part can be reduced, and the precision of color matching can further be improved.

  As a third aspect, in the color conversion table creation device according to the second aspect, the color conversion result by the first color conversion unit corresponds to the position of the original image data from which the colorimetric value is obtained by the colorimetry unit. A chromaticity value replacement unit that replaces the chromaticity value to be replaced with the colorimetric value acquired by the colorimetry unit may be provided.

  As a fourth aspect, in the color conversion table creation device according to the second aspect or the third aspect, a first color conversion table database in which a plurality of color conversion tables applicable as the first color conversion table are stored; A first color conversion table selection unit that selects one color conversion table from among a plurality of color conversion tables stored in the first color conversion table database. Including a color conversion table representing a correspondence relationship between the read signal of the image reading unit and the chromaticity value for each combination of the color material type and the base material type used for creating the printed matter according to the first color conversion table selection unit, One of a plurality of color conversion tables is selected based on the correspondence between the read image signal corresponding to the position on the read image data from which the color measurement value has been acquired by the color measurement unit and the color measurement value acquired by the color measurement unit. One It may be configured to select a color conversion table.

  For example, the first color conversion table selection unit selects the chromaticity value of the read image signal obtained by referring to the color conversion table stored in the first color conversion table database and the measurement value obtained from the color measurement unit. The color difference with the color value is calculated, and the color conversion table in which the average value of color differences (referred to as “average color difference”) or the maximum value of color differences (referred to as “maximum color difference”) is minimized is stored in the first color conversion table database. It can be set as the structure selected from inside.

  According to the fourth aspect, it is possible to further increase the accuracy of the chromaticity value obtained from the image read by the image reading unit.

  As a fifth aspect, in the color conversion table creation device according to any one of the second aspect to the fourth aspect, a read image signal corresponding to a position on the read image data from which the colorimetric value is acquired by the colorimetric unit; The first color conversion table correction unit that corrects the first color conversion table based on the correspondence relationship with the color measurement values acquired by the color measurement unit may be provided.

  According to the fifth aspect, the chromaticity value acquired via the image reading unit can be brought close to the colorimetric value obtained from the colorimetric unit, and the accuracy of the chromaticity value can be increased.

  As a sixth aspect, in the color conversion table creation device according to any one of the first to fifth aspects, the image association unit extracts a partial image corresponding to the document image data from the read image data It can be set as the structure which has the image extraction part which performs.

  According to the sixth aspect, even when the original image data and the image content of the printing surface of the target printed material do not correspond one-to-one, the target color matching can be performed.

  As a seventh aspect, in the color conversion table creation device according to any one of the first aspect to the sixth aspect, the color conversion table creation unit includes a second color conversion table corresponding to the signal value of the document image data. A configuration may be adopted in which processing for setting the chromaticity value of the second color space associated with the signal value of the document image data at one or a plurality of grid points is performed.

  When the signal value of the document image data directly corresponds to the value of the lattice point, the chromaticity value can be set to one lattice point corresponding directly. Further, it is preferable to set the same chromaticity value for adjacent grid points around one grid point that directly corresponds.

  On the other hand, if there is no grid point that directly corresponds to the signal value of the document image data, a plurality of grid points that surround the signal value (document image signal value) of the document image data are expressed as “second corresponding to the signal value of document image data”. And a plurality of grid points in the color conversion table ”, and chromaticity values can be set for the plurality of grid points.

  As an eighth aspect, in the color conversion table creation device according to the seventh aspect, the color conversion table creation unit uses the existing color conversion table as a temporary color conversion table, and the original image data with respect to the temporary color conversion table. The processing for setting the chromaticity value of the second color space associated with the signal value of the document image data to one or a plurality of grid points corresponding to the signal value of.

  As a ninth aspect, in the color conversion table creating device according to any one of the first to sixth aspects, the color conversion table creating unit predicts a color reproduced by a color material used for printing. The reproduction model may be used to perform a process of calculating chromaticity values of one or more grid points of the second color conversion table corresponding to the signal value of the document image data.

  As a tenth aspect, in the color conversion table creation device according to any one of the first aspect to the ninth aspect, the image association unit is configured to store the original image data and the read image data subjected to the process of associating the positional relationship. From each, it can be set as the structure which performs the color extraction process which extracts the corresponding color information.

  As an eleventh aspect, in the color conversion table creating apparatus according to the tenth aspect, the color extraction processing includes processing for setting a region of interest in document image data and processing for determining whether the region of interest satisfies the first extraction condition. And extracting the signal value of the document image data as color information from the region of interest that satisfies the first extraction condition, and satisfying the first extraction condition in the read image data that has been subjected to the process of associating the positional relationship. A corresponding color information extraction process for extracting a signal value of read image data as color information from a region at a position corresponding to the region of interest.

  As a twelfth aspect, in the color conversion table creation device of the eleventh aspect, the first extraction condition is that the color difference within the region of interest is equal to or less than a first extraction threshold value defined as an allowable range. It can be set as the structure containing these conditions.

  As a thirteenth aspect, in the color conversion table creation device according to the eleventh aspect or the twelfth aspect, the color extraction process includes a process of determining whether or not the region of interest satisfies the second extraction condition, and extracts corresponding color information As processing, processing was performed for extracting the signal value of the document image data as color information from the region of interest satisfying the first extraction condition and satisfying the second extraction condition, and associating the positional relationship with each other. A configuration including a process of extracting a signal value of read image data as color information from a region at a position corresponding to a target region that satisfies the first extraction condition and the second extraction condition in the read image data can be employed.

  As a fourteenth aspect, in the color conversion table creating apparatus according to the thirteenth aspect, the second extraction condition is that the read image data exists in a region corresponding to the region of interest that satisfies the first extraction condition, and A configuration including a condition that an image defect does not exist in the region of the read image data at a position corresponding to the region of interest that satisfies the first extraction condition can be employed.

  Examples of the image defect include scratches on the target printed matter and dust attached when the target printed matter is read.

  As a fifteenth aspect, in the color conversion table creation device according to any one of the eleventh aspect to the fourteenth aspect, the color extraction process includes a process of determining whether the region of interest satisfies the third extraction condition, As the correspondence color information extraction processing, the signal value of the document image data as color information is extracted from the region of interest that satisfies the first extraction condition and satisfies the third extraction condition, and associates the positional relationship with each other. A process of extracting a signal value of the read image data as color information from an area at a position corresponding to the target area that satisfies the first extraction condition in the read image data that has been processed is performed. As a third extraction condition, It can be set as the structure by which any one condition of being a non-surface process area | region without surface processing or being a surface process area | region with surface processing is defined.

  As a sixteenth aspect, in the color conversion table creation device according to any one of the first aspect to the ninth aspect, the image association unit performs document image data and read chromaticity value image data subjected to a process of associating a positional relationship. The color extraction processing for extracting the corresponding color information from each of these can be performed.

  As a seventeenth aspect, in the color conversion table creating apparatus according to the sixteenth aspect, the color extraction processing includes processing for setting a region of interest in document image data and processing for determining whether the region of interest satisfies the first extraction condition. The first extraction in the read chromaticity value image data in which the signal value of the document image data as color information is extracted from the region of interest that satisfies the first extraction condition and the positional relationship is associated. And a corresponding color information extraction process for extracting the chromaticity value of the read chromaticity value image data as the color information from the area corresponding to the target area that satisfies the condition.

  As an eighteenth aspect, in the color conversion table creating apparatus according to the seventeenth aspect, the first extraction condition is that a color difference within the region of interest is equal to or less than a first extraction threshold value defined as an allowable range. It can be set as the structure containing these conditions.

  As a nineteenth aspect, in the color conversion table creation device according to the seventeenth aspect or the eighteenth aspect, the color extraction process includes a process of determining whether or not the region of interest satisfies the second extraction condition. As processing, processing was performed for extracting the signal value of the document image data as color information from the region of interest satisfying the first extraction condition and satisfying the second extraction condition, and associating the positional relationship with each other. A configuration including processing for extracting the chromaticity value of the read chromaticity value image data as color information from a region at a position corresponding to the target region that satisfies the first extraction condition and the second extraction condition in the read chromaticity value image data It can be.

  As a twentieth aspect, in the color conversion table creation device according to the nineteenth aspect, the second extraction condition is that the read image data exists in a region corresponding to the region of interest that satisfies the first extraction condition, and A configuration including a condition that an image defect does not exist in the region of the read image data at a position corresponding to the region of interest that satisfies the first extraction condition can be employed.

  As a twenty-first aspect, in the color conversion table creation device according to any one of the seventeenth aspect to the twentieth aspect, the color extraction process includes a process of determining whether the region of interest satisfies the third extraction condition, As the correspondence color information extraction processing, the signal value of the document image data as color information is extracted from the region of interest that satisfies the first extraction condition and satisfies the third extraction condition, and associates the positional relationship with each other. Extracts the chromaticity value of the read chromaticity value image data as color information from the region corresponding to the region of interest that satisfies the first extraction condition and the third extraction condition in the read chromaticity value image data that has been processed. The processing is performed, and as the third extraction condition, either a non-surface processed region without surface processing or a surface processed region with surface processing is determined. This Can.

  A color conversion table creation method according to a twenty-second aspect includes an image reading step of reading a target printed matter to obtain read image data representing a read image of the target printed matter, and a signal value of the first color space obtained from the image reading step. The signal value of the first color space is converted to the chromaticity value of the second color space using the first color conversion table representing the correspondence relationship with the chromaticity value of the second color space which is a device-independent color space. By a first color conversion step for converting to a color image, a process for associating the positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter, or the first color conversion step An image association step for performing a process of associating the positional relationship between the read chromaticity value image data obtained by converting the signal value of the read image data into the chromaticity value of the second color space and the original image data of the target printed matter; The third device-dependent color space Based on the correspondence between the original image data represented by the signal value of the color space and the chromaticity value of the read image obtained through the processing in the image association step and the first color conversion step, the third of the original image data. A color conversion table creating step for creating a second color conversion table representing a multidimensional correspondence between the color space and the second color space.

  In the color conversion table creation method of the 22nd aspect, the same matters as the specific matters of the color conversion table creation device specified in the 2nd to 21st aspects can be appropriately combined. In that case, the processing unit and the functional unit as the means for performing the processing and function specified in the color conversion table creating apparatus can be grasped as the elements of the “process (step)” of the corresponding processing and operation.

  The program according to the twenty-third aspect has a function of acquiring read image data representing a read image of a target printed material from an image reading unit that reads the target printed material, a signal value of the first color space obtained from the image reading unit, and device independence. The signal value of the first color space is converted to the chromaticity value of the second color space using the first color conversion table representing the correspondence relationship with the chromaticity value of the second color space that is the color space. Processing for associating the positional relationship between the first color conversion function and the read image data represented by the signal value of the first color space and the original image data of the target printed matter, or the read image data by the first color conversion function An image association function for performing a process of associating the positional relationship between the read chromaticity value image data obtained by converting the signal value of the image data into the chromaticity value of the second color space and the original image data of the target printed matter, and device-dependent colors The third color space, which is the space The third color space of the document image data based on the correspondence between the document image data represented by the signal value and the chromaticity value of the read image obtained through the processing by the image association function and the first color conversion function. And a color conversion table creation function for creating a second color conversion table representing a multidimensional correspondence relationship between the first color space and the second color space.

  Regarding the program of the 23rd aspect, the same matters as the specific matters of the color conversion table creation device specified in the 2nd aspect to the 21st aspect can be appropriately combined. In this case, the processing unit or function unit as a means for performing the processing or function specified in the color conversion table creating apparatus can be grasped as an element of the “function” of the program that performs the corresponding processing or operation.

  According to the present invention, a color conversion table (second color conversion table) as a target profile can be created based on the document image data and the target printed matter. According to the present invention, when creating the color conversion table of the target profile, the output of the printed material by the printing apparatus and the reading operation of the printed material can be omitted, and the color matching operation can be simplified.

  Further, according to the present invention, the color conversion table (the second color space) representing the multidimensional correspondence relationship between the color space (third color space) of the document image data and the device-independent color space (second color space). Since the color conversion table is created, more accurate color matching is possible compared to the case where color adjustment is performed using a conventional one-dimensional correspondence.

  According to the present invention, even when the target profile is unknown, color management using the ICC profile is possible, and a versatile technique can be provided.

1 is a block diagram illustrating a system configuration of a printing system including a color conversion table creation device according to an embodiment of the present invention. 1 is a block diagram illustrating an overall outline of a printing system. 1 is a block diagram illustrating a first main configuration of a printing system. FIG. It is a block diagram which shows the modification of a 1st main structure. It is a block diagram which shows the 2nd main structure. It is the flowchart which showed the procedure of the process by the 2nd main structure. It is the block diagram which showed the specific example of the position alignment process of the image in an image matching part. FIG. 8A shows an example of document image data, and FIG. 8B shows an example of a target printed matter. It is a block diagram of the structure which performs the process of image matching including pre-processing. 5 is a chart showing an example of correspondence data between document image signals and chromaticity values. FIG. 6 is an explanatory diagram showing lattice points in a color space (here, a CM plane) of document image data corresponding to the input side of a color conversion table. It is explanatory drawing of the calculation method of chromaticity value by Neugebauer model. It is a principal part block diagram regarding the 2nd color conversion part. 6 is a chart showing an example of correspondence data of a document image signal, a target chromaticity value, a printing chromaticity value, and a differential chromaticity value. It is a conceptual diagram in the case of using a color correction table. It is a figure which shows the example of the graphical user interface (GUI; graphical user interface) at the time of selecting a colorimetric position in the structure which uses a spectrocolorimeter together. It is the block diagram which showed the structure which concerns on the 1st example of a colorimetric value utilization method. FIG. 6 is a block diagram illustrating a configuration in which a function of replacing a chromaticity value with a colorimetric value is added to the second main configuration illustrated in FIG. 5. It is a block diagram which shows the structural example provided with the means to perform selection and correction | amendment of a scanner profile based on a colorimetric value in the 1st main structure. It is a block diagram which shows the structural example provided with the means to perform selection and correction | amendment of a scanner profile based on a colorimetric value in the 2nd main structure. It is a block diagram which shows the modification of the structure shown in FIG. It is a block diagram which shows the modification of the structure shown in FIG. It is a flowchart which shows the example of the color extraction method. It is a conceptual diagram which shows the example of the process which sets an attention area to original image data. It is a figure which shows the example of the read image data obtained from an image reading part. FIG. 25 is a diagram showing an example of an area extracted from the document image data shown in FIG. 24 as satisfying a first extraction condition. FIG. 26 is a diagram illustrating an example of a region extracted from the read image data illustrated in FIG. 25 as satisfying a second extraction condition. It is explanatory drawing used in order to demonstrate the area | region around the attention area | region. It is a top view of the whole scanning surface used in order to demonstrate the area | region with low reliability in the scanner used for an image reading part. FIG. 11 is a chart in which an example of “weight” indicating the importance of color is added to the correspondence data illustrated in FIG. 10. FIG. 15 is a chart in which an example of “weight” indicating the importance of a color is added to the correspondence data illustrated in FIG. 14. It is explanatory drawing used in order to demonstrate how to obtain | require the gravity center of a white area | region. It is a schematic diagram which shows the example of the document image data for package printing. It is a flowchart of the color extraction process which added the presence or absence of surface processing to the conditions of color extraction. It is a block diagram which shows the system configuration | structure of the printing system which concerns on other embodiment of this invention. FIG. 36 is a block diagram showing a second main configuration in the printing system of FIG. 35.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings.

<System overview>
FIG. 1 is a block diagram showing the overall configuration of a printing system including a color conversion table creation device according to an embodiment of the present invention. The printing system 10 includes an image editing device 12, a print control device 14, and a printing unit 16. The image editing device 12 serves as a color conversion table creation device according to the embodiment, and performs a color conversion table creation process necessary for color reproduction by the printing unit 16. The image editing apparatus 12 is an apparatus that performs image processing such as color conversion processing using a color conversion table and image data processing (editing). The print image data generated by the image editing device 12 is sent to the print control device 14.

  The print control device 14 controls the printing operation by the printing unit 16 based on the print image data generated by the image editing device 12. The print control device 14 may include a halftone processing unit that converts continuous tone image data into binary or multilevel halftone image data. In the present embodiment, the image editing device 12 and the print control device 14 are illustrated as separate configurations, but a configuration in which the functions of the print control device 14 are installed in the image editing device 12 is also possible. For example, a configuration in which one computer functions as the image editing device 12 and the print control device 14 is possible.

  The printing unit 16 is an image forming unit that performs printing under the control of the printing control device 14. The printing method in the printing unit 16 and the type of color material to be used are not particularly limited. As the printing unit 16, for example, various printers such as an ink jet printer, an electrophotographic printer, a laser printer, an offset printer, and a flexographic printer can be employed. The term “printer” is understood as synonymous with terms such as a printing press, a printing apparatus, an image recording apparatus, an image forming apparatus, and an image output apparatus. As the color material, ink, toner, or the like can be used according to the type of the printing unit 16.

  Here, in order to simplify the description, a plateless digital printing machine is assumed, and a configuration in which the printing control device 14 and the printing unit 16 are combined is described as the printing device 18. A mode in which the printing control device 14 and the printing unit 16 are integrally combined to form the printing device 18 is also possible. The printing control device 14 and the printing unit 16 are configured as separate devices, and wired or wireless. A mode in which signals are exchanged by communication connection is also possible.

  When a plate-type printing machine using a printing plate is used as the printing unit 16, the system configuration includes a plate making device (not shown) such as a plate recorder that creates a printing plate from image data in addition to the printing control device 14. . In this case, a combination of a plate making device (not shown), the print control device 14, and the printing unit 16 corresponds to the printing device 18.

  The printing system 10 of this embodiment can form a color image using four colors of ink of cyan (C), magenta (M), yellow (Y), and black (K) as an example of the printing device 18. An ink jet printer is used. However, the number of ink colors and combinations thereof are not limited to this example. For example, in addition to CMYK four colors, a mode in which light color inks such as light cyan (LC) and light magenta (LM) are added, and a mode in which special color inks such as red and green are used are also possible.

  The image editing device 12 includes an image data input unit 20, an image data storage unit 22, an image processing unit 24, and a control unit 26. The image editing apparatus 12 includes an image reading unit 30, a colorimeter 32, a display unit 34, and an input device 36. The image editing apparatus 12 can be realized by a combination of computer hardware and software (program). The image editing device 12 can be realized as a function of a RIP (Raster Image Processor) device.

  The image data input unit 20 is a data acquisition unit for taking in the original image data 40. The image data input unit 20 can be configured by a data input terminal that takes in the document image data 40 from an external or other signal processing unit in the apparatus. As the image data input unit 20, a wired or wireless communication interface unit may be employed, a media interface unit for reading and writing an external storage medium (removable disk) such as a memory card, or the like. An appropriate combination of embodiments may be used.

  The target printed matter 42 is a color sample printed matter of a target color to be reproduced, and is given as an actual color sample. The document image data 40 is digital image data representing the image content to be printed. In this example, the document image data 40 is image data indicating the pattern of the document image of the target printed matter 42. The document image data 40 and the target printed material 42 are provided from a print requester (client). The document image data 40 may be data of an entire image indicating the entire image content on the printing surface of the target printed matter 42, or image part (document component) data as a part of an image recorded on the printing surface. It may be.

  The data format of the document image data 40 is not particularly limited. In this example, 8-bit (256 gradations) image data for each CMYK color is used as the original image data 40. However, the original image data 40 is not limited to the CMYK signal, but may be an RGB signal format or a combination format of a CMYK signal and a special color signal. Good. Further, the number of gradations (number of bits) of the signal is not limited to this example.

  The image data storage unit 22 is means for storing document image data 40 acquired via the image data input unit 20. Document image data 40 captured from the image data input unit 20 is stored in the image data storage unit 22.

