JP2007150757A - Image processor, method for controlling image processor, computer program, and storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain stable printing characteristics by a printer by generating calibration data in consideration of gray balance, even when multiple transfer efficiency changes. <P>SOLUTION: Output of gray patch and colorimetry is performed through a server PC1 constituting a system, and calibration data based on the colorimetry value are created and transmitted to the printer. Printing output can be performed by using the calibration data by the printer. Accordingly, upset of multiple colors, especially of the gray balance due to variations in multiple transfer efficiency by abrupt change in environment such as temperature or humidity can be suppressed and stable color printing can be constantly obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, a control method for the image processing apparatus, a computer program, and a storage medium.

  It is generally known that a color printer connected to a personal computer (PC) and performing color printing in response to a printing command from the PC changes the printing result over time due to changes in its printing characteristics. It has been. Such a change in printing characteristics is generally called a secular change. Aging is considered to occur due to external factors such as the temperature of the printing environment, the humidity, the remaining amount of toner, and the usage of the printer drum. From another point of view, it is known that variations in print characteristics occur between a printer and another printer due to the same external factors even between printers of the same model.

  Under such circumstances, if print data created based on printer characteristics at a certain point is printed at another point, the user may not obtain a desired color print result. Also, since the printing characteristics vary among printers of the same model, the printing results of one printer and other printers may differ, and a desired color printing result may not be obtained.

  In order to solve the above-described problems, conventionally, calibration data for C, M, Y, and K single-color printers as described below is generated and printed.

  In response to an instruction from the server, patch data composed of C, M, Y, and K single-tone gradations is output from the color printer, and the patch data is colorimetrically measured with a densitometer. The server receives the density color measurement result and creates calibration data based on the density curve. The calibration data is transmitted from the server computer to the color printer, and the printer side performs printing using the calibration data.

  Here, the calibration data creation process is executed as follows. FIG. 6 is a diagram for explaining a conventional calibration data creation process.

  In FIG. 6, (a) is an example of a characteristic curve obtained from measured density values of gradation patches of C, M, Y, and K colors. Although only one color is shown here for simplicity, actually, characteristic curves are acquired for the four colors of CMYK. FIG. 6 shows a relationship curve between input and output, which is obtained by interpolation calculation from the measured density value of the gradation patch.

  On the other hand, the ideal value of the density characteristic is defined as a linear curve as shown in FIG. In order to bring the current density characteristic (a) closer to the ideal density (c), a calibration table as shown in FIG. 6B may be obtained as calibration data by an inverse function. That is, by applying the calibration table (b) to the characteristic (a), (c) is obtained as a result.

  In this way, it is possible to reduce variations in print characteristics among a plurality of printing apparatuses.

  However, the calibration data generation described above has the following problems.

First, in the above case, calibration data is generated independently for each color of C, M, Y, and K, so that it is possible to obtain stable output colors at a single color level in CMYK primary color independent calibration. It is. However, to obtain a stable combination of C, M, Y, and K colors, that is, output colors of multi-order colors such as secondary colors and tertiary colors, particularly gray balance, which is an important factor that affects the impression of a photographic image. It is difficult. Also, in electrophotographic printers, the characteristics of multi-order colors may change even when calibrated at the primary color level due to changes in multiple transfer efficiency due to rapid environmental changes.
JP 2001-16451 A

  Thus, conventionally, with the calibration data for each of the C, M, Y, and K colors alone, it has been impossible to obtain a stable multi-order color printing for each color.

  Therefore, an object of the present invention is to make it possible to acquire stable print characteristics in a printer even when the multiple transfer efficiency changes by generating calibration data in consideration of gray balance.

  The present invention for solving the above-described problem is an image processing apparatus connected to a printer, wherein the first reference color component information in a first color space constituting a predetermined gray curve, and the gray curve Storing a first table for associating and registering the second reference color component information in the second color space for printing with the printer, and the first patch in the second color space A color measurement result obtained by measuring a plurality of color measurement images, which are configured by color component information and printed out by the printer, is measured as the second patch color component information in the first color space. The acquisition unit that acquires from the color unit, the first patch color component information, and the second color patch component information are associated with each other and correspond to the first reference color component information in the gray curve. Retrieval means for retrieving the first patch color component information associated with the second patch color component information, the retrieved first patch color component information, and the gray curve in the first table in the gray curve Table generating means for generating a second table by associating the first reference color component information with the second reference color component information associated with the first reference color component information.

  Further, the present invention for solving the above-mentioned problems is an image processing apparatus connected to a printer, for measuring each of a plurality of color component information in the first color space printed out by the printer. Acquisition means for acquiring an image density value; table generation means for generating a calibration table for calibrating the density characteristic of the printer based on the density value to an ideal characteristic; and a first gray curve forming a predetermined gray curve A first table for associating and registering first reference color component information in the second color space and second reference color component information in the first color space for printing out the gray curve by the printer. And a first patch color component information in the first color space, and the calibration table is used. A density result obtained by measuring a plurality of colorimetric images printed out from the printer in the second patch color component information in the calibrated first color space by a density measuring unit is acquired, and the second color is obtained. Color information generating means for generating third patch color component information in space, the first patch color component information, and the third color patch component information are associated with each other, and the first reference in the gray curve Retrieval means for retrieving the first patch color component information associated with the third patch color component information corresponding to the color component information, the retrieved first patch color component information, and the first patch color component information Table generation for generating a second table by associating the second reference color component information associated with the first reference color component information in the gray curve in the table Characterized in that it comprises a stage.

  According to the present invention, it is possible to acquire stable print characteristics in a printer even when the multiple transfer efficiency is changed by generating calibration data in consideration of gray balance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each of the following embodiments, a color laser beam printer (LBP) is used as an example of a printer device constituting the system, but this is merely an example. That is, the present invention can be similarly implemented by a printer other than the LBP. For example, other printer devices such as a color ink jet printer (IJ) or a color bubble jet (BJ) printer (BJ: Color Bubble Jet Printer) can be used.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described in detail.

  FIG. 1 is a block diagram showing an example of the configuration of a printer calibration system according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a server PC (personal computer), which is installed with a software program for realizing the present system. The server PC 1 is connected to the network 5. The server PC 1 exchanges various commands and data relating to calibration with the printer 2 described later via the network 5.

  In the server PC1, reference numeral 11 denotes an internal calibration data storage unit 11, which is used to hold calibration data, which will be described later, inside the server PC1. Reference numeral 111 denotes a calibration table stored in the calibration data storage unit 11.

  A printer 2 connected to the network 5 is a color printing apparatus to be calibrated in this system. The printer 2 is configured to perform printing in accordance with instructions from a plurality of PCs including the client PC 4 connected on the network. A calibration data storage unit 21 is configured inside the printer 2 and is used to hold a calibration table as calibration data, which will be described later, in the printer 2. Reference numeral 211 denotes a calibration table downloaded from the server PC 1 and stored in the calibration data storage unit 21.

  Reference numeral 22 denotes a printer controller configured in the printer 2, which controls various controls relating to the printer 2. The printer controller 22 is also responsible for storing a calibration table (to be described later) in the calibration data storage unit 21 when downloaded from the server PC 1. Reference numeral 23 denotes a printer engine configured in the printer 2 and is basically a portion for outputting print data from the printer controller 22.

  A colorimeter 3 is connected to the server PC 1 and is used to measure the color of patch data output from the printer 2 in this system, but it is not necessary to be connected to the server PC 1 in particular. For example, it is only necessary that the server PC 1 can take in the colorimetric result by using it offline. Reference numeral 4 denotes a client PC connected to the network, which performs creation, editing, and printing instructions of desired print data.

  Next, an example of the hardware configuration of the server PC 1 will be described with reference to FIG. In FIG. 9, reference numeral 901 denotes a CPU which controls the server PC 1 using programs and data stored in a RAM (Random Access Memory) 902 and a ROM (Read Only Memory) 905 and performs processing corresponding to the present invention. Do. Reference numeral 902 denotes a RAM which includes an area for reading a processing program stored in the internal storage device 907 and a work area used when the CPU 901 executes various processes.

  Reference numeral 903 denotes an input unit that receives input from the administrator of the server PC 1 and includes a keyboard and a mouse. A communication I / F (interface) 904 functions as an I / F for connecting to the network 5 or the colorimeter 3. A ROM 905 stores a program (for example, a boot program) for controlling the entire server PC 1 and the like. Reference numeral 906 denotes a display unit as a display screen, which includes a CRT or a liquid crystal screen.

  Reference numeral 907 denotes an internal storage device that is mainly composed of a hard disk and stores a program for performing transaction processing corresponding to a flowchart of predetermined processing corresponding to the present embodiment and various application data. In addition, a calibration data storage unit 11 is provided and a calibration table 111 is also stored. A color separation table, which will be described later, is also stored for creating a calibration table. The data stored here is read out to the RAM 902 as necessary. Reference numeral 908 denotes a bus connecting the above-described units.

  The client PC 4 can also be implemented with an equivalent configuration. Therefore, FIG. 9 is used for the hardware configuration of the client PC 4. In the present embodiment, the internal storage device 907 need not include the calibration storage unit 11.

  In the above configuration, a flow when performing calibration (calibration) will be described with reference to FIGS. 2, 3, and 4.

  First, the flow of processing when image processing is performed using the calibration table 211 in the printer controller 22 in the printer 2 as a color printing apparatus will be described with reference to FIG.

  First, in step S301, color fine adjustment is performed on the input signal RGB. The color fine adjustment includes brightness correction and contrast correction. Next, in step S302, color matching processing is performed. The color matching process is a process for matching the color of the monitor with the color of printer printing.

  Next, in step S303, color separation processing is performed. The color separation process is a process for converting luminance RGB as an input signal into density CMYK as a print signal of the printer. At this time, a color separation table as shown in FIG. 19A is used. This color separation table is stored in a predetermined internal storage device in the printer 2 accessible by the printer controller 22.