  The image reading unit 30 reads a printed matter such as the target printed matter 42 or the printed matter 50 printed by the printing apparatus 18, converts an optical image into electronic image data, and generates read image data as a color image representing the read image. . For example, a color image scanner capable of outputting the read image as RGB image data can be used for the image reading unit 30. As the image reading unit 30 of this example, a scanner capable of acquiring read image data represented by image signals of R / G / B color components is used. A read image acquired from the image reading unit 30 may be referred to as a “scanned image”. A camera can be used instead of the scanner.

  The image reading unit 30 functions as a unit that acquires read image data of the target printed matter 42. Further, the image reading unit 30 functions as a unit that reads the printed matter 50 printed by the printing device 18 and acquires the read image data of the printed matter 50. The read image data acquired via the image reading unit 30 is sent to the image processing unit 24.

  The function of loading the read image data obtained by the image reading unit 30 into the image processing unit 24 corresponds to the “function of acquiring read image data”.

  The image processing unit 24 performs a color conversion table creation process based on the read image data acquired from the image reading unit 30 and the document image data 40. The image processing unit 24 has a function of performing color conversion processing using the color conversion table on the document image data 40 and generating image data to be transferred to the printing apparatus 18. The image processing unit 24 has a function of performing processing such as resolution conversion and gradation conversion on the document image data 40 and the read image data as necessary. Details of processing contents in the image processing unit 24 will be described later.

In addition, the printing system 10 of the present example includes a colorimeter 32 (corresponding to a “colorimetric unit”) in order to increase the accuracy of color information of an image read by the image reading unit 30. A spectrocolorimeter is used as the colorimeter 32. The spectrocolorimeter measures the reflectance of the visible light wavelength region at a predetermined wavelength increment, calculates the XYZ value using the XYZ color matching function representing the human visual spectral sensitivity, and obtains the colorimetric value To do. The spectrocolorimeter used as the colorimeter 32, for example, measures the reflectance in the wavelength range of 380 nm to 730 nm, which is the wavelength range of visible light, with a wavelength step size (wavelength step) of 10 nm to obtain a colorimetric value. . The XYZ values obtained from the colorimeter 32 can be converted into color coordinate values in a device-independent color space such as an L ^* a ^* b ^* color system by a known conversion formula.

In this embodiment, an example in which an L ^* a ^* b ^* color system is used as a color system (color coordinate system) of a device-independent color space that represents a target value of a color will be described. It is not limited. For example, XYZ color system (stimulus value Y including luminance (brightness), color stimulus value X, Z), Yxy color system (luminance Y, chromaticity coordinates x, y), L ^* U ^* v ^{* In} addition to the color system, the HSV color system (hue H (hue), saturation S (saturation), lightness V (value) or B (brightness)), HLS color system (hue H (hue) ), Saturation S (saturation), luminance L (luminance)), and YCbCr color system (luminance Y, color difference Cb, Cr) can be used.

In this specification, in order to simplify the notation, the color space of the L ^* a ^* b ^* color system is denoted as “Lab color space”, and the chromaticity value represented by the coordinate value of the Lab color space is denoted as “Lab value”. ". In addition, image data in which the image signal value of each pixel is described by a Lab value may be referred to as a “Lab image”.

  Information on the colorimetric values obtained from the colorimeter 32 is sent to the image processing unit 24. The image processing unit 24 creates a color conversion table by taking into consideration information of colorimetric values acquired from the colorimeter 32 in addition to the read image data obtained from the image reading unit 30.

  The control unit 26 controls the operation of each unit of the image editing device 12. The display unit 34 and the input device 36 function as a user interface (UI). The input device 36 may employ various means such as a keyboard, a mouse, a touch panel, and a trackball, and may be an appropriate combination thereof. In addition, the form by which the display part 34 and the input device 36 are comprised integrally like the structure which has arrange | positioned the touch panel on the screen of the display part 34 is also possible.

An operator uses the input device 36 while viewing the contents displayed on the screen of the display unit 34, inputs printing conditions, selects an image quality mode, specifies a colorimetric position, inputs / edits attached information, searches information, and the like. Various information can be input. The input contents and other various information are displayed on the display unit 3.
4 can be confirmed through the display.

  FIG. 2 is a block diagram showing an overall outline of the printing system 10. In FIG. 2, the same elements as those described in FIG. The printing system 10 of this example performs color matching so that the printing device 18 can obtain a printed material 50 that reproduces the same color as the target printed material 42 based on the given target printed material 42 and the original image data 40. Is provided. The “equivalent color” includes an acceptable range that can be satisfied as a substantially equivalent range of color differences that the client can accept.

  In order to realize such color matching, the printing system 10 includes an image reading unit 30. Further, as shown in FIG. 2, the printing system 10 includes read image data obtained from the image reading unit 30 and original image data 40. An image association unit 62 that performs alignment processing, a first color conversion unit 64 that performs color conversion processing on the read image data, and post-color conversion reading that has undergone color conversion processing by the first color conversion unit 64 And a target profile creation unit 66 that creates a color conversion table of the target profile from the correspondence between the image data and the document image data 40.

  The first color conversion unit 64 converts the signal value of the color component in the device-independent color space (Lab in this example) from the read image data represented by the signal value of the color component in the device-dependent color space (RGB in this example). The image data is converted into read image data after color conversion represented by

  The first color conversion unit 64 uses a color conversion table (corresponding to a “first color conversion table”) of the scanner profile 68 to perform color conversion processing (RGB → Lab conversion) from RGB values to Lab values. I do. The scanner profile 68 is a color conversion table (“first color conversion table”) indicating the correspondence between RGB values, which are read image signal values in the device-dependent color space obtained from the image reading unit 30, and device-independent Lab values. )including. Although the Lab color space is used as the device-independent color space here, other device-independent color spaces can also be used. The color space of the read image signal (RGB) obtained from the image reading unit 30 corresponds to the “first color space”, and the device-independent color space exemplified by the Lab color space corresponds to the “second color space”. To do. The function of color conversion by the first color conversion unit 64 corresponds to the “first color conversion function”.

  The printing system 10 obtains from the colorimeter 32 the colorimetric position association unit 70 that performs processing for associating the colorimetric position from which the colorimetric value is obtained by the colorimeter 32 with the position in the document image data 40. A first profile correction unit 72 that corrects the scanner profile 68 using the measured colorimetric value. Instead of or in addition to the first profile correction unit 72, a configuration including a chromaticity value replacement unit 74 for directly correcting the chromaticity value of the Lab image after color conversion by the first color conversion unit 64 is also possible.

  The image association unit 62, first color conversion unit 64, target profile creation unit 66, colorimetric position association unit 70, first profile correction unit 72, and chromaticity value replacement unit 74 will be described with reference to FIG. It is included in the image processing unit 24 of the image editing apparatus 12.

  As shown in FIG. 2, the image processing unit 24 includes a second color conversion unit 80 that performs color conversion of the document image data 40, a second profile correction unit 82, and a difference chromaticity value calculation unit 84. And are included.

  The second color conversion unit 80 performs conversion processing of the document image data 40 using the target profile 92 conforming to the ICC profile format and the printer profile 94, and an image signal in a data format suitable for the printing apparatus 18. Is generated. Here, an example of generating an output device signal in the CMYK signal format as an image signal in a data format suitable for the printing apparatus 18 will be described.

  The target profile 92 is also called an input profile. The color conversion table of the target profile 92 (referred to as “input color conversion table”) is a CMYK → which defines a target color (target color) of the CMYK signal of the document image data 40 in a device-independent color space (here, Lab space). 6 is a color conversion table describing Lab conversion relationships. The color space (CMYK color space here) of the document image data 40 corresponds to the “third color space”.

  The printer profile 94 is also called an output profile. The color conversion table (referred to as “output color conversion table”) of the printer profile 94 is a color conversion table that defines the correspondence between the CMYK signal output to the printing apparatus 18 and the Lab value of the output color by the printing apparatus 18. The output color conversion table is a table describing the conversion relationship (Lab → CMYK) to the output CMYK value corresponding to the Lab value to be reproduced.

  The difference chromaticity value calculation unit 84 reads the target chromaticity value (Lab value of the target printed matter 42) generated by color conversion from the read image data of the target printed matter 42 by the first color converting unit 64 and the printed matter 50. It is a calculation part which calculates the difference chromaticity value (Lab difference) showing the difference of the printing chromaticity value (Lab value of the printed matter 50) produced | generated from image data.

  The difference information calculated by the difference chromaticity value calculation unit 84 is provided to the second profile correction unit 82. The second profile correction unit 82 performs a process of correcting the target profile 92 based on the difference information. Note that the second profile correction unit 82 is not limited to the configuration for correcting the target profile 92, but may be configured to correct the printer profile 94. Alternatively, the second profile correction unit 82 creates a color correction profile 96 based on the difference information, and combines the target profile 92, the color correction profile 96, and the printer profile 94. The color conversion table can be modified.

  In the printing system 10 of the present embodiment, the operation of performing color matching between the target printed material 42 and the printed material 50 using the image reading unit 30 can be broadly divided into the following two stages.

  The first step is to estimate the target profile by reading the target printed matter 42 with the image reading unit 30, that is, to create the target profile.

  In the second stage, each of the target printed matter 42 and the printed matter 50 printed by the printing apparatus 18 is read by the image reading unit 30 and applied to the second color converting unit 80 based on these reading results. Is to improve the color matching accuracy.

  The configuration corresponding to the first stage is referred to as “first main configuration”, and the configuration corresponding to the second stage is referred to as “second main configuration”. Hereinafter, the first main configuration and the second main configuration will be described. Each will be described in more detail.

<About the first main configuration>
FIG. 3 is a block diagram showing the flow of processing in the first main configuration. In the drawing, the document image data 40 is described as CMYK, the read image data is described as RGB, and the chromaticity value is labeled as Lab. However, the color space to be applied in implementing the present invention is not limited to this example. The document image data 40 may be RGB image data, CMY image data, or image data in which a CMYK signal and a special color signal are combined.

  The chromaticity values expressed in the device-independent color space may also be values in the XYZ color system, the Luv color system, and other color systems. The same applies to the arbitrary color space.

  As shown in FIG. 3, the target profile creation process according to the first main configuration is performed in the following procedure.

  [Procedure 1] The target printed matter 42 is read by the image reading unit 30 (target printed matter image reading step), and the read image data is obtained (target printed matter read image data obtaining step). In this example, an RGB image is obtained as read image data. The acquired read image data is sent to the image association unit 62.

  [Procedure 2] The image association unit 62 performs processing for associating the positional relationship between the read image data and the document image data 40 (image association step). It should be noted that the step of taking in the original image data 40 (original image data acquisition step) may be before or after the read image data acquisition step of the target printed matter.

  In the image association unit 62, the correspondence between the pixel position of the original image and the read image is specified, and data indicating the correspondence between the signal value (CMYK value) of the original image data and the signal value (RGB value) of the read image data ( “Correspondence data between original image and read image”) is obtained.

  [Procedure 3] The first color conversion unit 64 uses the first color conversion table 68A to convert the RGB values of the read image data into Lab values (“first color conversion step”). The first color conversion table 68A is the color conversion table of the scanner profile 68 described with reference to FIG. 2, and defines the correspondence between the read image data signal value and the chromaticity value (Lab value). That is, the first color conversion table 68A is a table that defines an RGB → Lab conversion relationship for converting an input RGB signal into an output Lab value. The first color conversion unit 64 converts the RGB values of the read image data into chromaticity values in a device-independent color space.

  [Procedure 4] Through procedures 2 and 3, data indicating the correspondence between the document image signal (CMYK value) and the chromaticity value (Lab value) ("document image signal and chromaticity value correspondence data") is obtained. It is done. Based on this “document image signal and chromaticity value correspondence data”, the second color conversion table creation unit 66A creates the second color conversion table 92A (“second color conversion table creation step”). ").

  The second color conversion table creation unit 66A corresponds to the target profile creation unit 66 described with reference to FIG. The second color conversion table creation unit 66A corresponds to a “color conversion table creation unit”. The second color conversion table 92A created by the second color conversion table creation unit 66A (see FIG. 3) has a CMYK → Lab conversion relationship for converting CMYK signals of document image data into chromaticity values (Lab values). It is a specified table. The second color conversion table 92A corresponds to a target profile representing a target color, and can be used as a color conversion table of the target profile 92 applied to the second color conversion unit 80 described with reference to FIG.

<< Modification >>
FIG. 4 shows a modification of the configuration shown in FIG. 4, elements that are the same as or similar to those described in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  The configuration shown in FIG. 4 is a configuration in which the processing order of the image association unit 62 and the first color conversion unit 64 is changed compared to the configuration shown in FIG. In the example of FIG. 4, RGB read image data acquired from the image reading unit 30 is subjected to RGB → Lab conversion processing (“first color conversion processing step”) by the first color conversion unit 64. Thereafter, an image association process between the Lab image (read chromaticity value image) of the obtained read image and the document image data 40 is performed. The configuration shown in FIG. 4 can achieve the same effects as the configuration shown in FIG.

  As shown in FIG. 4, converted data obtained by performing color conversion processing by the first color converting unit 64 on the read image data obtained from the image reading unit 30 is referred to as “read chromaticity value image data. "

<About the second main configuration>
FIG. 5 is a block diagram showing a second main configuration. In FIG. 5, the same or similar elements as those described in FIGS. 1 to 4 are denoted by the same reference numerals, and the description thereof is omitted. The “third color conversion table creation unit 102” in FIG. 5 is a processing unit corresponding to the differential chromaticity value calculation unit 84 and the second profile correction unit 82 illustrated in FIG.

  Although not shown in the drawings, as with the first main configuration described with reference to FIGS. 3 and 4, the second main configuration includes the image association unit 62 and the first color of the configuration illustrated in FIG. A configuration in which the processing order of the conversion unit 64 is changed can be employed, and even when such a configuration is employed, the same effect as in FIG. 5 can be obtained.

  The procedure of the process according to the second main configuration shown in FIG. 5 will be described with reference to the flowchart of FIG. In the second main configuration shown in FIG. 5, first, an input color conversion table and an output color conversion table are set in the second color conversion unit 80 (step S110 in FIG. 6). The input color conversion table is the color conversion table of the target profile 92 described in FIG. 2, and the output color conversion table is the color conversion table of the printer profile 94.

  The input color conversion table and the output color conversion table set in step S110 in FIG. 6 are color conversion tables given as initial settings in the second color conversion unit 80. At this time, as the input color conversion table, it is preferable to use the “second color conversion table 92A” created by the first main configuration described in FIG. However, the input color conversion table of a standard profile such as Japan Color (registered trademark) is not necessarily limited to the second color conversion table 92A, and the color conversion table created in the past in the printing system 10 can be used. It is also possible to apply. As the output color conversion table, a table defined for each printing apparatus 18 according to the type of printing paper to be used can be used.

  After the input color conversion table and the output color conversion table are set in the second color conversion unit 80, the color conversion of the document image data 40 is performed by the second color conversion unit 80 using these color conversion tables, and the printing apparatus 18 is generated (step S112 in FIG. 6, “second color conversion process”).

  In this example, the CMYK document image data 40 is converted into CMYK print image data using the input color conversion table and the output color conversion table of the second color conversion unit 80.

  The print image data generated by the second color conversion unit 80 is sent to the printing device 18, and printing is performed by the printing device 18 (step S114 in FIG. 6, “printing process”). The printed matter 50 is obtained by this printing step (step S114).

  The obtained printed matter 50 is compared with the target printed matter 42, and it is determined whether or not the printed matter 50 in which the target color reproduction is achieved is obtained (step S118). Examples of the determination method in step S118 include the following two methods. That is, the first example of the determination method is a method of determining by visual comparison between the printed material 50 and the target printed material 42. A second example of the determination method is a method of quantitatively determining based on a difference between chromaticity values acquired by reading the printed material 50 and the target printed material 42 by the image reading unit 30.

  As a further specific example of the second example of the determination method, for example, the average color difference or the maximum color difference is calculated, and if the average color difference or the maximum color difference is below a certain threshold value, it is determined that the target color reproduction has been achieved. . As another specific example, both the average color difference and the maximum color difference may be calculated, and the average color difference and the maximum color difference may be combined for determination. In this case, for example, when the average color difference is equal to or smaller than the first threshold value and the maximum color difference is equal to or smaller than the second threshold value, it can be determined that the target color reproduction is achieved. Alternatively, an evaluation function for obtaining another evaluation value (index value) by combining the average color difference and the maximum color difference is defined, and the evaluation value obtained from the evaluation function is compared with a threshold value defined as a criterion. Then, it may be determined whether or not the target color reproduction has been achieved.

  That is, in the second example of the determination method, the determination is based on the difference between the chromaticity values obtained in step S124 and step S134 described later. By installing such a calculation function and a determination function for making a quantitative determination, an automatic determination process can be realized.

  Instead of or in combination with the determination method by visual comparison (first example), a quantitative determination method (second example) based on the difference in chromaticity values can be employed.

  If it is determined in step S118 that the printed material 50 having achieved the same color reproduction as the target printed material 42 is obtained, the determination in step S118 is Yes, and the color matching process can be ended.

  On the other hand, if it is determined in step S118 that the printed material 50 of the target color has not been obtained, the determination in step S118 is No, the process proceeds to step S120 in FIG. 6, and the printed material 50 is read by the image reading unit 30. Then, the read image data of the printed matter 50 is acquired (step S120 in FIG. 6). Step S120 corresponds to a “printed image reading process” or a “printed image data acquisition process”.

  In this example, an RGB image is obtained as read image data, and the acquired read image data is sent to the image association unit 62. The image association unit 62 performs image association processing for associating the positional relationship between the read image data of the printed matter 50 (referred to as “printed matter read image data”) and the document image data 40 (step S122 in FIG. 6). ). The step of taking in the original image data 40 (original image data acquisition step) may be performed before or after the read image data acquisition step of the printed matter. However, if the document image data 40 has already been imported into the system by the first main configuration described with reference to FIG. 3, it is not necessary to import the document image data 40 again, and the image data storage unit 22 (see FIG. 1). The document image data 40 may be read from the document.

  The correspondence between the document image and the pixel position of the read image is specified in the image association unit 62, and the correspondence between the signal value (RGB value) of the printed material read image data corresponding to the signal value (CMYK value) of the document image data is determined. The data shown is obtained.

  The first color conversion unit 64 uses the first color conversion table 68A to convert the RGB values into Lab values for the printed material read image data that has undergone the image association processing by the image association unit 62. (Step S124 in FIG. 6, “first color conversion step”). Thereby, the chromaticity value (Lab value) of the printed material read image data is obtained.

  Similar to the steps S120 to S124 for the printed matter 50, the read image data is obtained for the target printed matter 42 (step S130), the correspondence between the document image data and the read image data (step S132), and the color to the chromaticity value. Conversion (step S134) is performed.

  That is, the target printed matter 42 is read by the image reading unit 30, and the read image data of the target printed matter 42 is acquired (step S130 in FIG. 6). Step S <b> 130 corresponds to a “target printed matter image reading step” or a “target printed matter read image data acquisition step”. The acquired read image data of the target printed matter 42 (referred to as “target printed matter read image data”) is sent to the image association unit 62. The image associating unit 62 performs an image associating process for associating the positional relationship between the target printed matter read image data and the document image data 40 (step S132 in FIG. 6).

  The correspondence between the pixel position of the original image and the read image is specified in the image association unit 62, and the correspondence between the signal value (RGB value) of the target printed material read image data corresponding to the signal value (CMYK value) of the original image data. Is obtained.

  For the target printed matter read image data that has undergone the image association processing by the image association unit 62, the first color conversion unit 64 performs a process of converting from RGB values to Lab values using the first color conversion table 68A. This is performed (step S134 in FIG. 6, “first color conversion step”). Thereby, the chromaticity value (Lab value) of the target printed matter read image data is obtained.

  In addition, the process of step S130-S134 can be performed before the process of step S120-S124, or can also be performed in parallel with the process of step S120-S124. Further, when the “second color conversion table 92A” has been created by the steps 1 to 4 of the first main configuration described in FIG. 3, information on the chromaticity value of the target printed material read image data has already been obtained. Therefore, steps S130 to S134 can be omitted.