  FIG. 19 a shows a color separation table 1900. The color separation table 1900 is a table that registers each input value (0 to 255) in the RGB color space in association with each output value (0 to 255) in the CMYK color space. This color separation table 1900 is a colorimetric value in an L * a * b * color space that forms an ideal gray curve, which will be described later with reference to FIG. 5, when data in the CMYK color space is printed out by the printer 2. Is designed to be obtained. That is, in the color separation table 1900, an input RGB value and a CMYK value are associated with each other using the L * a * b * value of the gray curve as a reference value.

  Next, in step S304, calibration processing is performed. In the calibration process, CMYK 8-bit multilevel signals are input / output signals, and output characteristics are corrected using a calibration table 211 stored in the calibration data storage unit 21. In step S305, halftone processing is performed to convert the CMYK 8-bit signals into signals in accordance with the output system. Here, in general, binarization into a CMYK 1-bit signal is performed.

  FIG. 2 is a flowchart of processing for creating a calibration table and downloading the table to the printer 2 in the server PC 1 constituting the system.

  First, in step S201, the server PC 1 instructs the printer 2 to output patch data. In the printer 2, patch data is output in response to an instruction from the server PC1.

  An example of the patch data output from the printer 2 is as shown in FIG. In FIG. 8, 9 × 10 patch groups 801 in the vertical and horizontal directions are arranged in two vertical positions in one A4 size page (800). That is, in FIG. 8, 802 is the minimum unit patch, and the patch group 801 is an aggregate of a total of 180 patches. In FIG. 8, the reason why 90 patches are arranged in two places at the top and bottom is to take the average of the top and bottom in consideration of in-plane unevenness of the output product of the printer 2. Each patch 802 in FIG. 8 is a so-called gray patch as a colorimetric image composed of mixed colors of CMY or CMYK.

  Next, the contents of the calibration process considering the patch 802 and the gray balance will be described. FIG. 5 is a diagram illustrating an example of an ideal gray curve. 5A shows a target curve of lightness L * with respect to an input value, and FIG. 5B shows a target curve of saturation and hue a * and b * with respect to the input value.

  Here, it is desirable that the ideal gray curve is defined in advance. The gray curve defining method may be defined, for example, by performing a user test or the like, or may be defined only by the L * curve with a *, b * = 0. Then, as described above, the parameters of the color separation table 1900 used in step S303 in FIG. 3 are designed according to the gray curve thus defined.

  In this way, even when the color separation table 1900 is designed so as to obtain an ideal gray curve, when the characteristics of the printer 2 change due to environmental changes or secular changes, The output corresponding to the ideal gray curve cannot be obtained. On the other hand, if the calibration process corresponding to this embodiment is executed, an output result corresponding to an ideal gray curve can be obtained by correction.

  FIG. 4 shows a color separation step S303 and a halftone step S305 extracted from the flow of image processing that operates in the printer 2 described with reference to FIG. Since the calibration in step S304 is skipped in the patch output in the calibration shown in the present invention, step S304 is indicated by a dotted line.

  The basic concept of this calibration is shown. First, RGB (0 to 255) in which RGB representing gray is equivalent is input to the color separation table 1900 of S303, and C1, M1, Y1, and K1 (0 to 255) are obtained based on the registered values of 1902. . Further, 1-bit C1 ′, M1 ′, Y1 ′, and K1 ′ obtained by halftoning the C1, M1, Y1, and K1 through step S305 are output to the engine, and the measured value L * of the patch is output. a * b * (0-255) is obtained.

  Originally, the measured value L * a * b * (0 to 255) obtained here is a value registered in 1903 in the color separation table 1900 in association with the C1, M1, Y1, and K1. Should match. However, if the characteristics of the printer 2 change due to environmental changes or changes over time, this coincidence cannot be obtained.

  Therefore, the measured value L * a * b * (0 to 255) for the input RGB value (0 to 255) is the ideal Lt * at * bt * (0 to 0) associated with the RGB value in the color separation table 1900. 255) is created. The created calibration table is used in step S304 to perform calibration processing.

  That is, the calibration table used in step S304 has C2, M2, Y2, K2 (Lt * at * bt * (0 to 255) obtained for RGB values (0 to 255). 0 to 255).

  For this purpose, each patch 802 shown in FIG. 8 is used to search for a combination of CMYK for obtaining an ideal gray curve. The number of patches included in the patch group includes a predetermined number of gradations C2, M2, Y2, and K2 for obtaining an ideal gray curve derived in advance before the characteristic variation, and surrounding CMYK values derived by assuming the variation. It is determined based on. In FIG. 8, the number of patches is 90 × 2, but this is an example, and the number of patches is not limited to this.

  The patch data 800 is output from the printer 2 in response to an instruction from the server PC 1 in step S201 in FIG. At this time, information constituting patch data of the above format in the printer 2 may be previously held, and patch data may be generated based on the information in response to an instruction from the server PC 1. Further, the patch data may be generated by transmitting the patch data configuration information to the printer 2 on the server PC 1 side. The patch data configuration information depends on the command system owned by the printer 2, but is not mentioned here.

  Next, in step S202 of FIG. 2, the color measurement of the patch data output by the colorimeter 3 is performed. The colorimeter 3 acquires the L * a * b * signal value of each patch of the above-described patch data and returns the value to the server PC1. The server PC 1 calculates an average from the input value based on the patch arrangement of the patch data, and obtains the relationship between 90 colors and Lab by the combination of CMYK as a result.

  Next, in step S203, an L * a * b * table for all gray levels near gray is created by interpolation. This table is created using tetrahedral interpolation or cube interpolation from the relationship between the 90 colors of CMYK and L * a * b *. An example of the correspondence table created here is as shown in FIG. 19b. In the correspondence table 1910, the CMYK value (1911) and the L * a * b * value (1912) are registered in association with each other.

  Next, in step S204, the correspondence table 1910 associates the L * a * b * value (1912) closest to the registered value 1903 in the color separation table 1900 corresponding to the predetermined value of the gray curve in FIG. The CMYK value (1911) is searched. The CMYK values searched here are Ci, Mj, Yk, and Kl. At this time, Ci, Mj, Yk, and Kl are specified as points that minimize the sum of squares of the difference between the corresponding L * a * b * and the target L * a * b *.

  In step S205, the CMYK registration value 1902 associated with the L * a * b * registration value 1903 in the color separation table 1900 corresponding to the target L * a * b * is used as the above Ci, Mj, Yk, Kl. Create a table that will be proofread. An example of the calibration table created here is as shown in FIG. 19c. In the calibration table 1920, a value corresponding to the CMYK registration value 1902 of the color separation table 1900 is registered in 1921. In 1922, the values of Ci, Mj, Yk, and Kl searched in step S204 are registered. This creation processing corresponds to the calibration table creation processing described with reference to FIG. As a result, calibration is performed so that C2, M2, Y2, and K2 (0 to 255) that can obtain an ideal Lt * at * bt * (0 to 255) are output with respect to an input of RGB values 0 to 255. Configuration table can be configured. The table may be prepared for each color of CMYK.

  Steps S204 and S205 are performed for all gradations from 0 to 255. The calibration table created in this way is downloaded from the server PC 1 to the printer 2 in step S 206 and stored in the calibration data storage unit 21. This download can be performed by transmitting the download command including the calibration data from the server PC 1 to the printer 2. Although the command depends on the command system of the printer 2, a well-known technique may be applied, and a detailed description thereof is omitted here.

  Next, the processing flow of the printer controller 22 when the printer 2 receives predetermined data including the calibration table from the server PC 1 will be described with reference to FIG.

  In step S701 in FIG. 7, it is determined whether or not data has been received. If no data is received, step 701 is continued to monitor data reception. If data is received, data analysis is performed based on the transmission command in step S702. In step S703, when it is determined that the calibration table is transmitted from the server PC1 based on the analysis result in step S702, the process proceeds to step S704. In step S <b> 704, the calibration data is registered as the calibration table 211 in the calibration data storage unit 21. On the other hand, if it is determined in step S703 that it is not a calibration table, corresponding processing is performed in step S705.

  The print data is normally transmitted from the application on the server PC 1 to the printer 2 via the printer driver on the server PC 1. The printer controller 22 in the printer 2 performs analysis of print data, page layout configuration, image processing, printing, etc. in step 705 of FIG. The flow of processing when performing image processing using calibration data in the printer controller 22 is as described with reference to FIG.

  In this way, the flow of calibration that operates between the computer apparatus and the color printing apparatus that constitute the system has been described.

  Next, the overall flow of processing such as calibration data creation / deletion will be described with reference to FIG.

  First, in step S1001, a main screen as shown in FIG. 11 is displayed on the display unit 906 of the server PC1.

  In FIG. 11, the following three selection items are displayed on the screen 1020. First, “new creation” 1021 is an item selected when creating new calibration data. Next, “open measurement data file” 1022 is an item selected when a saved measurement data file is called. Furthermore, “delete download data” 1023 is an item selected when the downloaded calibration data is deleted. In addition, buttons “Return” 1024, “Next” 1025, “Cancel” 1026, and “Help” 1027 are displayed below the screen 1020.

  In FIG. 11, when any of the above items is selected and the operation of the “next” button 1025 is accepted, the screen moves to another related screen.

  Returning to FIG. 10, in step S <b> 1002, selection of any of “New creation” 1021, “Open measurement data file” 1022, and “Delete download data” 1023 is accepted on the screen 1020. If the “cancel” button 1026 is selected, the process is terminated, and if the “help” button 1027 is selected, a help screen is displayed.