  Thus, the chromaticity value of the target printed matter read image data corresponding to the original image data 40 (that is, the chromaticity value of the target printed matter 42) and the chromaticity value of the printed matter read image data (ie, the chromaticity value of the printed matter 50). Information is obtained, and color conversion is performed based on the difference between the chromaticity value of the target printed matter 42 and the chromaticity value of the printed matter 50 from the relationship between the original image signal, the chromaticity value of the target printed matter 42, and the chromaticity value of the printed matter 50. A process of creating a table is performed (step S146 in FIG. 6).

  The processing unit that creates the color conversion table in step S146 is the “third color conversion table creation unit 102” in FIG. The color conversion table created by the third color conversion table creation unit 102 is used by the second color conversion unit 80, and the third color conversion table creation unit 102 is the second color conversion unit 80. Any one of an input color conversion table, an output color conversion table, and a color correction table of a color correction profile 96 (see FIG. 2) used in the above is created.

  In this way, the color conversion table created by the third color conversion table creation unit 102 is applied to the second color conversion unit 80 (step S148 in FIG. 6), the process returns to step S112, and the processes after step S112 are repeated. . Note that, in the repeated processing, the processing in steps S130 to S134 related to reading the target printed matter 42 is not necessary.

  According to the second main configuration described with reference to FIGS. 5 and 6, the color conversion table applied to the second color conversion unit 80 can be improved to a more appropriate table, and the accuracy of color conversion is further improved. Can be made.

<Description of each part>
Next, the function of each part in the first main configuration (FIGS. 3 and 4) and the second main configuration (FIG. 5) will be described in more detail.

[Regarding Image Reading Unit 30]
In the first main configuration shown in FIGS. 3 and 4, the image reading unit 30 does not read the printed material 50 and reads only the target printed material 42. That is, in the first main configuration, the target profile is created only from the read result of the original image data 40 and the target printed matter 42 without printing the printed matter 50.

  On the other hand, in the second main configuration shown in FIG. 5, the image reading unit 30 reads two types of printed materials, that is, the target printed material 42 and the printed material 50 printed by the printing device 18. That is, in the second main configuration, the original image data 40 is printed by the printing device 18, the obtained printed material 50 is read, and the given target printed material 42 is read. The color conversion table of the second color conversion unit 80 is corrected so that the difference becomes smaller.

[About the image association unit 62]
The image association unit 62 associates the original image data 40 with the image position (that is, pixel position) of the read image data obtained by reading the printed material (the target printed material 42 or the printed material 50).

  The read image data here corresponds to either an RGB image obtained from the image reading unit 30 or a chromaticity value image (Lab image) obtained by color-converting the RGB image by the first color conversion unit 64. . The read image data in the configuration shown in FIG. 3 is an RGB image, and the read image data in the configuration shown in FIG. 4 is a chromaticity value image (Lab image).

  A known image alignment method can be used for the process of associating (positioning) the image position between the document image data 40 and the read image data. For example, the method described in paragraphs [0064] to [0068] of Patent Document 1 can be used as an image alignment method.

  FIG. 7 is a block diagram showing a specific example of image alignment processing in the image association unit 62. The image association unit 62 includes a geometric correspondence relationship estimation unit 112 and a geometric conversion unit 114. The geometric correspondence relationship estimation unit 112 takes in the original image data 40 and the read image data 120 and estimates the geometric correspondence relationship between these two images. The geometric correspondence includes at least one element among the image displacement amount, the rotation angle, and the scaling factor between the two images to be compared.

  Based on the geometric correspondence relationship estimated by the geometric correspondence relationship estimation unit 112, the geometric conversion unit 114 performs a geometric conversion process for matching one or both of the two images. For example, the read image data may be subjected to geometric conversion, and the original image data 40 may be configured not to perform geometric conversion. Moreover, affine transformation can be applied as an example of geometric transformation.

  For example, (a) a method using a marker, (b) a method using pattern matching, (c) a method using a phase-only correlation method can be used to estimate the geometric correspondence between two images. Hereinafter, the description in Patent Document 1 will be used.

(A) Method Using Marker A printed matter in which markers indicating reference positions called so-called “register marks” in the printing industry are arranged at the four corners and the center of each side is output. When such a printed matter with a marker is read, the displacement amount of the marker position can be measured to obtain the displacement amount, rotation angle, and scaling factor between images.

  For example, four to six registration marks (markers) are formed on one printed matter. By comparing the positional deviation between the marker on the original image data and the marker on the read image data of the printed material, the geometric conversion parameter can be obtained.

  A geometric conversion parameter is obtained by obtaining a correspondence relationship between a point indicating the position of the feature point of the marker in the document image data and a point indicating the position of the feature point of the marker in the read image data. Here, it is known to match two point patterns by performing, for example, affine transformation on one of the two images. Therefore, in order to obtain the geometric transformation parameter, it is only necessary to find an optimal affine parameter that approximates each position of the two point patterns. For example, an affine parameter evaluation function for affine transformation of the marker feature point in the read image data to the marker feature point in the document image data is defined, and the affine parameter when the evaluation function is minimized is used as the geometric transformation parameter. .

(B) Method Using Pattern Matching Method A template matching method is an example of a method for estimating only the displacement amount. In the template matching method, one image is used as a template, the degree of coincidence with the other image is obtained while gradually shifting the position, and the position with the highest degree of coincidence is detected. When the geometric transformation cannot be limited to only displacement, it is necessary to use in combination with a method for estimating the rotation angle (such as Hough transform) or a method for estimating the amount of magnification (such as multi-scale analysis).

  In the block matching method using template matching, one image is divided into blocks, and the displacement amount can be obtained by detecting the position having the highest degree of coincidence with the other image for each block. In the block matching method, it is also possible to estimate the rotation angle and magnification from the displacement amount for each block.

(C) Method using phase only correlation method Examples of methods for obtaining displacement, rotation angle, and scaling factor with high accuracy include phase only correlation (POC) and rotation invariant phase only correlation (RIPOC). Invariant Phase Only Correlation). The phase only correlation method uses a phase image obtained by subjecting an image to a discrete Fourier transform, and detects the position where the correlation between the two phase images obtained from the two images to be compared is the highest. This is a method for obtaining a displacement amount. The rotation-invariant phase-only correlation method is such that the rotation angle and the scaling factor can be detected as a displacement amount on the converted phase image by logarithmic polar coordinate conversion of the phase image.

  After obtaining the geometric transformation parameters by the above-described exemplary methods (a) to (c), the geometric transformation unit 114 performs geometric transformation on the read image data 120 (or the original image data 40). In the case where the pixels before and after conversion do not correspond one-to-one due to sub-pixel precision shift, some rotation, or scaling with a real value at the time of conversion, the pixel value may be derived appropriately using a pixel interpolation method. Examples of pixel interpolation methods include bilinear methods and bicubic methods.

  In this way, the positional relationship with the document image data 40 is determined, and the associated read image data 122 is obtained. The associated read image data 122 is sent to the first color conversion unit 64 (see FIGS. 2 to 5).

[Pre-processing for image matching (positioning)]
If the resolution of the document image data 40 and the resolution of the read image data 120 are different, the image association unit 62 may perform resolution conversion on the read image data 120 so as to match the resolution of the document image data 40. preferable. The image association unit 62 includes a resolution conversion unit (not shown) for performing resolution conversion processing.

  Further, when the color space of the document image data 40 and the read image data 120 is different, for example, when the document image data 40 is a CMYK image and the read image data 120 is an RGB image, the image association unit 62 Before image alignment (association), it is preferable to convert both images to gray scale and convert them to the same color space.

  Gray scale conversion can be realized, for example, by converting the read image data 120 into a Lab value using the scanner profile 68 (see FIG. 2) and obtaining a monochrome image in which only the L value (lightness) is extracted. For the document image data 40, there is no color profile of the target printed matter 42 when the target profile is created by the first main configuration (FIGS. 3 and 4). For example, Japan Color (registered trademark) ) And other typical profiles can be used.

  In addition, even if both the original image data 40 and the read image data 120 are converted to grayscale, it is assumed that pixel values (density values) are different. Therefore, an edge extraction process is further performed on the grayscale image, Registration may be performed after conversion to a binary edge image. For the edge extraction process, a known Sobel method or Prewitt method can be used.

  Also, since it is assumed that the edge thickness of the two edge images may be different, further thinning processing is performed on each edge image, and alignment is performed after aligning the edge thickness. Also good. For the thinning process, a known Hilditch method or Tamura method can be used.

  As described above, when the color space of the image is different between the document image data 40 and the read image data, it is preferable to perform preprocessing for alignment so that the geometric correspondence of the images can be easily estimated. Note that preprocessing may be performed even when the document image data 40 and the read image data are in the same color space.

  Furthermore, the target printed matter 42 is the actual printed matter (printed matter actually shipped) printed by a printing device other than the printing device 18, and the target printed matter 42 and the original image data 40 do not correspond one-to-one. There are cases. For example, the following example can be given as a case where the target printed matter 42 and the document image data 40 do not have a one-to-one correspondence.

  <Example 1>: When the target printed material 42 is a printed material in which a large number of the same document image data 40 are arranged on the same printing surface.

  <Example 2>: When the target printed matter 42 is a printed matter in which the document image data 40 and image data that is not a color matching target (other image data different from the document image data 40) are arranged on the same printing surface. Note that disposing a plurality of different image data on the same printing surface is called “heterogeneous imposition” or “ganging”.

  <Example 3>: When the document image data 40 constitutes a part of the target printed matter 42 (a part of the design / layout).

  If the target printed matter 42 and the document image data 40 do not have a one-to-one correspondence as exemplified in <Example 1> to <Example 3> above, the document image data to be noticed from among the read images of the target printed matter 42 It is useful to perform a partial image extraction process for extracting a partial image corresponding to 40.

  Here, as a further specific example of <Example 1>, a case will be described in which the target printed matter 42 is a printed matter in which the same original image data 40 is nested (imposed) in the same print surface.

  An example is shown in FIGS. FIG. 8A shows an example of original image data, and FIG. 8B shows an example of a target printed matter. The target printed matter shown in FIG. 8B is a printed matter obtained by printing a plurality of document image data shown in FIG. 8A in a nested manner (imposition) on the printing surface.

  In such a case, the read image data of the target printed matter is not used as it is, but a partial image corresponding to the original image data is extracted in advance in the read image data before alignment by the image association unit 62. preferable.

  As a method of extracting a partial image, a method of automatically extracting a partial image corresponding to a document image by using known pattern matching, or displaying a read image on the display unit 34 as a monitor and allowing the user to read the document A method of manually specifying the range of the partial image corresponding to the image can be considered.

  Not only in the case of <Example 1> but also in the case of <Example 2> and <Example 3>, it is useful to perform the partial image extraction process.

  The partial image extraction process described above is unnecessary if the original image data 40 and the target printed matter 42 have a one-to-one correspondence, for example, when a color sample for one original image is provided from the client. is there.

  FIG. 9 is a block diagram of a configuration for performing image association processing including the preprocessing described above. The image association unit 62 shown in FIG. 9 includes a document correspondence image extraction unit 130 (corresponding to an “image extraction unit”), a gray scale conversion unit 132, an edge extraction unit 134, a thinning unit 136, and a geometric correspondence. The relationship estimation part 112 and the geometric transformation part 114 are provided.

  The document corresponding image extraction unit 130 corresponds to the document image data 40 from the read original image data 140 obtained by reading the target print 42 on which a plurality of images are arranged as shown in FIG. 8B. Processing to extract an image is performed. The read original image data 140 is read image data generated by reading the entire printing surface of the target printed material as shown in FIG. The read original image data 140 may be an RGB image or a Lab image.

  The partial image data extracted by the document corresponding image extraction unit 130 becomes the read image data 120 to be compared with the document image data 40.

  The gray scale conversion unit 132 performs processing for converting each of the document image data 40 and the read image data 120 into gray scale. The edge extraction unit 134 performs edge extraction processing from the grayscale image. The thinning unit 136 performs a thinning process on the edge image generated by the edge extraction unit 134.

  The edge image thinned by the thinning unit 136 is input to the geometric correspondence estimation unit 112, and the geometric correspondence estimation unit 112 specifies the geometric correspondence between the document image data 40 and the read image data 120. Using the geometric correspondence relationship thus obtained, the geometric conversion unit 114 performs a geometric conversion process on the read image data 120 to obtain associated read image data 122.

  The association processing function by the image association unit 62 corresponds to an “image association function”. If the original image data 40 and the print image of the target print 42 have a one-to-one correspondence, the read original image data 140 in FIG. 9 is handled as the read image data 120 as it is.

[About the first color conversion unit 64]
The first color conversion unit 64 performs processing for converting data of a read image (for example, an RGB image) acquired from the image reading unit 30 into data in a device-independent color space. As described with reference to FIG. 2, in this example, the image reading unit uses an RGB → Lab conversion table as a color conversion table (corresponding to a “first color conversion table”) of the scanner profile 68 prepared in advance. 30 read image signal values (RGB) are converted into chromaticity values (Lab) in a device-independent color space.

  Here, when there are a plurality of identical image signal values in the document image data, the corresponding read image is affected by noise of the image reading unit 30, dust adhering to the printed matter, or scratches on the printed matter. It is conceivable that the chromaticity values of are different. Therefore, in order to reduce the influence of such noise and the like, it is preferable to average the chromaticity values of the read images corresponding to the same document image signal value.

[Regarding Target Profile Creation Unit 66 (Second Color Conversion Table Creation Unit 66A)]
Through the processing of the image reading unit 30, the image association unit 62, and the first color conversion unit 64, the image signal value (CMYK value in this example) of each pixel in the document image data 40 and the target printed matter 42. Thus, data representing a correspondence relationship with the chromaticity value (Lab value in this example) of each pixel in the read image data is obtained. The target profile creation unit 66 (FIG. 2), that is, the second color conversion table creation unit 66A (FIG. 3), based on this “document image signal and chromaticity value correspondence data”, the image signal value (CMYK). ) To a chromaticity value (Lab), a color conversion table that defines a conversion relationship (CMYK → Lab) is created.

  In the case of a conventional printing system, when creating such a color conversion table, generally, using a color chart, the correspondence between image signal values regularly arranged in the entire color space and chromaticity values is obtained. From this correspondence, a color conversion table is created by interpolation using a predetermined interpolation method.

  On the other hand, in the present embodiment, since the target printed matter 42 that is the actual reproduction target and the original image data 40 are used as a basis, the image signal values and chromaticity values of the partial and irregular arrangement in the color space are used. It is necessary to create a color conversion table from the correspondence. Therefore, the conventional general interpolation method cannot be used. Therefore, the following method is taken.

[First Embodiment] Method for Directly Associating Correspondence Data between Original Image Signal and Chromaticity Value to Color Conversion Table Method for Directly Corresponding Original Relationship between Original Image Signal and Chromaticity Value to Grid Point in Color Space of Color Conversion Table Will be described with reference to FIGS. 10 and 11. Here, in order to simplify the description, the concept of a color conversion table for CM2 colors is shown. FIG. 10 is an example of correspondence data between the document image signal (CM) and the chromaticity value (Lab). FIG. 11 shows lattice points in the color space (here, the CM plane) of the document image data corresponding to the input side of the color conversion table.

  In FIG. 11, for each of the C axis and the M axis, the range (range, value range) that the signal value can take is represented by 0 to 100%, and lattice points are set in increments of 10% for each axis. It should be noted that when the invention is carried out, the step size of the signal of each axis that defines the lattice point is not limited to 10%. When an 8-bit integer value (0 to 255) is used as the signal value of the image signal, the signal value “0” is 0%, the signal value “255” is 100%, and a value between 0-255 is expressed in a linear form. Can be associated.

  The grid points in increments of 10% shown in FIG. 11 indicate the grid points of the original image signal on the input side in the color conversion table. The corresponding Lab value assigned to each grid point corresponds to the color conversion table.

  “ID” in FIG. 10 is an identification code for specifying the color (CM value) used in the document image data. Each of the C value and the M value represents a signal value in a range of 0 to 100%. The Lab value includes the value of each component of the L value, the a value, and the b value.

  The CM value of ID = 1 is (C, M) = (20, 90), and the Lab value corresponding to this CM value is (L, a, b) = (50, 60, −13). Is shown.

  The color of ID = 2 is (C, M) = (24, 66), and the Lab value corresponding to the CM value color of ID = 2 is (L, a, b) = (60, 36, −17). It is shown that.

  When creating the color conversion table, the corresponding chromaticity value (Lab value) is set at the grid point of the color conversion table corresponding to the document image signal value (CM value) for each ID shown in FIG.

The CM value of ID = 1 is a color corresponding to the grid point P1 in FIG. The corresponding Lab value (50, 60, −13) is set to the grid point P ₁ corresponding to ID = 1.

  For ID = 2 to 5, since there is no directly corresponding grid point, chromaticity values are set for neighboring grid points. As shown in FIG. 11, for ID = 2, 3, and 4, chromaticity values are set at the four surrounding grid points surrounding the document image signal value.

ID = 2 sets the same Lab value (60, 36, −17) for the four lattice points P ₂₁ , P ₂₂ , P ₂₃ , and P ₂₄ surrounding (C, M) = ( ₂₄ , 66). . Similarly, for ID = 3 and ID = 4, chromaticity values are set for four lattice points surrounding the document image signal value. However, as shown in ID = 3 and ID = 4, when a part of the four grid points surrounding each original image signal value overlaps and there are different chromaticity value candidates for the same grid point, the candidate Set the average chromaticity value of.

That is, four lattice points surrounding (C, M) = (35, 35) with ID = 3 are P ₃₁ , P ₃₂ , P ₃₃ , P ₃₄ , and (C, M) = (47 with ID = 4 , 23) are four lattice points P ₄₁ (= P ₃₃ ), P ₄₂ , P ₄₃ , P ₄₄ . For a grid point (P ₃₃ = P ₄₁ ) represented by (C, M) = (40,30), a chromaticity value candidate (71,9, −20) with ID = 3 and ID = Since there are 4 chromaticity value candidates (72, -4, -26), an average value (71.5, 2.5, -23) of Lab values of ID = 3 and ID = 4 is assigned.

For the other lattice points P ₃₁ , P ₃₂ , and P ₃₄ , Lab values (71, 9, -20) with ID = 3 are set. For P ₄₂ , P ₄₃ , and P ₄₄ , the Lab value (72, −4, −26) with ID = 4 is set.

For ID = 5, since the C value is “10%”, instead of “four surrounding grid points”, “two grid points” P ₅₁ , P _{52 are obtained} , and these grid points P ₅₁ , P ₅₂ On the other hand, a corresponding Lab value (89, 6, -8) is set.

  Among all the grid points in the color conversion table, grid points that are not related to the document image signal value are not used for color conversion of the document image data 40, and are set to appropriate values. For grid points indicated by white circles in FIG. 11, for example, an arbitrary value such as Lab = (100, 0, 0) can be set.

  In FIG. 10 and FIG. 11, for the sake of simplicity, the description has been given with reference to the color conversion table for two CM colors.

  In the case of two colors, the maximum number of grid points surrounding an arbitrary CM value is four, but in the case of three colors, the maximum is eight points, and in the case of four colors, the maximum is sixteen points.

  10 and 11, ID = 1 directly associates the Lab value (chromaticity value) with the grid point corresponding to the CM value, but it is slightly shifted due to calculation error or the like when referring to the color conversion table. There is also a possibility that the point is referred to and interpolated with the chromaticity value of the adjacent grid point. For this reason, it is also preferable to set the same chromaticity value not only to the directly corresponding grid points but also to adjacent neighboring grid points.

  There is no inconvenience when the original image data 40 is color-converted using the color conversion table created by the method described in the first embodiment and printed by the printing apparatus 18.