  If the selection of “create new” 1021 is accepted in step S1002, the process proceeds to step S1003. In step S1003, calibration processing with an emphasis on gray balance shown in FIG. 2 is performed. That is, the calibration data is created and the created data is transmitted to the printer 2. Next, in step 1004, selection is made as to whether or not to save the measurement data in the colorimeter 3 in the internal storage device 907 in the calibration process in step S1003. If storage of measurement data is selected (“YES” in step S1004), the process proceeds to step S1005 and the measurement data is stored in the internal storage device 907. If saving is not selected (“NO” in step S1004), the process ends without saving.

  Next, when selection of “open measurement data file” 1022 is accepted in step S1002, the process proceeds to step S1006. In step S1006, a screen for accepting designation of measurement data to be read is displayed, and measurement data corresponding to the designation is read from the internal storage device 907 to the RAM 902. The measurement data read out here is data stored in the internal storage device 907 in step S1005. Next, the process proceeds to step S1003, and a calibration process using the read measurement data is executed. Thereafter, the process ends without overwriting the measurement data.

  Next, when selection of “delete download data” 1023 is accepted in step S1002, the process proceeds to step S1007, and a command for instructing deletion of the calibration table 211 is transmitted to the printer 2. Details of this command are omitted. Thereafter, the process ends. In the printer 2, the calibration table 211 in the calibration data storage unit 21 is deleted in response to the reception of the command.

  According to the above configuration, the user can output the gray patch and perform color measurement via the server PC 1 constituting the system, create calibration data based on the color measurement value, and transmit the calibration data to the printer 2. . On the printer side, printing output can be performed using the calibration data. Therefore, it is possible to suppress the disruption of multi-order colors, especially gray balance, caused by fluctuations in multiple transfer efficiency due to rapid changes in the environment such as temperature and humidity, and a unique color printing that can always provide stable color printing. The effect is obtained.

  In the present embodiment, since the gray balance can be set to an ideal value that is defined in advance, higher-definition image processing can be realized.

[Modification 1 of the first embodiment]
Next, Modification 1 of the first embodiment will be described.

  FIG. 12 is a block diagram illustrating an example of the configuration of a printer calibration system according to this modification.

  The system configuration shown in FIG. 12 is basically the same as the system configuration shown in FIG. However, the printer 2 does not need to include the calibration data storage unit 21.

  This modification differs from the first embodiment in that image processing including calibration processing shown in FIG. 3 is executed in the server PC 1 instead of in the printer 2. That is, the printer 2 does not need to acquire the calibration table 111 from the server PC 1 and perform the calibration process in the printer controller 22 as in the first embodiment. Then, print data obtained as a result of the calibration processing in the server PC 1 is acquired and printing is performed.

  Therefore, in this modification, instead of downloading the calibration data in step S206 in the process corresponding to FIG. 2, the calibration table generated is stored in the calibration data storage unit 11 in the server PC1.

[Modification 2 of the first embodiment]
Next, a second modification of the first embodiment will be described. The system configuration in this modification is the same as the system configuration shown in FIG.

  3 is different from the first embodiment in that the calibration process shown in FIG. 3 is executed not in the printer 2 but in the client PC 4. In the present modification, the printer 2 acquires the calibration table 111 from the server PC 1 as in the first embodiment and stores it as the calibration table 211 in the calibration data storage unit 21. Next, the client PC 4 acquires the calibration table 211 and the color separation table 1900 from the printer 2, and executes the image processing shown in FIG. 3 in the client PC 4. The print data as the execution result is transmitted to the printer 2, and the printer 2 performs printing using the print data.

[Modification 3 of the first embodiment]
Next, Modification 3 of the first embodiment will be described. In the first embodiment, the gray curve in FIG. 5 is treated as an ideal one. On the other hand, this modification is characterized in that it is used as a gray curve obtained by actual measurement.

  5A, reference numeral 501 denotes a target curve of lightness L * with respect to the input value, and reference numeral 502 of FIG. 5B denotes target curves of saturation and hue a *, b * with respect to the input value. Further, 503 is paper white, 504 is black of the maximum density, and 505 indicates gray of an intermediate input value.

  Next, how to obtain the gray curve will be described with reference to FIG. When obtaining the gray curve, it is desirable to use a reference printer or the like having as stable characteristics as possible, which is used when designing the color processing parameters of each image processing step described in FIG.

  FIG. 13 shows a color separation step S303, a calibration processing step S304, and a halftone processing step S305 extracted from the flow of image processing that operates in the color printing apparatus 2 described with reference to FIG. In step S303, RGB values 0 to 255 are input. This input value is converted into C1, M1, Y1, and K1 by color separation according to a general color separation rule. In subsequent step S304, calibration is applied to obtain C2, M2, Y2, and K2. In this case, the calibration in step S304 is the CMYK primary color calibration described in the conventional example with reference to FIG.

  Next, the obtained C2, M2, Y2, and K2 are input to the halftone processing step of step S305, and the obtained value is printed out from the printer engine 23.