  However, if the operator further adjusts (corrects) the original image data for color adjustment by looking at the result of printing using the color conversion table created by the method of the first embodiment, inconvenience may occur. That is, when the operator adjusts the document image data 40, a desired color change may not occur, or a color change different from the color change direction intended by the operator may occur. Adjustment becomes difficult.

  In order to avoid the inconvenience when adjusting the original image data as described above, the entire color space (even the color portion not directly related to the original image data) has a corresponding chromaticity value (imagined by the operator). It is preferable that the color is close to the color) and the smoothness of the color change is ensured. In order to ensure such a smooth continuity of the entire color space, it is preferable to use a method such as those of Examples 2, 3, and 4 described below.

[Embodiment 2] Regarding a method of correcting a provisional color conversion table based on correspondence data between original image signals and chromaticity values In Embodiment 2, smoothness of corresponding color changes is secured in advance in the entire color space. A “temporary color conversion table” is prepared, and the temporary color conversion table is locally (partially) corrected using correspondence data between the document image signal and the chromaticity value.

  The “provisional color conversion table” here is, for example, any one of color conversion tables representing standard color reproduction in offset printing such as Japan Color (registered trademark), SWOP, GRACoL, Fogra, etc., if CMYK is input. Any RGB color conversion table such as sRGB or AdobeRGB can be used.

  Further, the standard color conversion table as described above and the color conversion table previously created by the method of the second embodiment are stored in the database, and the current read image 42 of the target printed matter 42 and the original image data 40 are used. It is also possible to select a color conversion table closest to the correspondence data between the newly acquired document image signal and chromaticity value from the database and use the selected color conversion table as a “temporary color conversion table”. it can. A standard color conversion table or a color conversion table created in the past corresponds to an “existing color conversion table”.

  When selecting the color conversion table closest to the “correspondence data between original image signal and chromaticity value”, the average color difference between the original image signal and the correspondence data between chromaticity values is the smallest, Those having the smallest color difference with the correspondence data of the chromaticity values are automatically extracted from the database, and can be used as a “temporary color conversion table”. In addition, when a plurality of “provisional color conversion table” candidates are extracted by automatic extraction, a configuration in which the candidates are displayed on the display unit 34 and selected by the user is also possible.

For this “provisional color conversion table”, the chromaticity values for the grid points described in the first embodiment are set. That is, for lattice points P ₁ , P _{21 to} P ₂₄ , P _{31 to} P ₃₄ , P _{41 to} P ₄₄ , and P _{51 to} P ₅₂ (see FIG. 11) corresponding to ID = 1 to 5 described in FIG. The chromaticity values are set in the same manner as in the first embodiment, and the tentative color conversion table is corrected so that the chromaticity values for the lattice points indicated by white circles in FIG. 11 remain the values of the “temporary color conversion table”. To do.

  The corrected color conversion table obtained in this way replaces the chromaticity value of the grid point locally with respect to the temporary color conversion table, so the chromaticity value between the grid point with the replaced chromaticity value and the grid point without replacement. It is expected that the continuity (smoothness) will deteriorate. For this reason, it is preferable to further smooth (smoothing) the corrected color conversion table to ensure smooth conversion of chromaticity values.

[Example 3] Method of using a color reproduction model As a color reproduction model, for example, a Neugebauer model can be used. The Neugebauer model is a reproduction color that is obtained by multiplying the area ratio of each color material by adding the chromaticity values of the multiplied colors of 0% and 100% of each color material (primary color) according to the area ratio of each color material. This is a model for obtaining the chromaticity value of. In the Neugebauer model, XYZ values are generally used as “chromaticity values”.

  Here, referring to FIG. 12, a color reproduction model will be described using an example of CMY3 color materials. If the CMY area ratio of the color to be predicted is (fc, fm, fy), the area ratio Fi (i = w, c, m, y, cm, my, yc, cmy) can be calculated as: “·” In the formula represents multiplication.

Fw = (1-fc), (1-fm), (1-fy)
Fc = fc ・ (1-fm) ・ (1-fy)
Fm = (1-fc), (1-fm), fy
Fcm = fc ・ fm ・ (1-fy)
Fmy = (1-fc) ・ fm ・ fy
Fyc = fc ・ (1-fm) ・ fy
Fcmy ＝ fc ・ fm ・ fy
Here, “w” represents the base material (printing base material) itself of a printed matter such as printing paper. The area ratio is
The coverage per unit area on the printing substrate is shown. Here, the area ratio is expressed as a value between 0 and 1. fc, fm, and fy are values grasped from the signal value (image signal value) of the image data.

  When the chromaticity value (for example, XYZ value X) of 0% and 100% of each color material is Xpi (i = w, c, m, y, cm, my, yc, cmy), the CMY area ratio ( The chromaticity value X for fc, fm, fy) can be obtained by the following equation.

  The Y and Z values of the XYZ values can be obtained in the same manner, and further the conversion from the XYZ values to the Lab values can be simplified. In addition, printing of two colors or four or more colors other than three-color printing can be similarly applied.

  In order to use this Neugebauer model for creating a color conversion table, chromaticity values of 0% and 100% of each color material are required.

  However, in this embodiment, since it is based on an actual printed matter (target printed matter 42) instead of a color chart, the image signal value (CMYK) grasped from the reading of the target printed matter 42 and the chromaticity value of the target printed matter 42 ( In the correspondence relationship of (XYZ), the color of 0% and 100% of each color material does not necessarily exist.

  Therefore, the chromaticity values (Xpi, Ypi, Zpi) corresponding to the multiplication of each color material 0% and 100% of the Neugebauer model are set as unknowns, and the image signal value (CMYK), that is, “Fi”, and the chromaticity of the target printed matter. Assume that (Xpi, Ypi, Zpi) is estimated by an optimization method using the correspondence relationship between the values (Xm, Ym, Zm) as correct data. That is, optimization is performed to find (Xpi, Ypi, Zpi) that minimizes the sum of squares of the differences shown in the following equation.

  The following expression is an expression related to X. The expressions for Y and Z can be expressed in the same way.

  Here, j is a subscript indicating an ID (that is, each pixel) of correspondence data between the image signal value (CMYK) and the chromaticity value (XmYmZm) of the target printed matter.

  As an optimization method, for example, a Newton method, a quasi-Newton method, a simplex method, or the like can be used. It is possible to use a method other than the method exemplified here, and the method to be applied is not limited.

  By using (Xpi, Ypi, Zpi) obtained by the above optimization, the chromaticity value of each grid point of the color conversion table can be calculated by the Neugebauer model.

  As described above, (Xpi, Ypi, Zpi) is estimated by the optimization calculation. If there is a color multiplied by 0% and 100% of the color material in the image signal, the corresponding chromaticity value is (Xpi) as it is. , Ypi, Zpi). Unknowns are reduced and optimization becomes easier.

  In the above description, the Neugebauer model is used. However, the following Neugebauer model with Yule-Nielsen correction can also be used. n is a so-called Yule-Nielsen correction coefficient that corrects the nonlinearity of multiplication for the Neugebauer model.

When using this model with a correction coefficient, optimization may be performed by adding n to the unknown. n may be common to XYZ values, or may be obtained as different coefficients (nx, ny, nz) for X, Y, and Z, respectively.

  In addition to this, use of Cellular-Neugebauer model, etc., which expands the color (Xpi, Ypi, Zpi), which is the basis of color prediction, to a multiplying color (for example, 0%, 40%, 100%) including the intermediate area ratio Is also possible. Further, the implementation of the present invention is not limited to the Neugebauer model. Any model that represents the relationship between the image signal and the chromaticity value may be used, and a color reproduction model other than the Neugebauer model may be used. Also, a new model can be created by formulating color reproduction (relationship between image signals and chromaticity values) with an appropriate matrix or polynomial and optimizing matrix elements and polynomial coefficients.

[Embodiment 4] Combination Method of Embodiment 3 and Embodiment 2 As Embodiment 4, a color conversion table is created by using a color reproduction model, and further, the correspondence data between the document image signal and the chromaticity value is used. There is a method of correcting the color conversion table (color conversion table created using a color reproduction model). That is, the fourth embodiment is a method in which the color conversion table created in the third embodiment is used as a “temporary color conversion table” and the method of the second embodiment is further performed.

[Second Color Conversion Unit 80]
The second color conversion unit 80 obtains a profile using the second color conversion table 92A created by the target profile creation unit 66 (that is, the second color conversion table creation unit 66A) or an appropriate profile prepared in advance. The original image data 40 is color-converted using the profile of the printing device 18 prepared in advance as an output profile as an input profile. The “appropriate profile prepared in advance” includes standard profiles such as Japan Color (registered trademark), SWOP, GRACoL, Fogra, etc. in the case of CMYK signals, for example.

  In the second main configuration described with reference to FIG. 5, the input profile initially set for the second color conversion unit 80 should be as close as possible to the color reproduction characteristics of the target printed matter 42. Therefore, it is preferable that the input profile candidates are stored in the database, and the input profile is selected based on the correspondence between the original image signal acquired by reading the target printed matter 42 and the chromaticity value. The input profile initially set for the second color conversion unit 80 may be selected such that the average color difference or the maximum color difference between the read chromaticity value and the profile chromaticity value for the document image signal is the smallest.

  FIG. 13 is a principal block diagram relating to the second color conversion unit 80.

  The image editing apparatus 12 includes a color conversion table database 160 and an input color conversion table selection unit 162. The color conversion table database 160 stores color conversion tables for standard profiles and input profiles created in the past. The color conversion table database 160 corresponds to an “input color conversion table database”.

  The input color conversion table selection unit 162 performs a process of selecting the color conversion table of the optimum input profile from the color conversion table database 160 based on the correspondence data 164 between the document image signal and the chromaticity value. The “document image signal and chromaticity value correspondence data 164” is generated through the processing by the image association unit 62 and the first color conversion unit 64 described with reference to FIGS.

  The input color conversion table selection unit 162 shown in FIG. 13 reads from the color conversion table database 160 the read chromaticity value and profile chromaticity for the original image signal based on the correspondence data 164 between the original image signal and the chromaticity value. A process is performed to select a value having the smallest average color difference or maximum color difference.

  One color conversion table selected by the input color conversion table selection unit 162 is set as the color conversion table 166 of the input profile in the second color conversion unit 80.

  The document image data 40 is converted from CMYK values to Lab values by the input profile color conversion table 166 (“input color conversion table”) in the second color conversion unit 80, and further, the output profile color conversion table 168 ( The “output color conversion table”) converts the Lab value to the CMYK value.

  Thus, the original image data 40 is converted from CMYK to CMYK by the second color conversion unit 80, and CMYK data is obtained as the print image data 170 after color conversion. In FIG. 13, the two color conversion tables (166, 168) are described as performing the color conversion process step by step. However, in actual processing, these two color conversion tables (166, 168) are integrated. Thus, it is possible to combine them into one color conversion table for CMYK → CMYK conversion. Using this integrated multi-dimensional (CMYK → CMYK) color conversion table, color conversion can be performed in a single process.

  The print image data 170 generated by the second color conversion unit 80 is passed to the printing device 18 (see FIGS. 1 and 2). The printing device 18 prints the printed matter 50 based on the print image data 170.

[About Third Color Conversion Table Creation Unit 102]
Next, the third color conversion table creation unit 102 in FIG. 5 will be described. In the second main configuration illustrated in FIG. 5, the chromaticity from the printed matter 50 is also obtained for the printed matter 50 in the same manner as the procedure for obtaining the chromaticity value from the target printed matter 42 (procedures 1 to 3 and steps S130 to S134 in FIG. 6). A procedure for acquiring a value is performed (steps S120 to S124 in FIG. 6).

  As a result, correspondence data between the chromaticity values of the original image data 40 and the target printed matter 42 is obtained, and correspondence data between the chromaticity values of the original image data 40 and the printed matter 50 are obtained. That is, the signal value of the original image data 40 (original image signal value), the chromaticity value of the target printed matter 42 (referred to as “target chromaticity value”), and the chromaticity value of the printed matter 50 (referred to as “printing chromaticity value”). Data indicating the correspondence between the three parties is obtained.

  From such correspondence data, the difference between the target chromaticity value for each signal value of the document image data 40 and the chromaticity value (print chromaticity value) of the result of actual printing can be acquired. The difference between the chromaticity values (referred to as “difference chromaticity value”) is reflected in the color conversion table of the input profile (target profile 92) or the color conversion table of the output profile (printer profile 94) in the second color converter 80. Thus, the color conversion table is corrected (see FIG. 2).

  Alternatively, the color correction profile 96 for correcting the chromaticity value between the input profile and the output profile may be inserted, and the color correction table of the color correction profile 96 may be created from the information on the difference chromaticity value. it can.

  The third color conversion table creation unit 102 (see FIG. 5) is a block including the difference chromaticity value calculation unit 84 and the second profile correction unit 82 described in FIG. The difference chromaticity value calculation unit 84 is a processing unit that calculates the difference between the target chromaticity value and the printing chromaticity value. The second profile correction unit 82 performs a process of correcting the color conversion table of the input profile or the color conversion table of the output profile, or a process of creating a color correction table of the color correction profile 96.

[Example of how to modify the color conversion table of the input profile]
As a specific example of the third color conversion table creation unit 102, an example of correcting the color conversion table of the input profile will be described. In this example, a conversion table of CMYK → Lab is used as the color conversion table of the input profile.

  If the value obtained by subtracting the print chromaticity value from the target chromaticity value (difference) is the differential chromaticity value (difference chromaticity value = target chromaticity value-print chromaticity value), the grid point of the color conversion table of the input profile Then, the difference chromaticity value is added to correct the chromaticity value (the value on the output side of the color conversion table). The correction method is not limited to the method in which the difference chromaticity value is added and corrected as described above, and the coefficient as the correction strength is A, and “A × difference chromaticity value” is added to obtain the chromaticity value. (The value on the output side of the color conversion table) may be corrected. Here, the range of the correction strength coefficient A is, for example, 0 <A ≦ 2. When A = 1, it is equivalent to correcting the difference chromaticity value as it is. In order to prevent vibration when the feedback adjustment is repeated, it is preferable to set the correction strength coefficient A to a value slightly smaller than 1, for example, “0.75”. The correction strength coefficient A may be a fixed value determined in advance, or may be appropriately changed by the user.

  The lattice points to be corrected are the same as those described in the first embodiment (FIGS. 10 and 11).

  An example of a color conversion table for CM2 colors will be described. FIG. 14 shows correspondence data representing the correspondence between the document image signal (CM) and the chromaticity value (Lab). FIG. 14 shows correspondence data of a document image signal (CM), a target chromaticity value (target Lab), a printing chromaticity value (printing Lab), and a differential chromaticity value (difference Lab). FIG. 14 is obtained by adding “print Lab” and “difference Lab” to the corresponding data described in FIG. 10.

  The difference chromaticity value (difference Lab) shown in FIG. 14 is added to the chromaticity value (Lab value of the grid point) of the color conversion table of the original input profile to correct the chromaticity value.

That is, the original Lab values associated with grid points of _{P 1} in FIG. 11, the difference Lab = (+ 1, -1,0) by adding, modifying the Lab values.

Similarly, for the lattice points of P ₂₁ , P ₂₂ , P ₂₃ , and P ₂₄ , the Lab value is corrected by adding the difference Lab = (+ 1, −4, −2) to the original Lab value.

Similarly, for the lattice points of P ₃₁ , P ₃₂ and P ₃₄ , the Lab value is corrected by adding the difference Lab = (+ 1, −4, −2) to the original Lab value.

Similarly, for the lattice points P ₄₂ , P ₄₃ , and P ₄₄ , the Lab value is corrected by adding the difference Lab = (− 1, +3, −5) to the original Lab value.

For grid points P ₃₃ = P ₄₁ overlapping with ID = 3 and ID = 4, the average value of the difference Lab of ID = 3 and the difference Lab of ID = 4 is obtained, and the average value is used as the original Lab value. Add to correct the Lab value. In the case of FIG. 14, since the average value of the difference Lab with ID = 3 and the difference Lab with ID = 4 is (−0.5, 0, −1), this average value is represented by the lattice point P ₃₃ = P ₄₁ . Correct by adding to the Lab value.

For the grid points of P ₅₁ and P ₅₂ , the Lab value is corrected by adding the difference Lab = (− 1, 0, −2) to the original Lab value.

    In the above specific example, the Lab value is corrected by adding the difference Lab as it is, but as already described, the correction strength coefficient A is used to add and correct “A × difference Lab”. You may make it do. In this case, the overlapping grid points are corrected by adding the average value of “A × difference Lab”.

  If the chromaticity value of the grid point of the color conversion table is corrected by the method as described above, it is expected that the continuity (smoothness of change) of the color conversion table will deteriorate. For this reason, it is also preferable to perform a smoothing process on the corrected color conversion table. Further, the adjustment of the difference Lab using the correction strength coefficient A as the adjustment amount may be used together with the smoothing process.

[Example of how to create a color correction table]
Similar effects can be obtained in the form of a color correction table instead of the configuration in which the difference between the target chromaticity value and the printing chromaticity value is reflected in the color conversion table of the input profile as described above.

  FIG. 15 is a conceptual diagram when a color correction table is used. The color correction table 182 is a table that corrects chromaticity values between the color conversion table 166 of the input profile and the color conversion table 168 of the output profile in the second color conversion unit 80. The color correction table 182 is a color conversion table of the color correction profile 96 described with reference to FIG. Here, a Lab → Lab conversion table for converting an input Lab value into an output Lab value is exemplified as the color correction table 182. That is, the color correction table 182 serves to correct the output value of the color conversion table 166 (input color conversion table) of the input profile.

  Based on the correspondence data described in FIG. 14, the color correction table 182 can be created as follows.

  When the target Lab value that is the input Lab value in the color correction table 182 corresponds to the grid point, the Lab value (output Lab value) of the grid point corresponding to the target Lab value is expressed as [Target Lab + (Target Lab-Print Lab)].

  If the target Lab value does not correspond to the grid point, the Lab point (output Lab value) of the grid point surrounding the target Lab value is set to the value of [Target Lab + (Target Lab−Printing Lab)].

  Table values are set so that the input Lab value is equal to the output Lab value for grid points that are not subject to color correction.

  Regarding the method of creating the color correction table 182 described above, when the correction strength coefficient is A and the target Lab value serving as the input Lab value in the color correction table 182 corresponds to the grid point, the target Lab The Lab value (output Lab value) of the grid point corresponding to the value may be set as [Target Lab + A × (Target Lab−Print Lab)]. If the target Lab value does not correspond to the grid point, the Lab value (output Lab value) of the grid point surrounding the target Lab value is set to a value of [Target Lab + A × (Target Lab−Print Lab)]. You may do it. As already described, the range of the correction strength coefficient A is, for example, 0 <A ≦ 2. Preferably, the correction strength coefficient A is a value slightly smaller than 1. The correction strength coefficient A may be a fixed value determined in advance, or may be appropriately changed by the user.

  In FIG. 15, CMYK → Lab conversion by the color conversion table 166 of the input profile, Lab → Lab conversion by the color correction table 182, and Lab → CMYK conversion by the color conversion table 168 of the output profile are performed step by step. However, in actual calculation processing, these three color conversion tables (166, 182 and 168) can be integrated into a single color conversion table of CMYK → CMYK conversion. Using this integrated multi-dimensional (CMYK → CMYK) color conversion table, color conversion can be performed in a single process.

[Example of how to modify the color conversion table of the output profile]
As another method, the same effect can be realized by correcting the color conversion table 168 of the output profile.

  When correcting the color conversion table 168 of the output profile, the CMYK value of the grid point corresponding to the target Lab value is corrected so that the chromaticity value changes by the difference chromaticity value.

  Regarding the method of correcting the color conversion table 168 of the output profile exemplified above, the correction intensity coefficient is A, and the CMYK value of the grid point corresponding to the target Lab value is the chromaticity value corresponding to A × the difference chromaticity value. You may make it correct so that may change. As already described, the range of the correction strength coefficient A is, for example, 0 <A ≦ 2. Preferably, the correction strength coefficient A is a value slightly smaller than 1. The correction strength coefficient A may be a fixed value determined in advance, or may be appropriately changed by the user.