  A gray curve of the reference printer can be formulated by actually measuring the print output result with the colorimeter 3. However, the actual measurement values are partially discontinuous due to normal measurement errors. However, by making a smooth curve by smoothing or the like, a gray curve as shown in FIG. 5 can be obtained. The predetermined value in the gray curve thus obtained is registered in 1903 of the color conversion table 1900, and the corresponding C2, M2, Y2, K2 values, values obtained by linear interpolation or the like are registered in 1902. In addition, the corresponding RGB value is registered in 1901. Thereby, color conversion based on the actual measurement value can be performed.

[Modification 4 of the first embodiment]
Next, Modification 4 of the first embodiment will be described. In the first embodiment, the color of the patch is measured using the colorimeter 3, and a calibration table is created. On the other hand, this modification is characterized in that a scanner is used instead of the colorimeter 3.

  In this modification, instead of the color measurement processing in step S202 of FIG. 2, the patch data output by the scanner is scanned, the RGB signal values for each patch are read, and passed to the server PC1. The server PC 1 converts the obtained RGB signal values into L * a * b *, which is a device-independent signal. Although the conversion is not described in detail here, a conversion method using a neural network, conversion from a device RGB to L * a * b * by color matching, and the like are conceivable.

  Note that patch scanning by the scanner is normally executed through a scanner driver configured on the server PC 1. Therefore, the scanner driver can set the scan resolution and specify the input area.

  When scanning with a scanner, the scanner itself is calibrated. This is a calibration unique to the device of the scanner. For example, white calibration or the like can be performed by scanning a white plate or white band provided in the scanner.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the first embodiment, calibration is performed with emphasis on gray balance. However, in this embodiment, by performing the primary color calibration in advance before the calibration, a more accurate calibration is performed later. Is possible.

  The system configuration corresponding to this embodiment is as shown in FIG. The configuration shown in FIG. 16 is substantially the same as the configuration shown in FIG. 1 in the first embodiment, and the same reference numerals are assigned to the blocks equivalent to those in FIG. About these, description regarding FIG. 1 applies mutatis mutandis and description is abbreviate | omitted.

  In FIG. 16, a scanner 1601 is used instead of the colorimeter 3 shown in FIG. A scanner 1601 is connected to the server PC 1 and is used to measure a calibration chart output from the printer 2 in this system. However, it can also be used for the original purpose of the scanner, such as document input.

  Next, a calibration process corresponding to this embodiment will be described. Since the flow of image processing in the print controller 22 of the printer 2 in this embodiment is the same as that shown in FIG. 3 in the first embodiment, description thereof is omitted here.

  Next, an example of creating a calibration table that operates on the server PC 1 and downloading the table to the printer 2 will be described with reference to FIG.

  First, in step S1701, primary color calibration is performed. In this primary color calibration, in accordance with an instruction from the server PC 1, first, patch data composed of C, M, Y, K single-color gradations as shown in FIG. 14 is output from the printer 2. The patch data is read by the scanner 1601 and the read value is converted into a density value. In the server PC1, as shown in FIG. 6, in order to bring the current density characteristic (a) or (b) closer to the ideal density (c), 1 corresponding to FIG. 6 (b) or (a) is obtained by an inverse function. Next color calibration table is obtained. This calibration table is transmitted to the printer 2 and stored in the calibration data storage unit 211. An example of the configuration of the primary color calibration table is as shown in FIG. 19d, for example. In FIG. 19d, reference numeral 1930 denotes a primary color calibration table. In the table, C ', M', Y ', and K' output values are registered in association with C, M, Y, and K input values (0 to 255).

  FIG. 14 is a diagram showing an example of a printer chart used in such calibration. In FIG. 14, the printer chart is A4 size. In addition, a total of 1024 patch units are prepared by dividing each page vertically and horizontally into 32 pages. In the horizontal direction, patch units are arranged for cyan (C), magenta (M), yellow (Y), and black (K), which are basic colors of the printing toner.

  The numerical value described in each patch unit indicates a subscript of the array, and the relationship between the subscript and the actual numerical value is configured as shown in a table shown in FIG. That is, the actual output data in the array 0 is 0, the actual output data in the array 32 is 128, and the actual output data in the array 63 is 255. A numerical value from 0 to 255 is used in an 8-bit system for each color of CMYK. However, when the number of bits is different, the numerical value in the correspondence table of FIG. 15 may be changed.

  In FIG. 14, patch units are arranged at four highlights in the arrangements 0 to 31 at four locations, and shadows in the arrangements 33 through 63 are arranged at eight locations in the 16 gradations. The reason why the number of gradations differs between the highlight and the shadow is that in this system, the highlight side requires more detailed gradation information than the shadow side. This is also because the variation in input values in the scanner 1601 tends to be larger on the shadow side than on the highlight side.

  In this way, by performing the primary color calibration in advance before performing the calibration with emphasis on the gray balance in the next phase, calibration with higher accuracy can be obtained in the subsequent stage.

  Next, in steps S1702 to S1707, basically the same processing as that performed in steps S201 to S206 in FIG. 2 in the first embodiment is executed.