  As described above, the third color conversion table creation unit 102 in the second main configuration (see FIG. 5) determines the input color conversion table or the output color conversion table from the difference between the target chromaticity value and the print chromaticity value. Or a color correction table is created.

  In the second main configuration, the original image data 40 is again generated using the corrected input color conversion table, output color conversion table, or color correction table created by the third color conversion table creation unit 102. Perform color conversion and print.

  Thereby, it is expected that the color of the printed matter printed by the printing device 18 approaches the color of the target printed matter.

  In the second main configuration, the above-described series of procedures “second color conversion → printing → printed material reading / acquisition of chromaticity value / association of image and chromaticity value → correction of color conversion table (color correction table creation)” is performed. By repeatedly performing it, it is expected that the color of the printed matter is closer to the color of the target printed matter (target color).

[Combined use of the colorimeter 32]
Various error factors can be considered in the chromaticity values obtained by reading the target printed matter 42 or the printed matter 50 printed by the printing apparatus 18 with the image reading unit 30 such as a scanner. Error factors may include, for example, scanner reading errors, scanner profile errors, image signal and chromaticity value association errors, and color conversion table creation errors.

  Therefore, it is preferable to use a spectrocolorimeter (colorimeter 32) in combination in order to reduce the influence of such error factors and further increase the accuracy of color matching. Color matching accuracy can be improved by combining information acquired via the image reading unit 30 and information measured by the spectrocolorimeter.

[Color measurement method, color measurement value and image position association method]
Regarding the gradation part and the pattern part of the printed matter, it is physically difficult to obtain a colorimetric value corresponding to a desired image signal value with a spectrocolorimeter. The main reasons are that, firstly, the aperture of the spectrocolorimeter has a certain size, and secondly, it is difficult to precisely adjust the colorimetric position to a desired position. .

  In this regard, a colorimetric value for a desired image signal value can be easily obtained if it is a flat mesh part (a part where a constant image signal value is widened) having an area sufficiently larger than the aperture of the spectrocolorimeter. It is.

  In the present embodiment, there are the following methods as a method for obtaining the colorimetric value corresponding to the image signal value by the colorimeter 32.

  (1) In the first method, the original image data is analyzed, a flat mesh portion measurable by the colorimeter 32 is automatically specified, and a recommended colorimetric position is displayed on the display unit 34 (see FIG. 1). This is a method for causing the user to perform color measurement.

  In this case, in the document image data, a color with a larger number of pixels of the same color has a higher priority, and the candidates for the recommended colorimetric positions are displayed in order of priority from the top in the graphical user interface (GUI). You may make it arrange.

  (2) The second method is a method in which the image content (original image) of the original image data is displayed on the display unit 34, and the user selects a colorimetric position on the screen and performs colorimetry.

  It should be noted that any colorimeter that can automatically measure color by specifying a position can be instructed to perform automatic colorimetry by instructing the colorimeter.

  In the second method in which the user designates the color measurement position on the screen, when the user designates the gradation part or the picture part, the color measurement target image signal value is within a certain range in the image corresponding to the user designated position (for example, The colorimetric value can be obtained as an averaged colorimetric value within the aperture range by performing colorimetry at a specified position. is there.

  In this case, it is preferable to prompt the user to perform the color measurement a plurality of times at the user-specified position (including the vicinity thereof), and to obtain a color measurement value by averaging a plurality of color measurement results. That is, when the user manually adjusts the position of the colorimeter 32, a slight shift occurs in the colorimetric position. Therefore, a plurality of colorimetry is performed, and a plurality of colorimetry results are averaged. Thus, it is preferable to reduce the influence of the measurement error due to the positional deviation.

  FIG. 16 shows an example of a GUI when selecting a colorimetric position. A measurement position selection screen 200 as shown in FIG. 16 is displayed on the display unit 34 of the image editing apparatus 12 described with reference to FIG. The measurement position selection screen 200 includes an image display area 202, a measurement point display field 204, a measurement execution button 206, a measurement point addition button 210, an OK button 212, and a cancel button 214.

  The measurement position selection screen 200 displays the image file name of the image data corresponding to the printed matter to be measured and the model name of the measuring instrument connected to the system.

  In the image display area 202, the image content of the image data corresponding to the printed matter to be measured is displayed. In the illustrated image, an area indicated by “a” (a part surrounded by a frame line of reference numeral 221) and a region indicated by “b” (a part surrounded by a frame line of reference numeral 222) are analyzed in the original image data. The flat net portion recommended as the colorimetric position is shown.

  An identification code (ID) as a recommended colorimetric position is assigned to the flat mesh portion recommended as the colorimetric position, and frame lines 221 and 222 indicating the recommended colorimetric position on the image displayed in the image display area 202. Is overlaid. In FIG. 16, rectangular frame lines 221 and 222 are illustrated, but the shape of the frame lines 221 and 222 is not limited to a rectangle, and may be an arbitrary graphic shape such as another polygon or circle. .

  In addition, information on recommended colorimetric positions is displayed in the measurement point display field 204 in order of priority. ID = a indicates the recommended colorimetric position corresponding to the area surrounded by the frame line 221, and ID = b indicates the recommended colorimetric position corresponding to the area surrounded by the frame line 222.

  The measurement point display field 204 displays measurement point identification codes (ID) and information on CMYK values of the document image corresponding to each measurement point (colorimetric position).

  The measurement point addition button 210 is a GUI button that allows the user to freely set a measurement point (that is, a color measurement region) on the original image in addition to the recommended color measurement position (color measurement region). . When the measurement point addition button 210 is pressed, the user can manually add a measurement point (colorimetric region) on the document image. As a method for designating a desired measurement point, means for designating a position or region on an image from a pointing device or a touch panel of the input device 36 (see FIG. 1) can be adopted.

  Note that the expression “push” for the measurement point addition button 210 and other GUI buttons includes an operation of inputting a command corresponding to the button, such as clicking or touching.

  The measurement execution button 206 is a GUI button for instructing execution of color measurement by the colorimeter 32 (see FIG. 1). In this example, a measurement execution button 206 is provided for each measurement point candidate listed in the measurement point display field 204.

  When the measurement execution button 206 is pressed, color measurement by the colorimeter 32 is executed for the image position corresponding to the corresponding measurement point. When colorimetry is performed by the colorimeter 32 and a colorimetric value (Lab value in this example) is acquired from the colorimeter 32, the colorimetric result is displayed in the corresponding Lab value display cell 230 of the measurement point display field 204. The Lab value is displayed.

  The OK button 212 is a GUI button that gives a command to complete the measurement by the colorimeter 32. The cancel button 214 is a GUI button that gives a command to cancel processing or operation. By pressing the OK button 212, the measurement process by the colorimeter 32 is completed, and the measurement result is saved.

  In the above description, the case where the colorimeter 32 measures the color of a specific portion in the image of the target printed matter 42 or the printed matter 50 printed by the printing apparatus 18 has been described, but the measurement target by the colorimeter 32 is the target printed matter. 42 and the printed matter 50.

  In addition to the target printed matter 42 and the printed matter 50, when the target color is specified by another sample such as a color chip, the color chip may be measured instead of the target printed matter 42.

  In this way, combination data of an image signal (original image signal or read image signal) at a position subjected to colorimetry by the colorimeter 32 and a colorimetric value acquired by the colorimeter 32 is obtained. Two specific examples relating to the method of using the combination data will be described below.

[First example of colorimetric value utilization method]
As a first example of a method for using the colorimetric values obtained from the colorimeter 32, a method for directly reflecting the colorimetric values in the correspondence between the document image and the chromaticity values will be described.

FIG. 17 is a block diagram showing a configuration according to a first example of the colorimetric value utilization method. The configuration shown in FIG. 17 is a configuration in which a colorimeter 32, a chromaticity value replacement unit 74, and a color measurement target document image signal acquisition unit 240 are added to the first main configuration described in FIG. ing. In the configuration shown in FIG. 17, elements that are the same as or similar to the configuration described in FIG. 3 are assigned the same reference numerals, and descriptions thereof are omitted.

  The color measurement target document image signal acquisition unit 240 grasps the position on the document image corresponding to the color measurement position obtained by measuring the color of the printed matter using the colorimeter 32, and sets the color measurement position in the document image data 40. This is means for obtaining a document image signal value (referred to as “colorimetry target document image signal value”) at the corresponding image position.

  The function of the colorimetric target document image signal acquisition unit 240 is included in the colorimetric position association unit 70 described with reference to FIG. The color measurement position associating unit 70 provides means for providing the color measurement recommended position described in FIG. 16, a GUI that allows the user to set the color measurement position, and automatically performs color measurement for the specified color measurement position. Colorimetric means and the like can be included.

  The chromaticity value replacement unit 74 generates a “correspondence between original image signal and chromaticity value” generated by performing processing by the image association unit 62 and the first color conversion unit 64 on the read image data of the target printed matter 42. For the “related data”, a colorimetric value (Lab value in this case) acquired from the colorimeter 32 and a colorimetric object original image signal value (CMYK value) obtained from the colorimetric object original image signal acquisition unit 240 are obtained. Based on this, a replacement process is performed in which the chromaticity value data corresponding to the colorimetric object image signal value corresponding to the colorimetric position of the printed matter on the original image is replaced with the colorimetric value acquired by the colorimeter 32.

  Based on the “correspondence data between original image signal and chromaticity value” after the replacement process generated through the replacement process by the chromaticity value replacement unit 74, the second color conversion table creation unit 66A performs the second color conversion. A table 92A is created.

  The configurations of the colorimeter 32, the colorimetric target document image signal acquisition unit 240, and the chromaticity value replacement unit 74 described with reference to FIG. 17 are similarly added to the configuration illustrated in FIG. 4 and the configuration illustrated in FIG. Can do.

  FIG. 18 is a block diagram showing a configuration in which a function for replacing a chromaticity value with a colorimetric value is added to the second main configuration described in FIG.

  The configuration shown in FIG. 18 is a configuration in which a colorimeter 32, a chromaticity value replacement unit 74, and a color measurement target document image signal acquisition unit 240 are added to the second main configuration described in FIG. ing.

  In the case of the configuration illustrated in FIG. 18, the colorimeter 32 can execute color measurement on both the target printed material 42 and the printed material 50 printed by the printing apparatus 18.

  The chromaticity value replacement unit 74 obtains “correspondence data between the original image signal and the chromaticity value of the target printed material” obtained by reading the target printed material 42, and “original image signal and chromaticity of the printed material obtained by reading the printed material 50. Both chromaticity values of the “value correspondence data” can be replaced with colorimetric values obtained from the colorimeter 32.

  “Correspondence data of original image signal and chromaticity value of target printed matter” and “correspondence data of original image signal and chromaticity value of printed matter” after replacement processing generated through replacement processing by chromaticity value replacement unit 74 Based on the above, the third color conversion table creation unit 102 corrects the input color conversion table or the output color conversion table of the second color conversion unit 80, or creates a color correction table.

  In this way, the color conversion accuracy is further improved by directly reflecting the colorimetric value from the colorimeter 32 in the data of the correspondence between the image signal and the chromaticity value.

[Second example of colorimetric value utilization method]
As a second example of the method of using the colorimetric values obtained from the colorimeter 32, a method of selecting or correcting a scanner profile based on the colorimetric values will be described.

  The scanner used in the image reading unit 30 generally acquires an image signal (scanner image signal) acquired through a filter of RGB three primary colors. The spectral sensitivities of the RGB three primary color filters are different from the XYZ color matching functions of the spectrocolorimeter.

  The scanner profile associates a scanner image signal with a colorimetric value (a chromaticity value in a device-independent color space). The spectral sensitivity of the RGB three primary color filters in the scanner (that is, the spectral sensitivity of the scanner) is different from the XYZ color matching function of the spectrocolorimeter. Therefore, in the case of color materials and base materials having different spectral characteristics, the XYZ values (Lab values) acquired by the colorimeter 32 may be different even when the RGB signal values acquired by the scanner are the same. . In other words, the scanner profile depends on the color material and substrate of the printed material.

  Therefore, a plurality of scanner profiles for various color materials and base materials are prepared in advance in the database, and the most important for the colorimetric values in the actual printed matter from the relationship between the colorimetric reading image signal and the colorimetric values. A configuration in which a close scanner profile is selected is preferable.

  Further, the color conversion table of the scanner profile is corrected from the relationship between the colorimetric target read image signal and the colorimetric value, so that the chromaticity value obtained by the image reading unit 30 is close to the colorimetric value obtained from the actual printed matter. Such a configuration is also preferable.

  FIG. 19 shows a configuration example provided with means for selecting and correcting a scanner profile based on the colorimetric values. Here, a case where both the selection and correction of the scanner profile are performed using the colorimetric values obtained from the colorimeter 32 will be described, but an embodiment in which either the scanner profile selection or correction is performed is also possible. . That is, a mode in which only selection of a scanner profile is performed may be performed, or a mode in which only one scanner profile is prepared and only correction is performed adaptively may be employed.

  The configuration example of the image editing apparatus 12 illustrated in FIG. 19 is different from the first main configuration illustrated in FIG. 3 in that the colorimeter 32, the color measurement target read image signal acquisition unit 242, the color conversion table database 250, One color conversion table selection unit 252 and a first color conversion table correction unit 254 are added.

  The color measurement target read image signal acquisition unit 242 determines a position on the read image data corresponding to the color measurement position obtained by measuring the color of the printed matter using the colorimeter 32 based on the read image data obtained from the image reading unit 30. It is means for grasping and acquiring an image signal value (referred to as “colorimetric target read image signal value”) at an image position corresponding to a colorimetric position in the read image data.

  The function of the color measurement target read image signal acquisition unit 242 is included in the color measurement position association unit 70 described with reference to FIG. Note that the functions of the colorimetric object document image signal acquisition unit 240 described in FIG. 17 and the colorimetry object read image signal acquisition unit 242 in FIG. This is common in that an associated image signal (color measurement target image signal) is acquired. The color measurement target document image signal acquisition unit 240 described in FIG. 17 and the color measurement target read image signal acquisition unit 242 of FIG. 19 can be integrated as a color measurement target image signal acquisition unit.

  The color conversion table database 250 stores a plurality of scanner profiles for various combinations of color materials and base materials. The color conversion table database 250 can store scanner profiles that have been created or modified in the past in the present system. In the color conversion table database 250, for various combinations of color material types and base material types that can be used for printing by the printing device 18, read signals and chromaticity values from the image reading unit 30 for each combination are stored. A color conversion table representing the correspondence relationship is stored. The color conversion table database 250 corresponds to “a first color conversion table database in which a plurality of color conversion tables applicable as a first color conversion table are stored”.

  The first color conversion table selection unit 252 is based on the color measurement value obtained from the colorimeter 32 and the color measurement target read image signal value obtained from the color measurement target read image signal acquisition unit 242. A process of selecting an appropriate scanner profile from the database 250 is performed.

  The first color conversion table correction unit 254 compares the colorimetric values obtained from the colorimeter 32 and the colorimetric target read image signal acquisition unit with respect to the color conversion table of the scanner profile read from the color conversion table database 250. Based on the colorimetric object read image signal value obtained from 242, the table value is corrected. The first color conversion table correction unit 254 is included in the first profile correction unit 72 described with reference to FIG.

  The first color conversion table 68A obtained through at least one of the selection process by the first color conversion table selection unit 252 and the correction process by the first color conversion table correction unit 254 is the first color conversion. Applied to part 64.

[Example of how to select a scanner profile]
The first color conversion table selection unit 252 performs the following processing.

  The Lab value obtained by referring to the color conversion table (RGB → Lab conversion table) of the scanner profile from the color measurement target read image signal value (in this case, RGB value) corresponding to the colorimetric position, and the colorimeter 32 measures the Lab value. The color difference of Lab values (colorimetric values) obtained by coloration is calculated, and the average color difference, the maximum color difference, or both are calculated.

  Such a process is performed for all scanner profiles in the color conversion table database 250 prepared in advance, and the scanner profile that uses the scanner profile that minimizes the average color difference and the maximum color difference in the first color conversion unit 64. Select as a profile.

  The color conversion table of the scanner profile thus selected may be applied to the first color conversion unit 64 as it is, and the color conversion table of the scanner profile is further corrected by the first color conversion table correction unit 254, The corrected color conversion table may be applied to the first color conversion unit 64.

[First example of scanner profile correction method]
Next, a first example of a correction method in the first color conversion table correction unit 254 will be described.

  The first color conversion table correction unit 254 converts the color conversion table in the same manner as the color conversion table correction method described as [Example 2] regarding the second color conversion table creation unit 66A (see FIG. 3). It can be set as the structure correct | amended directly.

  In the above described [Embodiment 2], a desired color conversion table is obtained by correcting the chromaticity values of the grid points of the existing color conversion table using the correspondence data between the document image signal and the chromaticity values. Met.

  On the other hand, the first color conversion table correction unit 254 uses the correspondence data between the read image signal obtained from the image reading unit 30 and the colorimetric value, and the grid points in the color conversion table of the existing scanner profile. The color conversion table of the desired scanner profile is obtained by correcting the chromaticity value.

  That is, about the grid points around the read image signal where the colorimetric values exist, that is, about the grid points around the read image signal that can be measured by the colorimeter 32 in the flat mesh portion on the printed matter. The color conversion table can be corrected by replacing the chromaticity value with the measured value.

  As in the example described in [Embodiment 2], it is also preferable to further perform a smoothing process on the corrected color conversion table.

[Second example of scanner profile correction method]
Next, a second example of the correction method in the first color conversion table correction unit 254 will be described.

  The first color conversion table correction unit 254 determines the color reproduction model of the image reading unit 30 from the local relationship between the read image signal and the colorimetric value in which the correspondence between the read image signal and the colorimetric value is specified. It is possible to adopt a configuration that estimates and corrects the entire color conversion table of the existing scanner profile.

  For example, the following 3 × 3 matrix and RGB gamma (γ) values are assumed as the color reproduction model of the scanner used in the image reading unit 30. The 3 × 3 matrix is a matrix having XYZ values of RGB primary colors as components. The γ value represents the nonlinearity of RGB single color gradation.

  R, G, and B are device signal values (read image signal values) of the image reading unit 30, and are signal values obtained from the image reading unit 30 normalized to “0-1”.

  X, Y, and Z are colorimetric values corresponding to the read image signal values. The parameters of the color reproduction model are XYZ values (Xr, Yr, Zr) for R primary colors, XYZ values (Xg, Yg, Zg) for G primary colors, XYZ values (Xb, Yb, Zb) for B primary colors, and γ values for RGB ( γr, γg, γb), a total of twelve.

  Since the correct values of the colorimetric values X, Y, and Z with respect to the read image signal values (R, G, B) are obtained for each measurement point, three equations are obtained. Therefore, in order to obtain the color reproduction model of the image reading unit 30 corresponding to the current printed matter, it is sufficient to prepare four or more measurement points on the printed matter. By preparing four or more measurement points, the number of equations becomes twelve or more, and twelve unknown parameters can be obtained by simultaneously solving these equations. If there are 5 or more measurement points, the solution is optimized.

  Existing color conversion tables can also be applied to the above color reproduction model.

  That is, the XYZ values of the primary colors R, G, and B and the γ values of the RGB gradations may be acquired from the color conversion table.

  In this way, a scanner color reproduction model corresponding to the current printed matter and a scanner color reproduction model corresponding to the existing color conversion table are obtained.

  When the color reproduction model is obtained, the following correction is performed on each grid point (R, G, B) of the existing color conversion table.

Corrected color conversion table grid point XYZ value = existing color conversion table grid point XYZ value + (XYZ value of scanner color reproduction model for current printed matter−XYZ value of scanner color reproduction model from existing color conversion table)
Note that a new color conversion table may be created using a model corresponding to the estimated current printed matter. However, since the number of colorimetric points on the printed material is assumed to be small, rather than creating a color conversion table from 1 based on a small amount of information, the color material is based on the general color reproduction characteristics of the existing color conversion table. It can be expected that the accuracy is better when the minute deviation due to the difference in the base material and the model is estimated and corrected.

  19, as shown in FIG. 20, the colorimeter 32 and the colorimetric target read image signal acquisition unit 242 are also provided for the second main configuration described in FIG. 5, as in FIG. 19. A color conversion table database 250, a first color conversion table selection unit 252, and a first color conversion table correction unit 254 can be added.

  In the configuration shown in FIG. 20, when the color materials and base materials used in the target printed matter 42 and the printed matter 50 are different, color measurement is performed on each of the target printed matter 42 and the printed matter 50, and the target printed matter read image signal and A scanner profile for selecting a target printed matter read image is selected and / or corrected based on the relationship between the colorimetric values of the target printed matter 42, and a scanner for converting the printed matter read image based on the relationship between the printed matter read image signal and the colorimetric values of the printed matter 50. Preferably, the profile is selected and / or corrected.

  That is, different scanner profiles are used in the color conversion of the target printed material read image and the printed material read image in the first color conversion unit 64.

<Third example of colorimetric value usage method>
FIG. 21 is a block diagram illustrating a modification of the configuration described in FIG. In the configuration shown in FIG. 21, elements that are the same as or similar to the elements described in FIG. 17 are given the same reference numerals, and descriptions thereof are omitted.

  The configuration example shown in FIG. 21 includes a color conversion table correction unit 76 instead of the chromaticity value replacement unit 74 in FIG. In the case of the configuration example shown in FIG. 21, the second color conversion table creating unit 66 </ b> A generates “original image signal and chromaticity value generated by processing by the image association unit 62 and the first color conversion unit 64. Temporary color conversion table is temporarily created based on the “correspondence relationship data”. The color conversion table correction unit 76 is a provisional color conversion table created by the second color conversion table creation unit 66A, a colorimetric value (Lab value here) acquired from the colorimeter 32, and a colorimetry. Based on the colorimetric object image signal value (CMYK value) obtained from the object image signal acquisition unit 240, the chromaticity value in the provisional color conversion table is replaced with the colorimetric value acquired by the colorimeter 32. Perform correction processing. After the correction process by the color conversion table correction unit 76, the second color conversion table 92A is generated.

  According to the configuration example shown in FIG. 21, the colorimetry device directly modifies the profile, which is the color conversion table temporarily created by the second color conversion table creation unit 66A, with the colorimetric values of the colorimeter 32. The colorimetric value of 32 is reflected with high accuracy on the color conversion table.

  FIG. 22 is a block diagram illustrating a modification of the configuration described in FIG. In the configuration shown in FIG. 22, the same or similar elements as those of the configuration described in FIG. 18 are denoted by the same reference numerals, and the description thereof is omitted.

  In the configuration example shown in FIG. 22, a color conversion table correction unit 76 is provided instead of the chromaticity value replacement unit 74 in FIG. In the case of the configuration example shown in FIG. 22, the third color conversion table creating unit 102 generates “the original image signal and the chromaticity of the target printed matter generated through the processing by the image association unit 62 and the first color conversion unit 64. A temporary color conversion table is once created based on “value correspondence data” and “document image data and chromaticity value correspondence data of printed matter”. The color conversion table correction unit 76 includes a provisional color conversion table created by the third color conversion table creation unit 102, a colorimetric value (Lab value here) acquired from the colorimeter 32, and a colorimetric measurement. Correction that replaces the chromaticity value in the provisional color conversion table with the colorimetric value acquired by the colorimeter 32 based on the colorimetric target original image signal value (CMYK value) obtained from the target original image signal acquisition unit 240. Process. The color conversion table 77A is generated through correction processing by the color conversion table correction unit 76. The color conversion table 77A thus obtained is used in the second color conversion unit 80.

  According to the configuration example shown in FIG. 22, since the temporary color conversion table created by the third color conversion table creation unit 102 is directly corrected with the colorimetric values of the colorimeter 32, the colorimetry by the colorimeter 32 is performed. The color value is reflected on the color conversion table with high accuracy.

<Specific example of color extraction method after alignment>
Here, a specific example of the color extraction method after the alignment of the document image data and the read image data will be described.

  The image association unit 62 described with reference to FIG. 2 performs a process of extracting color information from each data (referred to as “color extraction process”) after aligning the document image data and the read image data.

  As color extraction processing after alignment, image signal values as color information are obtained in pixel units at corresponding positions in the original image data and read image data, that is, pixel by pixel. Of course, it is possible to employ a configuration in which color information is acquired from a unit region having an area larger than the area of the pixel, not limited to a pixel unit. The number of pixels constituting the unit region for color extraction can be set to an arbitrary number of 2 or more. Various designs are possible for the shape and size of the unit region for color extraction.

  At the time of color extraction, it is possible to set a focus area of the size of the unit area on the document image data and extract color information from the focus area that satisfies the extraction condition. Hereinafter, specific examples will be described.

  FIG. 23 is a flowchart illustrating an example of a color extraction method that is performed after the original image data and the read image data are aligned. FIG. 23 is a flowchart of steps that can be added between step S122 and step S124 in the flowchart described in FIG. After step S122 in FIG. 6, the process proceeds to step S202 in FIG.

  First, processing for setting a region of interest in document image data is performed (step S202). The region of interest is an image region of a specified size that is of interest as a calculation target for color extraction processing.

  The region of interest can be, for example, a square region with a side of 1 millimeter [mm] on the printed material. Various settings can be made for the size and shape of the region of interest. Here, in order to simplify the description, it is assumed that the shape of the region of interest is a square.

  The area of the region of interest is preferably larger than the area of one pixel of the read image data. The area of one pixel of the read image data is specified from the reading resolution of the image reading unit 30. The upper limit of the area of the region of interest is preferably equal to the area of the aperture of the colorimeter 32 or slightly larger than the area of the aperture.

  The setting of the region of interest includes designation of a position in the image. The position of the region of interest is sequentially moved on the document image data, and processing (steps S204 to S210) is performed for the region of interest at each position.

  In step S204, it is determined whether or not scanning by moving the region of interest has been completed for all areas in the document image data (step S204). If it is No determination in step S204, it will progress to step S206 and it will be determined whether an attention area | region satisfy | fills 1st extraction conditions. The process in step S206 corresponds to “a process for determining whether or not the region of interest satisfies the first extraction condition”.

  The first extraction condition preferably includes a condition that the color difference in the region of interest is equal to or less than a threshold value. In the case of this example, the first extraction condition satisfies both of the two condition elements that an edge is not included in the attention area of the image and that the color difference in the attention area is equal to or less than a threshold value. Request that.

  “No edge in the region of interest” corresponds to “no edge in the region of interest”. “The color difference in the region of interest is equal to or smaller than the threshold value” corresponds to “the color difference in the region of interest is equal to or smaller than the first extraction threshold value defined as the allowable range”.

  The edge means a portion where the shading (brightness) or color in the image changes abruptly. In general, contours and lines in an image, boundary portions of different colors, and the like correspond to edges because their shades and colors change abruptly.

  The first extraction condition corresponds to the definition of “uniform area”. That is, the first extraction condition is a condition for extracting a “uniform area” in which an edge is not included in the attention area of the image and the color difference in the attention area is equal to or less than a threshold value. . “Uniform area” means an area where the colors in the area are uniform. The term “uniform” is used not only in the case of being strictly constant but also in a meaning including an allowable variation and error.

  As the first extraction threshold value determined as the allowable range for the color difference within the region of interest, for example, the value of ΔCMYK value can be determined as the allowable range of CMYK value variation. In addition, the first extraction threshold value can be determined for each of C, M, Y, and K as ΔC value, ΔM value, ΔY value, and ΔK value as an allowable range of variation. .

  If the region of interest satisfies the first extraction condition, a Yes determination is made in step S206, and the process proceeds to step S208.

  In step S208, it is determined whether the region of interest satisfies the second extraction condition.

  The second extraction condition is that the read image data exists in the focus area in the read image data at the position corresponding to the focus area satisfying the first extraction condition, and the focus area in the read image data at the corresponding position It is required to satisfy both of the two condition elements that there is no image defect in the read image.

  Examples of the image defect include a scratch on a printed material to be read and dust attached at the time of reading. “Image defect does not exist” corresponds to “image defect does not exist”. As a specific example, this corresponds to “no scratches and garbage”, that is, “no scratches and garbage”. Scratches and dust that are image defects in the read image can be determined based on whether or not the variance value of luminance in the read image data is equal to or less than a threshold value. That is, if there are scratches or dust in the region of interest, the luminance dispersion value increases due to the influence. If the second extraction threshold value is defined as an allowable range for the luminance dispersion value, and the luminance dispersion value is less than or equal to the second extraction threshold value for the region of interest, there is no effect from scratches or dust. It is determined to be a “uniform area”. On the other hand, if the variance value of the luminance is larger than the second extraction threshold value, the presence of scratches or dust is suspected, and it is excluded from the extraction process as being excluded from the “uniform area”.

  In this example, a region of interest that satisfies the first extraction condition and satisfies the second extraction condition is extracted as a “uniform region”.

  If YES is determined in step S208, the process proceeds to step S210. In step S210, processing is performed to extract the image signal value in the region of interest determined to be a “uniform region” and the corresponding read image signal value. That is, a uniform (uniform) color is extracted with the size of the region of interest.

  After step S210, the process returns to step S202, the position of the region of interest is moved, and the processes of steps S202 to S210 are repeated. Further, in the case of No determination in step S206 or the case of No determination in step S208, the process returns to step S202 in any case.

  When the position of the region of interest is changed and scanning of all areas in the image is completed, a Yes determination is made in step S204, and the process proceeds to step S212.

  In step S212, data on the correspondence relationship between the image signal value extracted in step S210 and the read image signal value is generated. Assuming that the image signal value of the original is a CMYK value and the read image signal value is an RGB value, in step S212, the color information of the CMYK-RGB color information is obtained for a uniform region that satisfies the first extraction condition and the second extraction condition. Correspondence can be obtained. The process in step S212 corresponds to a “corresponding relationship color information extraction process”.

  After step S212, the process exits the flowchart of FIG. 23 and proceeds to step S124 described in FIG.

  Note that the second extraction condition determination process described in step S208 of FIG. 23 may be omitted. If the first extraction condition is satisfied in step S206 without considering the influence of scratches and dust (Yes determination in step S206), the process may proceed to step S210.

[Regarding the area of interest]
Regarding the setting of the region of interest, a plurality of types of regions of interest having different sizes can be determined. As the specified size of the region of interest, two or more different sizes with different areas are determined, and by setting the region of interest step by step in the area order (size order), each uniform region in the order of the area from within the image. It can also be extracted.

  For example, as the area size of the region of interest, three types of small, medium, and large are prepared, and each of the first size of the small area, the second size of the medium area, and the third size of the large area is sequentially illustrated in FIG. The color information extraction process can be performed in the attention area of each size by executing the flowchart of FIG.

  When the size of the region of interest is large, a color that occupies a relatively large area in the image is extracted. On the other hand, when the size of the region of interest is small, a color that occupies a relatively small area in the image is extracted. Since a color with a larger area in the image can be considered as a color having a higher importance level, a “weight” indicating the importance level of the color can be set according to the size of the region of interest. If the color extraction is performed in the order of the area of the region of interest, the weighting process for the extracted color is simple. The “weight” here is a value indicating the priority (importance) of color matching when creating a profile as a color conversion table. When creating a profile, a profile is created so that a color with a large weight is given priority and the estimation accuracy of the color is increased.

  Further, when setting the region of interest, if the alignment accuracy between the document image data and the read image data is low, the region of interest is preferably set to a large area. For example, when the alignment accuracy is low, the region of interest is set to a square with a side of 4 millimeters [mm], and only a uniform region within a relatively large region of interest is extracted.

  As a means for determining the accuracy of alignment, a configuration in which a document image and a read image as a result of the alignment process are displayed on the screen of the display unit 34 (see FIG. 1) can be employed.

  As a method of overlapping display, one of the original image and the read image can be converted into a transparent image and overlapped display can be performed. By such overlapping display, the user can visually confirm the alignment accuracy of the document image and the read image. When the alignment accuracy is low, the user can select a large area for the area of interest.

[Application of color extraction processing]
The color extraction method described in FIG. 23 can be applied as a color extraction method in the image association unit 62 having the configuration described in FIG. In addition, the color extraction method described in FIG. 23 can be added between step S132 and step S134 in the flowchart described in FIG. After step S132 in FIG. 6, it is possible to proceed to step S202 in FIG.

  The color extraction method described in FIG. 23 can also be applied as a color extraction processing method in the image association unit 62 having the configuration described in FIG. That is, as described with reference to FIG. 4, using the read chromaticity value image data obtained by performing color conversion processing by the first color conversion unit 64 on the read image data and converting the read image data into chromaticity values, The color extraction method similar to that in FIG. 23 can also be applied to the color extraction method after the alignment of the read chromaticity value image data. In this case, it is only necessary to replace the read image data with “read chromaticity value image data” and replace the RGB signal values with “chromaticity values” (Lab values).

[Description by specific printed material example]
Next, a specific example of the color extraction process described with reference to FIG. 23 will be described with reference to FIGS.

  FIG. 24 is a conceptual diagram showing an example of processing for setting the region of interest 262 in the document image data 260. In FIG. 24, the colors and shades of the image cannot be expressed due to the restrictions described in the drawing, but the actual image content has shades of various colors. The same applies to FIG.

  The document image data 260 corresponds to a specific example of the document image data 40 described with reference to FIG. In FIG. 24, a large size is drawn as the region of interest 262 for easy understanding. As an example of the size of the region of interest 262, a square with a side of 1 millimeter can be used. In FIG. 24, the initial position of the region of interest 262 is set at the upper left corner of the document image data 260. While sequentially moving the position of the region of interest 262 on the document image data 260 from this initial position, the processing of FIG. 23 is performed at each position, and the entire area of the document image data 260 is scanned.

  The arrows and broken lines in FIG. 24 conceptually show how the entire area is scanned by sequentially moving the position of the region of interest 262. Each position where the region of interest 262 is set is preferably a non-overlapping position where the regions of interest do not overlap.

  FIG. 25 shows an example of read image data obtained from the image reading unit 30 (see FIG. 2). The read image data 270 shown in FIG. 25 is read image data that has undergone the alignment process with the document image data 260 (see FIG. 24). The read image data 270 is associated with the original image data 260 by the image association unit 62 described with reference to FIG. The read image data 270 corresponds to a specific example of the “corresponding read image data 122” described with reference to FIG.

  In the read image data 270 of FIG. 25, black areas indicated by reference numerals 272, 273, and 274 indicate areas where no read image data exists. The read image data 270 in FIG. 25 is obtained by reading the printed material obliquely with respect to the image reading frame of the image reading unit 30 when the printed material is read by the image reading unit 30 (see FIG. 1). ing. The black coating regions 272, 273, and 274 correspond to regions that are out of the image reading frame due to the oblique arrangement of the printed matter.

  When the printed material is arranged obliquely with respect to the image reading frame of the image reading unit 30 or when the printed material is larger than the size of the image reading frame, an area where the read image data does not exist occurs.

  FIG. 26 shows an example of areas extracted from the document image data 260 shown in FIG. 24 as satisfying the first extraction condition and their colors. Each square cell shown in FIG. 26 corresponds to each set position of the region of interest 262 described in FIG. Through step S206 described in FIG. 23, a uniform color region is extracted in units of the area of the region of interest 262 as shown in FIG. In FIG. 26, the color extracted from the region of interest corresponds to the color of the document image data 260 in FIG. 24, but the color correspondence relationship cannot be expressed due to restrictions in the drawing.

  27 is extracted from the region in the read image data at a position corresponding to the region of interest extracted from the document image data 260 shown in FIG. 24 that satisfies the first extraction condition and satisfies the second extraction condition. This is an example of the area to be processed and its color. In FIG. 27, the color extracted from the area corresponding to the position of the target area corresponds to the color of the read image data 270 in FIG. Not done.

  The second extraction condition described in step S208 of FIG. 23 includes a condition that “corresponding read image data exists”. In FIG. 25, the read image data does not exist in the black painted areas indicated by reference numerals 272, 273, and 274. Therefore, in FIG. 27, for example, an area where read image data does not exist, such as an area indicated by reference numeral 276, does not satisfy the second extraction condition, and color extraction is not performed.

  As shown in FIGS. 24 to 27, the color information of the region of interest at the corresponding position is extracted from the document image data 260 and the read image data 270, and CMYK-RGB correspondence data is obtained.

[Additional conditions that can be added to the first extraction condition or the second extraction condition]
It is also possible to add an additional condition that “the periphery of the region of interest is the same color as the color of the region of interest” with respect to the first extraction condition or the second extraction condition described in FIG.

  FIG. 28 is an explanatory diagram drawn for explaining a region around the region of interest. FIG. 28 is an enlarged view of a part of the document image data. FIG. 28 shows a range of 7 × 7 regions of interest.

  A lattice region partitioned by the area size of the region of interest is called a “cell”. The condition that the area around the target area is the same color as the color of the target area is equivalent to the condition that there is no area (grid area) including an edge in the peripheral area.

  Here, it is assumed that the cell of “A” shown in the center of FIG. 28 and the region of 9 cells of 8 cells in contact with the periphery of the A cell have the same color. Further, it is assumed that the “peripheral region” is a range of eight surrounding cells adjacent to the region of interest. In this case, in the example of FIG. 28, when the cell indicated by “A” in the center becomes the “target region”, the neighboring eight cells adjacent to the periphery of A have the same color as A. Therefore, “A "Is extracted as a region that satisfies the condition that" the periphery of the region of interest is the same color as the color of the region of interest ".

  The method of determining the “peripheral area” is not limited to the example of FIG. 28, and only a part of the surrounding eight cells surrounding the cell A may be defined as the “peripheral area”. Further, a part or all of the 16 cells in contact with the outside may be added to the “peripheral region”.

[Example of weighting extracted color]
The following weight setting method can be adopted instead of or in combination with the configuration in which the weight is set according to the size of the region of interest.

  (Example 1) As described with reference to FIG. 28, when the area around the target area is the same color as the color of the target area, the weight of the color extracted from the target area is set to a large value. can do. In the example of FIG. 28, the weight of the color extracted from the center A is increased.

  (Example 2) A weight may be set according to the area occupied in the extracted color image. As the color occupies a larger area in the image, the weight can be increased.

  (Example 3) A weight may be set according to the appearance frequency of the color extracted according to the flowchart described in FIG. The higher the appearance frequency of the extracted color, the greater the weight. The appearance frequency can be expressed by the number of points of interest (points) extracted as the same color.

  (Example 4) A weight can be set according to the importance of color. The importance of the color can be set in advance. For example, a weight corresponding to the importance of each color can be determined for important colors such as a memory color, a special color, or a corporate color that are stored in advance as important colors.

  Any color can be designated as the memory color. For example, at least one color of pale orange, green, and blue can be designated. The user can specify an important color from an appropriate user interface, and can specify a weight for each important color. The user may directly specify the value of “weight”, or may specify “priority” correlated with “weight”. When specifying the priority, the correspondence between the weight and the priority is determined in advance, and the value of “weight” corresponding to the specified priority is specified. The important color may be registered in the database.

  (Example 5) The weight of the color measured by the colorimeter 32 may be increased. The color measured by the colorimeter 32 is considered to be an important color, and the obtained colorimetric value is highly reliable.

  (Example 6) As an example of reducing the weight, it is conceivable to reduce the weight of a color in a busy image area. With regard to a method for determining whether or not the image is a “busy image region”, for example, when an edge is included in an adjacent unit region, it can be determined that the image region is a busy image region.