  However, in the first embodiment, the colorimeter 3 is used instead of the scanner 1601. Therefore, in the processing corresponding to the present embodiment, the patch data output by the scanner 1601 is scanned, the RGB signal values for each patch unit are read, and transmitted to the server PC1. The server PC 1 performs conversion from the obtained RGB signal value to L * a * b *, which is a device-independent signal. The conversion is not described in detail here, but a conversion method using a neural network, conversion from device RGB to L * a * b * by color matching, and the like are conceivable.

  Further, in patch output at the time of calibration considering gray balance, calibration processing is performed in step S304 after color separation in step S303 in the image processing flow described with reference to FIG. In this calibration process, the primary color calibration table 1930 generated in step S1701 stored in the calibration data storage unit 211 is used.

  In this way, primary color calibration is performed in step S304, and patch output is performed via the halftone process in step S305.

  In the overall flow of the calibration data creation / deletion process shown in FIG. 10, the primary color calibration in step S1701 is executed before the calibration in which the gray balance is emphasized in step S1003. Is done.

  Thus, according to the present embodiment, more stable color printing can be obtained by performing calibration in consideration of gray balance after performing independent primary color level calibration for CMYK. . In addition, since the scanner can be used as a colorimeter, low-cost calibration can be realized.

[Third Embodiment]
In the second embodiment, the calibration considering the gray balance is performed after the CMYK independent primary color level calibration is performed. On the other hand, in this embodiment, the CMYK can be selected by the user depending on whether or not to perform the calibration considering the gray balance after the independent primary color level calibration.

  The system configuration in this embodiment is equivalent to the configuration shown in FIG. 16 in the second embodiment. Also, the creation of the calibration table operating on the server PC 1 and the process of downloading the table to the printer 2 are almost the same as in FIG. However, the user can set in advance whether or not to perform the calibration considering the gray balance after the primary color calibration. Such setting can be performed on the main screen shown in step S1001 in the overall flow of processing such as calibration data creation / deletion shown in FIG.

  FIG. 18 is a diagram illustrating a display example of the main screen corresponding to the present embodiment. Screen 1800 is basically the same as screen 1020 in FIG. 11, but differs in that “new creation 1” 1801 and “new creation 2” 1802 are displayed. “New creation 1” 1801 is an item selected when new primary color calibration data is created. In this case, only primary color calibration is executed. On the other hand, “New creation 2” 1802 is an item selected when creating calibration data with an emphasis on gray balance. In this case, calibration with an emphasis on gray balance is executed after the primary color calibration. Is done.

  As described above, according to the present embodiment, the CMYK can independently select the primary color level calibration and the calibration in consideration of the gray balance according to the purpose. Color printing is possible.

[Other Embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  The object of the present invention can also be achieved by supplying a storage medium storing software program codes for realizing the above-described functions to the system, and the system reading and executing the program codes. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. In addition, an operating system (OS) running on a computer performs part or all of actual processing based on an instruction of the program code, and the above-described functions are realized by the processing.

  Furthermore, you may implement | achieve with the following forms. That is, the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer. Then, based on the instruction of the program code, the case where the above-described functions are realized by the CPU included in the function expansion card or the function expansion unit performing part or all of the actual processing is also included.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

1 is a block diagram illustrating an example of a configuration of a printer calibration system corresponding to a first embodiment of the present invention. It is a flowchart which shows an example of the calibration data generation process etc. corresponding to the 1st Embodiment of this invention. 4 is a flowchart illustrating an example of image processing in the printer controller 22 of the printer 2 corresponding to the first embodiment of the present invention. It is a figure for demonstrating the calibration process corresponding to the 1st Embodiment of this invention. It is a figure which shows the example of the ideal gray curve based on this invention. It is a figure for demonstrating an example of the conventional calibration process. 6 is a flowchart illustrating an example of processing when a calibration data download command is received by the printer 2 according to the first embodiment of the present invention. It is a figure which shows an example of the patch data corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of the hardware constitutions of server PC1 corresponding to embodiment of this invention. It is a flowchart which shows an example of the whole flow of processes, such as calibration data creation and deletion, corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of the screen displayed on the display part 906 of server PC1 corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of the printer calibration system corresponding to the modification 2 of the 1st Embodiment of this invention. It is a figure for demonstrating how to obtain | require the gray curve in the modification 2 of the 1st Embodiment of this invention. It is a figure which shows an example of the chart for printers used in the primary color calibration of the 2nd Embodiment of this invention. It is a figure which shows the relationship between the numerical value described in the patch unit of the chart shown in FIG. 14, and output data. It is a figure which shows an example of the printer calibration system corresponding to the 2nd Embodiment of this invention. It is a flowchart which shows an example of the calibration data generation process etc. corresponding to the 2nd Embodiment of this invention. It is a figure which shows an example of the screen displayed on the display part 906 of server PC1 corresponding to the 3rd Embodiment of this invention. It is a figure which shows an example of a structure of the color separation table 1900 corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of a structure of the corresponding | compatible table 1910 corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of a structure of the calibration table 1920 corresponding to the 1st Embodiment of this invention. It is a figure which shows an example of a structure of the primary color calibration table 1930 corresponding to the 2nd Embodiment of this invention.