  (Example 7) As another example of reducing the weight, it is conceivable to reduce the weight of the shadow area of the image density. In the shadow area, the reading accuracy of the scanner is generally low. That is, the gradation of the shadow area is apt to be lost in the read image. When the gradation is crushed, it means that the gradation cannot be sufficiently reproduced. Therefore, the color conversion accuracy can be improved by adopting a configuration in which the weight extracted from the shadow area is reduced.

  The “shadow region” can be specified based on the characteristics of the image reading unit 30 to be used. That is, it is possible to define a shadow region where the gradation is crushed according to the characteristics of the image reading unit 30 to be used.

  Further, since the accuracy of the read image signal in the shadow area is low, a condition that the color of the shadow area is not extracted may be added as an additional condition to the first extraction condition or the second extraction condition. Alternatively, it is possible to adopt a process of excluding the color extracted from the shadow area from the extraction result.

  (Example 8) As another example of reducing the weight, the weight of the color extracted from the area with low scanner reading reliability may be reduced, or the color may not be extracted from the area with low scanner reading reliability. . “A region where the scanner reading reliability is low” means a region where the accuracy of the read image signal is low. Specifically, the low-reliability region is, for example, a region having a width of about 1 centimeter [cm] to several centimeters [cm] around four sides of the scanning surface of the scanner used in the image reading unit 30. Point to.

FIG. 29 is an explanatory diagram illustrating a specific example of an area where reading reliability of the scanner is low. The outermost edge of the quadrangle indicated by reference numeral 278 in FIG. 29 represents the outer edge of the scan surface of the scanner, and the dimensions d ₁ , d ₂ , d ₃ , and d are respectively inward from the outer edges of the four sides around the scan surface. A region 279 having a width of ₄ is a “reliable region”. In the simplest example, the low-reliability region 279 is a region having a constant width on the four sides around the scan surface, that is, d ₁ = d ₂ = d ₃ = d ₄ . As another example, the width of the region along the vertical side in FIG. 29 and the width of the region along the horizontal side in FIG. 29 may be changed. That is, d ₁ and d ₃ which are the widths of the regions along the sides in the vertical direction have the same value (d ₁ = d ₃ ), and d ₂ and d ₄ which are the widths of the regions along the sides in the horizontal direction. Can be the same value (d ₂ = d ₄ ), and the width of the region along the vertical side and the width of the region along the horizontal side can be different from each other (d ₁ ≠ d ₂ ).

Since the low-reliability area varies depending on the scanner model, the dimensions d ₁ , d ₂ , d ₃ , and d ₄ that define the width of the area 279 may be appropriately set according to the performance of the scanner.

[How to reflect weights]
Next, an example of a method of reflecting “weight” when creating the color conversion table will be described. As described with reference to FIGS. 10 and 11, there are cases in which grid points are used when creating a color conversion table from the correspondence (CMYK-Lab) between a document image and a read chromaticity value. “Lattice points are in contact with each other” means, for example, a case where a plurality of chromaticity values correspond to the same lattice point in ID = 3 and ID = 4 in FIG. In the embodiment described with reference to FIGS. 10 and 11, when a plurality of chromaticity values correspond to one grid point, the chromaticity value of the grid point is a simple average of the plurality of chromaticity values. Even if there is an important color in the pattern, it is reflected as a simple average value in the color conversion table. That is, it is not distinguished whether it is an important color.

  Therefore, when creating (correcting) the color conversion table, the “important colors” are taken into account, and “weights” corresponding to the importance are set for the colors extracted by the color extraction process. A configuration in which “weight” is reflected when the Lab value of the conversion table is set or corrected can be adopted.

  FIG. 30 shows an example in which “weight” is further reflected in the example described with reference to FIGS. 10 and 11. In the case of a simple average Lab value of ID = 3 and ID = 4, Lab = (7.15, 2.5, −23).

On the other hand, when the weighted average Lab value of ID = 3 and ID = 4 is calculated using the weight setting shown in FIG. 30, the weighted average Lab = (w ₃ × Lab ₃ + w ₄ × Lab ₄ ) / (W ₃ + w ₄ ) = (7.11, 7.8, −20.5). w ₃ represents a weighting factor of ID = 3, and Lab ₃ represents a Lab value of ID = 3. w ₄ represents a weighting factor of ID = 4, and Lab ₄ represents a Lab value of ID = 4.

  The weighted average Lab = (7.11, 7.8, −20.5) has priority over the Lab value of ID = 3 compared to the simple average Lab = (7.15, 2.5, −23). Has been.

  Similarly, when the color conversion table of the input profile is corrected using the difference Lab described with reference to FIG. 14, the weighted average Lab value of the difference can be used.

  FIG. 31 shows an example in which “weight” is further reflected in the example described in FIG. Based on the difference Labs of ID = 3 and ID = 4, when the simple average difference Lab value, which is a simple average value thereof, is calculated, the simple average difference Lab value = (− 0.5, 0, -1).

On the other hand, when the weighted average difference Lab value, which is the weighted average value, is calculated based on the difference Lab of ID = 3 and ID = 4 using the weight setting shown in FIG. Average difference Lab = (w ₃ × ΔLab ₃ + w ₄ × ΔLab ₄ ) / (w ₃ + w ₄ ) = (− 0.1, −2.5, 2.3). w ₃ represents a weighting factor of ID = 3, and ΔLab ₃ represents a differential Lab value of ID = 3. w ₄ represents a weighting factor of ID = 4, and ΔLab ₄ represents a differential Lab value of ID = 4.

  The weighted average difference Lab = (− 0.1, −2.5, 2.3) is different from the simple average difference Lab = (− 0.5, 0, −1) as the difference Lab with ID = 3. Is prioritized.

[About white point extraction]
When the target printed matter 42 or the printed matter 50 is read by the image reading unit 30, the unprinted blank area of the read image may be colored due to the influence of surrounding colors in the printed image. For this reason, it is preferable to extract the white color of a specific area that is not adjacent to the surrounding color as “paper white”. The paper white information extracted from the specific area is used for the white point (wtpt) which is the tag information of the profile.

  As a method of acquiring white point information from an area where no color is adjacent to the surrounding area, as in the case of the weighting of the attention area described with reference to FIG. 28, adjacent cells (grid areas) having the same size as the attention area are white. The value of the center cell “A” in the case can be used as the white point.

  However, it is preferable that the region of interest when the white point is extracted is sufficiently large compared to the region of interest used for the color extraction processing and the weighting processing described with reference to FIGS. The size of the region of interest used for the color extraction processing and weighting processing described with reference to FIGS. 23 to 31 is approximately several millimeters [mm] on one side, whereas the size of the region of interest used for white point extraction is It is generally preferable that one side has a size of several centimeters [cm].

  As another method of acquiring white point information from an area where no color is adjacent to the surrounding area, the white area having the largest area or the white having the largest peripheral length among a plurality of white areas included in the document image data The average value of the lattice area close to the center of gravity of the area can be used as the white point. The “lattice area close to the center of gravity” can be the lattice area closest to the center of gravity.

  A method of obtaining the center of gravity of the white area will be described with reference to FIG. In FIG. 32, a range of 7 × 7 lattice regions (pixels) is shown, and it is assumed that a white region is a range of 5 × 5 lattice regions (pixels).

When the white area is composed of only n pixels in total, if the pixel position of each white pixel is represented by (X _i , Y _i ), the barycentric position of the white area can be obtained by the following equation.

  As another example of the white point extraction method, the following method may be employed.

<Other example 1>
As a countermeasure when there is no paper white equivalent on the entire surface of the printed material to be scanned, paper white colorimetric values for each representative paper category or individual paper brand are stored in advance or measured in advance. It is possible to adopt a configuration in which the database is colored and stored, and the user selects the paper white color measurement value of the same paper category or the same paper brand as the target printed matter. Typical paper categories include gloss coated paper, matte coated paper, and high quality paper, for example. Paper white colorimetric values can be determined in advance for each of the plurality of paper categories.

<Other example 2>
When a paper white portion exists in the printed material, the color of the paper white can be measured from the printed material. In other words, the paper white colorimetric value may be acquired by measuring the paper white part of the printed material with the colorimeter 32. Alternatively, if the same paper as the printed material is at hand, the paper white colorimetric value may be obtained by measuring the paper.

<Other example 3>
A configuration may be adopted in which paper white is automatically extracted from the entire read image (not the specific region where no color is adjacent to the periphery). For example, a read image signal value of a registered read image corresponding to all pixels or a region of interest that is (C, M, Y, K) = (0, 0, 0, 0) on a document image is extracted. The median value for each channel of the extracted read image signal value is adopted as the paper white information.

  When the read image signal value is an RGB value, a median value for each channel is obtained for each channel of R / G / B. Further, if the RGB value is already converted into the Lab value by the scanner profile as the read image signal value, the median value for each channel is obtained for each channel of L / a / b. The median value for each channel of the read image signal value obtained in this way can be adopted as the paper white information. Instead of the “median value” for each channel, the “average value” for each channel may be used.

  An XYZ value of paper white is used for the white point “wtpt” that is tag information of the profile. That is, the paper white information or the paper white colorimetric value acquired as described above is used after being converted into an XYZ value.

[Feedback Adjustment by Third Color Conversion Table Creation Unit 102]
The third color conversion table creation unit 102 described with reference to FIG. 5 creates CMYK-Lab correspondence data created from the original image data 40 and the read image of the target printed matter 42 (this is referred to as “first CMYK-Lab data”). ) And the CMYK-Lab correspondence data (referred to as “second CMYK-Lab data”) created from the read image of the actual printed matter 50 and the original image data 40, the second color conversion. It plays a role of correcting the color conversion table in the unit 80. Such correction processing is called “feedback adjustment”.

  In the case of the configuration described with reference to FIG. 5, the process for creating the first CMYK-Lab data and the process for creating the second CMYK-Lab data are performed independently, and color extraction processing is performed in each process. Are also implemented independently. Therefore, the first CMYK-Lab data may not necessarily correspond to the second CMYK-Lab data.

  Therefore, a process for confirming whether or not the first CMYK-Lab data and the second CMYK-Lab data correspond to each other is added, and only the data having the same CMYK value is used for feedback adjustment. A form to be used is also preferable.

  That is, of the CMYK-Lab extracted data group extracted in the creation process of the first CMYK-Lab data and the CMYK-Lab extracted data group extracted in the process of creating the second CMYK-Lab data, the CMYK value is A configuration in which “extracted data association processing” for extracting only matching data can be performed.

  The extracted data association processing unit as a processing unit that performs the extracted data association processing is between the first color conversion unit 64 and the third color conversion table creation unit 102 shown in FIG. 5, that is, the first color. It can be provided after the conversion unit 64 and before the third color conversion table creation unit 102. Alternatively, the extracted data association processing unit can be mounted as a part of the function of the third color conversion table creation unit 102.

  The process of the extracted data association process can be added as a pre-process of step S146 in FIG.

[How to reduce the computational load of alignment]
A large-size image and a high-resolution image require a large calculation load and a large-capacity memory area when performing alignment processing. Therefore, in order to reduce the calculation load, when performing the alignment process between the document image and the read image, the alignment process is performed in two processes, that is, the alignment process using the reduced image and the alignment process using the cut-out image. A configuration can be employed. The reduced image can be generated by thinning the original image data at a certain rate. The cutout image is a partial image obtained by cutting out a part of the original image.

  Since the alignment processing using the reduced image reduces the alignment accuracy, high-precision alignment is performed using the cut-out image that is a partial image of the original image after the alignment processing using the reduced image. By performing such stepwise alignment processing, the calculation load can be reduced.

  Alternatively, the original image is divided into a plurality of image regions, and each divided image is subjected to alignment processing and color extraction processing, and the results obtained for each divided image are integrated to obtain an image. A configuration in which the entire information is obtained is also possible.

[Response to surface processing]
For example, document image data for package printing used for packaging, containers, etc. includes a color data layer indicating the image content for printing, a cut line layer indicating the cut line after printing, and the contents of the surface processing of the printing surface. And a surface processed layer. As an example, in the ai format of Adobe illustrator (registered trademark) of Adobe Systems Inc., a color data layer, a cut line layer, and a surface processed layer are held as one layer in one file.

  The surface processing includes processing for forming a protective film on the printing surface by applying clear ink and / or varnish. Even if the CMYK values specified in the color data layer are the same, different colors appear depending on the presence or absence of surface processing. That is, even when reading is performed by the image reading unit 30 such as a scanner, different RGB values are obtained depending on the presence or absence of surface processing.

  Therefore, when obtaining color information from the read image of the target printed matter 42 or the printed matter 50, it is preferable to perform color extraction using information relating to surface processing.

  The information regarding the surface processing includes at least information for specifying the presence or absence of the surface processing. Color extraction is performed using either information of “with surface processing” or information of “without surface processing”.

  Specifically, the following measures can be taken.

  [1] When the entire printing surface is processed, the color data layer of the document image data can be used as it is.

  [2] When the printing surface is partially surface processed, the following two ways can be taken.

  [2-1] Color extraction is performed using color data in an area where there is no surface processing. That is, color extraction is performed using color data obtained by excluding the overlapping region between the surface processed layer and the color data layer from the color data layer.

  [2-2] Color extraction is performed using color data of a region having surface processing. That is, color extraction is performed using the color data of the overlapping area between the color data layer and the surface processed layer.

  In both cases [2-1] and [2-2] described above, the alignment processing of the original image data and the read image data is performed using the entire color data layer.

  FIG. 33 is a schematic diagram showing an example of document image data for package printing. FIG. 33A is a diagram showing an example of data in the color data layer, and FIG. 33B is a diagram showing an example of data in the surface processed layer. FIG. 33C is a diagram showing a state in which the color data layer and the surface processed layer are overlaid.

  Here, the description of the cut line layer is omitted for the sake of simplicity. Note that FIG. 33C can be interpreted as an overlay of the mask of the surface processing layer on the color data, and thus FIG. 33C is referred to as “color data layer after max”.

  In FIG. 33B, a blacked area (reference numeral 280) filled in black indicates an area where surface processing is performed (corresponding to “surface processing area having surface processing”), and in this example, clear processing as surface processing is performed. An area to which ink is applied is shown. In FIG. 33B, a non-black painted region (reference numeral 282) that is not painted black indicates a region where surface processing is not performed (corresponding to a “non-surface processed region without surface processing”). A region (non-applied region) to which clear ink as processing is not applied is shown.

  FIG. 34 is a flowchart of color extraction processing in which the presence or absence of surface processing is added to the color extraction conditions. In the flowchart shown in FIG. 34, steps that are the same as or similar to the steps described in the flowchart described in FIG. 23 are given the same step numbers, and descriptions thereof are omitted. Instead of the color extraction process described with reference to FIG. 23, a color extraction process shown in FIG. 34 can be employed.

  In the color extraction process flowchart shown in FIG. 34, a process step (step S207) for determining whether or not the third extraction condition is satisfied is added between step S206 and step S208 described in FIG. .

  The third extraction condition is the following two condition settings (condition setting 1 and condition setting 2) depending on whether the color is extracted from the area without surface processing or the color is extracted from the area with surface processing. Is possible.

  That is, as the condition setting 1 of the third extraction condition, a condition “being a non-surface processed region without surface processing” can be determined. Further, as the condition setting 2 of the third extraction condition, a condition that “the surface processing region has surface processing” can be set.

  Condition setting 1 and condition setting 2 are set by exclusive selection. The selection of whether to adopt condition setting 1 or condition setting 2 can be configured to be specified by the user from the user interface. The selection of whether to use condition setting 1 or condition setting 2 is performed by analyzing the document image data, and comparing the area of color data including surface processing and the area of color data not including surface processing. Of these, the automatic selection process of selecting condition setting 1 or condition setting 2 so as to extract colors from the larger area can be adopted. The function of the automatic selection process can be installed as a function of the image processing unit 24 and / or the control unit 26 described with reference to FIG.

  When the third extraction condition is set to condition setting 1, an area without surface processing is a color extraction target. In the example of FIG. 33C, an area (non-black area 282) other than the black area 280 is a color extraction target.

  On the other hand, when the third extraction condition is set in the condition setting 2, an area where the surface processing is performed becomes a color extraction target. In the example of FIG. 33C, the black area 280 is a color extraction target.

  According to the flowchart shown in FIG. 34, color information is acquired from a region of interest that satisfies all of the first extraction condition, the third extraction condition, and the second extraction condition.

  A form in which the process of step S208 in the flowchart of FIG. 34 is omitted is also possible.

[When using a camera for the image reader]
When the camera is used for image reading, unevenness in the read image may occur due to unevenness of light hitting the printed matter. The light that strikes the printed material can be ambient light, illumination light, or a combination thereof. In order to cope with the problem that unevenness in the read image acquired by the camera may occur due to unevenness of light hitting the printed material in this way, when the camera is used for the image reading unit 30 (see FIG. 1), shading is performed. It is also preferable to perform correction together.

  A photographed image obtained by photographing with a camera corresponds to a “read image”. The term “photographing” is synonymous with “imaging”. The camera has a two-dimensional image sensor as an image sensor, converts a captured optical image into electronic image data, and generates captured image data as a color image representing the captured image. The specific form of the camera is not particularly limited. The camera may be a single-plate imaging device in which R, G, and B color filters are arranged in a mosaic pattern corresponding to each photosensitive pixel on the light receiving surface of the two-dimensional image sensor. For a color separation optical system that divides into G and B color components and each of the R, G, and B channels, a three-plate type imaging device that includes a two-dimensional image sensor for each channel may be used.

  As an example of shading correction, for example, the following correction method can be employed. The shading correction method is not limited to the method exemplified below, and other known shading correction methods may be used.

  An example of the shading correction method includes a step of preparing shading data and a step of performing shading correction using the shading data.

(1) Shading data preparation process In the shading data preparation process, first, an unprinted paper is placed at the “position where the object is to be placed”, which is the position where the object is placed when the printed object is photographed with a camera. Shoot unprinted paper with the camera. From the unprinted paper photographed image data, which is image data obtained by photographing the unprinted paper with the camera, the maximum luminance value Lmax in the unprinted paper photographed image data is obtained. Then, the shading data SHD (x, y) is obtained by the following equation.

SHD (x, y) = Lmax / L (x, y)
Here, x and y represent the position of the pixel, and L (x, y) represents the luminance value of the pixel at the position (x, y).

(2) Shading correction implementation step In the shading correction step, shading data SHD (x, y) is applied to camera-captured image data, which is image data obtained by photographing a printed matter with a camera, and shading is performed according to the following equation. Make corrections.

Dout (x, y) = SHD (x, y) × Din (x, y)
Here, Din (x, y) is input image data and represents camera-captured image data obtained by photographing a printed matter with a camera.

  Dout (x, y) is output image data for shading correction, and represents image data after shading correction for camera-captured image data.

  A function for generating shading data from unprinted paper photographed image data and a function for performing shading correction of camera photographed image data using the shading data can be installed in the image processing unit 24 (see FIG. 1). That is, the image processing unit 24 can include a shading data generation unit and a shading correction unit. The shading data generation function and the shading correction function can also be installed in an image processing circuit inside the camera.

  In the case of a scanner, since shading correction is generally performed on the main body side of the scanner, it is considered unnecessary to separately perform shading correction on image data obtained by scanning.

[About using an inline sensor in the image reading unit]
FIG. 35 is a block diagram showing the configuration of a printing system according to another embodiment of the present invention. In the configuration of FIG. 35, the same or similar elements as those described with reference to FIG.

  A printing system 310 illustrated in FIG. 35 includes an image reading unit 30A as a first image reading unit that reads the target printed matter 42. The image reading unit 30A has a configuration equivalent to that of the image reading unit 30 described in FIG. 1. The image reading unit 30A includes a scanner separate from the printing device 18 (for example, a so-called off-line scanner such as a flatbed scanner). Off-line scanner) or a camera.

  In addition, the printing apparatus 18 in the printing system 310 of FIG. 35 includes an inline sensor 30B as a second image reading unit that reads the printed matter 50. The in-line sensor 30 </ b> B functioning as the second image reading unit is a built-in printer type image reading device incorporated in the printing device 18. For example, the printing apparatus 18 has a configuration in which a line sensor, which is an image reading image pickup unit, is installed in a paper conveyance path, and reads a printed image by the line sensor while conveying a printed matter after image formation. The inline sensor 30 </ b> B of this example is a line sensor for image reading installed in the paper conveyance path of the printing apparatus 18. That is, the in-line sensor 30B has a photoelectric conversion element array (read pixel array) that can read an image corresponding to the paper width on the paper in a paper width direction orthogonal to the paper transport direction at a time (by one paper feed). Installed in the paper transport path. The term “inline sensor” is sometimes called “inline scanner”.

  As the inline sensor 30B, for example, an image pickup device capable of color separation is used, such as a 3CCD color line sensor in which CCD (charge-coupled device) line sensors of RGB color channels are arranged. By using such a color imaging device, color information can be read from the printed matter 50 of the printing apparatus 18.

  While the printed matter 50 printed by the printing unit 16 of the printing apparatus 18 is conveyed in one direction, the image on the printed matter 50 is read by the inline sensor 30B and converted into an image signal. Thus, electronic image data of the read image read by the inline sensor 30B is generated.

  When the inline sensor 30B is built in the printing apparatus 18, the inline sensor 30B of the printing apparatus 18 can be used for reading the printed matter 50 printed by the printing apparatus 18. In this case, in order to convert the RGB signal values acquired by the inline sensor 30B into device-independent signal values (for example, Lab values), it is necessary to prepare a profile of the inline sensor 30B separately. Information acquired by the inline sensor 30B is sent to the image processing unit 24.

  FIG. 36 is a block diagram instead of FIG. In the case of the printing system 310 described with reference to FIG. 35, a block diagram in place of FIG. 5 is FIG. 36, the same reference numerals are given to the same or similar components as those described in FIG. 5, and the description thereof is omitted.

  As shown in FIG. 36, the target printed matter 42 is read by the image reading unit 30A. On the other hand, the printed matter 50 printed by the printing device 18 is read by the inline sensor 30B. The RGB value of the read image obtained from the inline sensor 30B is converted from the RGB value to the Lab value by the first color conversion unit 64 using the first color conversion table 68B that is the profile of the inline sensor 30B. . Other configurations are the same as the example described in FIG.

  As shown in FIGS. 35 and 36, it is also possible to use different image reading apparatuses for reading the target printed matter 42 and the printed matter 50 of the printing apparatus 18, respectively. That is, it can be understood that the combination of the image reading unit 30 </ b> A that reads the target printed material 42 and the inline sensor 30 </ b> B that reads the printed material 50 of the printing device 18 corresponds to an “image reading unit” as a whole.

  Similarly to FIG. 36, the image reading unit 30 having the configuration described with reference to FIGS. 18, 20, and 22 may employ a combination of the image reading unit 30 </ b> A that reads the target print 42 and the inline sensor 30 </ b> B that reads the print 50. it can.

  Further, the second image reading unit used for reading the printed matter 50 of the printing apparatus 18 is not limited to the inline sensor 30B, and an offline scanner or a camera is used similarly to the first image reading unit used for reading the target printed matter 42. You can also. That is, the first image reading unit used for reading the target printed material 42 and the second image reading unit used for reading the printed material of the printing device 18 may have different device configurations, respectively. A single apparatus configuration may be used for both the image reading unit and the second image reading unit.

<Regarding a program that causes a computer to function as a color conversion table creation device>
As the color conversion table creation device described in the above-described embodiment, a program for causing a computer to function is a CD-ROM (Compact Disc read-only memory), a magnetic disk, or other computer-readable medium (non-transitory information storage as a tangible object) Medium) and the program can be provided through the information storage medium. Instead of providing the program by storing the program in such an information storage medium, it is also possible to provide the program signal as a download service using a communication network such as the Internet.

  Further, by incorporating this program into a computer, each function of the color conversion table creation device can be realized by the computer, and the color conversion table creation and color conversion processing described in the above embodiment can be performed. it can.

<Modification of the embodiment>
Configuration examples related to the first main configuration described in FIGS. 3, 4, 17, 19, and 21, and the additional configuration thereof, and FIGS. 5, 13, 18, 10, 22, and 36. The second main configuration and the configuration example related to the additional configuration can be appropriately combined.

<Advantages of Embodiment>
(1) According to the first main configuration, the target printed matter 42 is read by the image reading unit 30 to acquire the chromaticity value, and the target profile color conversion table (second color conversion table 92A) is obtained from the target printed matter 42. Can be created. That is, the target profile color conversion table can be created based on the original image data 40 and the read image data of the target print 42 without performing the printing of the print 50 and the reading operation of the print 50.

  According to the first main configuration, when the target profile is created, it does not take time and labor for printing by the printing device 18 and reading the printed matter.

  (2) According to the second main configuration, the chromaticity value of the target printed matter obtained by reading the target printed matter 42 with the image reading unit 30 and the printed matter obtained by color conversion using the temporary input color conversion table are printed. Based on the chromaticity value of the printed matter read by the image reading unit 30, the provisional input color conversion table can be corrected, the output color conversion table can be corrected, or the color correction table can be created. Thereby, the color conversion table applied to the second color conversion unit 80 can be made more appropriate, and the accuracy of color conversion can be improved.

  Furthermore, by repeating this process, the color of the printed material can be made closer to the color of the target printed material 42.

  In addition, according to the second main configuration illustrated in FIG. 36, color conversion is performed using the chromaticity value of the target printed matter obtained by reading the target printed matter 42 with the image reading unit 30A and the provisional input color conversion table. Based on the chromaticity value of the printed matter obtained by reading the printed matter with the inline sensor 30B, the provisional input color conversion table can be corrected, the output color conversion table can be corrected, or the color correction table can be created. . Thereby, the color conversion table applied to the second color conversion unit 80 can be made more appropriate, and the accuracy of color conversion can be improved.

  Furthermore, by repeating this process, the color of the printed material can be made closer to the color of the target printed material 42.

  (3) By using the second color conversion table 92A created by the first main configuration as the first input color conversion table in the second main configuration, the accuracy of color reproduction in the first printing is optimized. , Color convergence will be faster.

  (4) According to the present embodiment, a conventional method for creating a color conversion table representing a multidimensional correspondence between chromaticity values corresponding to the document image data 40 and matching the colors of the target printed matter and the printed matter. Compared to the above, the degree of freedom of color correction is high, and more accurate color correction (color matching) is possible. According to the present embodiment, sufficient color matching accuracy can be obtained even when the color reproduction characteristics of the printing machine that outputs the target printed matter and the printing device 18 used for printing the printed matter 50 are greatly different.

  (5) By adopting the image association unit 62 including the document corresponding image extraction unit 130 described in FIG. 9, color matching is performed even when the document image data 40 and the print image of the target print 42 do not correspond one-to-one. Can be implemented.

  (6) By adopting a configuration in which the colorimeter 32 is used in combination, an error in measurement of chromaticity values acquired via the image reading unit 30 can be reduced, and color matching accuracy can be improved.

  (7) According to this embodiment, an appropriate color conversion table can be created even when a color reproduction target is specified by an actual print (target print), and color management using an ICC profile is possible. It becomes. In addition, the color matching process for the target printed matter can be made efficient.

  In the embodiment of the present invention described above, the configuration requirements can be appropriately changed, added, and deleted without departing from the spirit of the present invention. The present invention is not limited to the embodiments described above, and many modifications can be made by those having ordinary knowledge in the field within the technical idea of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Printing system, 12 ... Image editing apparatus, 18 ... Printing apparatus, 20 ... Image data input part, 24 ... Image processing part, 26 ... Control part, 30 ... Image reading part, 30A ... Image reading part, 30B ... Inline sensor 32 ... Colorimeter, 34 ... Display unit, 36 ... Input device, 40 ... Original image data, 42 ... Target printed matter, 50 ... Printed matter, 62 ... Image association unit, 64 ... First color conversion unit, 66 ... Target profile creation unit, 66A ... second color conversion table creation unit, 68A, 68B ... first color conversion table, 70 ... colorimetric position association unit, 72 ... first profile correction unit, 74 ... chromaticity value Replacement unit 80 ... second color conversion unit 120 ... read image data 130 ... document corresponding image extraction unit 140 ... read original image data 170 ... print image data 240 ... color measurement target document image signal acquisition unit, 2 2 ... colorimetry target read image signal acquisition unit, 250 ... color conversion table database 252 ... first color conversion table selection unit, 254 ... first color conversion table correction unit, 310 ... printing system

Claims (21)

An image reading unit that reads the target print and obtains read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion unit that converts a signal value of one color space into a chromaticity value of the second color space;
An image association unit that performs a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through the processing by the image association unit and the first color conversion unit, A color conversion table creating unit that creates a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship of
With
The color conversion table creation unit is configured to associate the second color conversion table corresponding to the signal value of the document image data with one or a plurality of grid points of the second color conversion table corresponding to the signal value of the document image data. To set the chromaticity value of the color space of
The color conversion table creation unit uses an existing color conversion table as a temporary color conversion table, and sets the one or more grid points corresponding to the signal values of the document image data with respect to the temporary color conversion table. A color conversion table creation device that performs a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A color conversion table creation apparatus comprising a selection unit that selects a color conversion table to be used as the temporary color conversion table from among the plurality of existing color conversion tables registered in the database. An image reading unit that reads the target print and obtains read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion unit that converts a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion unit. An image association unit for performing a process of associating a positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space that is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association unit, A color conversion table creating unit that creates a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
With
The color conversion table creation unit is configured to associate the second color conversion table corresponding to the signal value of the document image data with one or a plurality of grid points of the second color conversion table corresponding to the signal value of the document image data. To set the chromaticity value of the color space of
The color conversion table creation unit uses an existing color conversion table as a temporary color conversion table, and sets the one or more grid points corresponding to the signal values of the document image data with respect to the temporary color conversion table. A color conversion table creation device that performs a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A color conversion table creation apparatus comprising a selection unit that selects a color conversion table to be used as the temporary color conversion table from among the plurality of existing color conversion tables registered in the database. The selection unit includes:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space, the temporary color conversion table is selected from the plurality of existing color conversion tables registered in the database. The color conversion table creation apparatus according to claim 1, further comprising an automatic extraction unit that automatically extracts a color conversion table to be used. The selection unit includes:
Among the plurality of existing color conversion tables registered in the database, a display unit that displays the temporary color conversion table candidates;
An input device for inputting an instruction for a user to select a color conversion table to be used as the temporary color conversion table from the candidates displayed on the display unit;
The color conversion table creation device according to claim 1 or 2, comprising: The selection unit includes:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space from among the plurality of existing color conversion tables registered in the database, Including an automatic extraction unit that automatically extracts candidates,
The color conversion table creating apparatus according to claim 4, wherein the automatically extracted candidates are displayed on the display unit. An image reading unit that reads the target print and obtains read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion unit that converts a signal value of one color space into a chromaticity value of the second color space;
An image association unit that performs a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through the processing by the image association unit and the first color conversion unit, A color conversion table creating unit that creates a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship of
A color conversion table creation device comprising:
A first color conversion table database storing a plurality of color conversion tables applicable as the first color conversion table;
A first color conversion table selection unit that selects one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
With
The plurality of color conversion tables include a color conversion table representing a correspondence relationship between a read signal of the image reading unit and a chromaticity value for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. Color conversion table creation device. An image reading unit that reads the target print and obtains read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion unit that converts a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion unit. An image association unit for performing a process of associating a positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space that is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association unit, A color conversion table creating unit that creates a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
A color conversion table creation device comprising:
A first color conversion table database storing a plurality of color conversion tables applicable as the first color conversion table;
A first color conversion table selection unit that selects one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
With
The plurality of color conversion tables include a color conversion table representing a correspondence relationship between a read signal of the image reading unit and a chromaticity value for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. Color conversion table creation device. An image reading step of reading the target print and obtaining read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading step and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion step of converting a signal value of one color space into a chromaticity value of the second color space;
An image association step for performing a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through the processing in the image association step and the first color conversion step A color conversion table creating step for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship;
With
In the color conversion table creation step, the second color conversion table corresponding to the signal value of the original image data is associated with one or a plurality of grid points of the second color conversion table corresponding to the signal value of the original image data. A process of setting a chromaticity value of the color space of
In the color conversion table creation step, an existing color conversion table is used as a temporary color conversion table, and the one or more lattice points corresponding to the signal values of the document image data are compared with the temporary color conversion table. A color conversion table creation method for performing a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A color conversion table creation method comprising a step of selecting a color conversion table to be used as the temporary color conversion table from a plurality of the existing color conversion tables registered in the database. An image reading step of reading the target print and obtaining read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading step and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion step of converting a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion step. An image association step for performing a process of associating the positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space that is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association step, A color conversion table creating step for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
With
In the color conversion table creation step, the second color conversion table corresponding to the signal value of the original image data is associated with one or a plurality of grid points of the second color conversion table corresponding to the signal value of the original image data. A process of setting a chromaticity value of the color space of
In the color conversion table creation step, an existing color conversion table is used as a temporary color conversion table, and the one or more lattice points corresponding to the signal values of the document image data are compared with the temporary color conversion table. A color conversion table creation method for performing a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A color conversion table creation method comprising a step of selecting a color conversion table to be used as the temporary color conversion table from a plurality of the existing color conversion tables registered in the database. The step of selecting a color conversion table to be used as the temporary color conversion table is as follows:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space, the temporary color conversion table is selected from the plurality of existing color conversion tables registered in the database. The color conversion table creation method according to claim 8, comprising a step of automatically extracting a color conversion table to be used. The step of selecting a color conversion table to be used as the temporary color conversion table is as follows:
Displaying a candidate for the temporary color conversion table on a display unit from among the plurality of existing color conversion tables registered in the database;
A step of allowing a user to select a color conversion table to be used as the temporary color conversion table from among the candidates displayed on the display unit, and receiving an input of the selection instruction from the user via an input device;
The color conversion table creation method according to claim 8 or 9 including: The step of selecting a color conversion table to be used as the temporary color conversion table is as follows:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space from among the plurality of existing color conversion tables registered in the database, Including automatically extracting candidates,
The color conversion table creation method according to claim 11, wherein the automatically extracted candidates are displayed on the display unit. An image reading step of reading the target print and obtaining read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading step and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion step of converting a signal value of one color space into a chromaticity value of the second color space;
An image association step for performing a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through the processing in the image association step and the first color conversion step A color conversion table creating step for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship;
A color conversion table creation method comprising:
A plurality of color conversion tables applicable as the first color conversion table are stored in a first color conversion table database;
A first color conversion table selection step of selecting one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
The plurality of color conversion tables include a color conversion table representing a correspondence relationship between a read signal of the image reading unit and a chromaticity value for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. How to create a conversion table. An image reading step of reading the target print and obtaining read image data representing the read image of the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading step and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion step of converting a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion step. An image association step for performing a process of associating the positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space that is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association step, A color conversion table creating step for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
A color conversion table creation method comprising:
A plurality of color conversion tables applicable as the first color conversion table are stored in a first color conversion table database;
A first color conversion table selection step of selecting one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
The plurality of color conversion tables include a color conversion table representing a correspondence relationship between a read signal of the image reading unit and a chromaticity value for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. How to create a conversion table. A function of acquiring read image data representing a read image of the target print from an image reading unit that reads the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion function for converting a signal value of one color space into a chromaticity value of the second color space;
An image association function for performing a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through processing by the image association function and the first color conversion function A color conversion table creation function for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship of
Is a program for causing a computer to realize
The color conversion table creation function is configured such that the one or a plurality of grid points of the second color conversion table corresponding to the signal value of the document image data correspond to the signal value of the document image data. Is a function to set the chromaticity value of the color space of
The color conversion table creation function uses an existing color conversion table as a temporary color conversion table, and sets the one or more lattice points corresponding to the signal values of the document image data with respect to the temporary color conversion table. , A program for performing a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A program that causes a computer to realize a selection function for selecting a color conversion table to be used as the temporary color conversion table from among the plurality of existing color conversion tables registered in the database. A function of acquiring read image data representing a read image of the target print from an image reading unit that reads the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion function for converting a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion function. An image association function for performing a process of associating the positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space which is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association function, A color conversion table creation function for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
Is a program for causing a computer to realize
The color conversion table creation function is configured such that the one or a plurality of grid points of the second color conversion table corresponding to the signal value of the document image data correspond to the signal value of the document image data. Is a function to set the chromaticity value of the color space of
The color conversion table creation function uses an existing color conversion table as a temporary color conversion table, and sets the one or more lattice points corresponding to the signal values of the document image data with respect to the temporary color conversion table. , A program for performing a process of setting a chromaticity value of the second color space associated with a signal value of the document image data,
A plurality of color conversion tables that are the existing color conversion tables are registered in a database,
A program that causes a computer to realize a selection function for selecting a color conversion table to be used as the temporary color conversion table from among the plurality of existing color conversion tables registered in the database. The selection function is:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space, the temporary color conversion table is selected from the plurality of existing color conversion tables registered in the database. The program according to claim 15 or 16, comprising a function of automatically extracting a color conversion table to be used. The selection function is:
A function for displaying the provisional color conversion table candidates on a display unit from among the plurality of existing color conversion tables registered in the database;
A function for allowing a user to select a color conversion table to be used as the temporary color conversion table from the candidates displayed on the display unit, and receiving an input of the selection instruction from the user via an input device;
The program according to claim 15 or 16, comprising: The selection function is:
Based on the correspondence between the signal value of the document image data and the chromaticity value of the second color space from among the plurality of existing color conversion tables registered in the database, Including the ability to automatically extract candidates,
The program according to claim 18, wherein the automatically extracted candidates are displayed on the display unit. A function of acquiring read image data representing a read image of the target print from an image reading unit that reads the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion function for converting a signal value of one color space into a chromaticity value of the second color space;
An image association function for performing a process of associating a positional relationship between the read image data represented by the signal value of the first color space and the original image data of the target printed matter;
The original image data represented by the signal value of the third color space which is a device-dependent color space, and the chromaticity value of the read image obtained through processing by the image association function and the first color conversion function A color conversion table creation function for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data based on the correspondence relationship of
Is a program for causing a computer to realize
A plurality of color conversion tables applicable as the first color conversion table are stored in a first color conversion table database;
Causing a computer to realize a first color conversion table selection function for selecting one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
The plurality of color conversion tables include a color conversion table that represents a correspondence relationship between a read signal and a chromaticity value of an image reading unit for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. . A function of acquiring read image data representing a read image of the target print from an image reading unit that reads the target print;
Using the first color conversion table representing the correspondence between the signal value of the first color space obtained from the image reading unit and the chromaticity value of the second color space which is a device-independent color space, the first color conversion table is used. A first color conversion function for converting a signal value of one color space into a chromaticity value of the second color space;
A read chromaticity value image obtained by converting the signal value of the read image data represented by the signal value of the first color space into the chromaticity value of the second color space by the first color conversion function. An image association function for performing a process of associating the positional relationship between the data and the original image data of the target printed matter;
Based on the correspondence between the document image data represented by the signal value of the third color space which is a device-dependent color space and the chromaticity value of the read image obtained through the processing by the image association function, A color conversion table creation function for creating a second color conversion table representing a multidimensional correspondence between the third color space and the second color space of the document image data;
Is a program for causing a computer to realize
A plurality of color conversion tables applicable as the first color conversion table are stored in a first color conversion table database;
Causing a computer to realize a first color conversion table selection function for selecting one color conversion table from the plurality of color conversion tables stored in the first color conversion table database;
The plurality of color conversion tables include a color conversion table that represents a correspondence relationship between a read signal and a chromaticity value of an image reading unit for each combination of a color material type and a base material type used for creating a printed matter by a printing apparatus. .

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