Claims (12)

A first table for registering the first reference color component information in the first color space constituting the predetermined gray curve in association with the second reference color component information in the second color space is stored. Storage means;
Colorimetric results obtained by measuring the colorimetric images of a plurality of colorimetric images, which are configured by the first patch color component information in the second color space and printed out by a printer, are displayed in the first color space. Obtaining means for obtaining second patch color component information;
The first patch color component information is associated with the second color patch component information, and are associated with the second patch color component information corresponding to the first reference color component information in the gray curve. Search means for searching for the first patch color component information;
The first patch color component information retrieved is associated with the second reference color component information associated with the first reference color component information in the gray curve in the first table to associate a second An image processing apparatus comprising: table generation means for generating a table.   The image processing apparatus according to claim 1, further comprising a first transmission unit configured to transmit the second table to the printer. Connected to the client device,
In the first table, third reference color component information in a third color space corresponding to the second reference color component information is further associated and registered,
Data acquisition means for acquiring first print data composed of color space information in a third color space for printing out from the client device in the printer;
Data conversion means for converting the first print data into second print data composed of color component information in the second color space using the first table and the second table; ,
The image processing apparatus according to claim 1, further comprising a second transmission unit configured to transmit the second print data to the printer. An image processing apparatus connected to a printer,
Obtaining means for obtaining a density value of a measurement image printed out by the printer for each of a plurality of pieces of color component information in the first color space;
Table generating means for generating a calibration table for calibrating the density characteristic of the printer based on the density value to an ideal characteristic;
First reference color component information in a second color space constituting a predetermined gray curve, and second reference color component information in the first color space for printing out the gray curve by the printer Storage means for storing a first table for registering
Printed by the printer in the second patch color component information in the first color space, which is composed of the first patch color component information in the first color space and calibrated using the calibration table. A color information generating unit that acquires density results obtained by measuring the plurality of colorimetric images by the density measuring unit and generates third patch color component information in the second color space;
The first patch color component information and the third color patch component information are associated with each other, and are associated with the third patch color component information corresponding to the first reference color component information in the gray curve. Search means for searching for the first patch color component information;
The first patch color component information retrieved is associated with the second reference color component information associated with the first reference color component information in the gray curve in the first table to associate a second An image processing apparatus comprising: table generation means for generating a table. A selection receiving means for receiving selection of whether to generate the second table after generating the calibration table;
If the selection to generate the second table is accepted, the second table is generated,
5. The image processing apparatus according to claim 4, wherein when the selection not to generate the second table is received, only the first table is generated. 6. A first table for registering the first reference color component information in the first color space constituting the predetermined gray curve in association with the second reference color component information in the second color space is stored. A method for controlling a server device including a storage unit,
A color measurement result obtained by measuring a plurality of color measurement images, which are configured by the first patch color component information in the second color space and printed out by a printer, is measured in the first color space. An acquisition step of acquiring as second patch color component information;
The first patch color component information is associated with the second color patch component information, and are associated with the second patch color component information corresponding to the first reference color component information in the gray curve. A search step for searching for the first patch color component information;
The first patch color component information retrieved is associated with the second reference color component information associated with the first reference color component information in the gray curve in the first table to associate a second A control method for an image processing apparatus, comprising: a table generation step for generating a table.   The method according to claim 6, further comprising a first transmission step of transmitting the second table to the printer. The image processing device is connected to a client device;
In the first table, third reference color component information in a third color space corresponding to the second reference color component information is further associated and registered,
The method
A data acquisition step of acquiring first print data composed of color space information in a third color space for printing out from the client device in the printer;
A data conversion step of converting the first print data into second print data composed of color component information in the second color space using the first table and the second table; ,
The image processing apparatus control method according to claim 6, further comprising a second transmission step of transmitting the second print data to the printer. First reference color component information in a first color space that is connected to the printer and forms a predetermined gray curve, and a second in the second color space for printing out the gray curve by the printer. A control method of an image processing apparatus including a storage unit that stores a first table that registers and associates reference color component information with each other,
An acquisition step of acquiring a density value of a measurement image printed out by the printer for each of a plurality of color component information in the second color space;
A table generating step for generating a calibration table for calibrating the density characteristic of the printer based on the density value to an ideal characteristic;
Printed from the printer in the second patch color component information in the second color space, which is composed of the first patch color component information in the second color space and calibrated using the calibration table. A color information generation step of acquiring density results obtained by measuring a plurality of colorimetric images by a density measurement unit, and generating third patch color component information in the first color space;
The second patch color component information is associated with the third color patch component information, and are associated with the third patch color component information corresponding to the first reference color component information in the gray curve. A search step for searching for the first patch color component information;
The first patch color component information retrieved is associated with the second reference color component information associated with the first reference color component information in the gray curve in the first table to associate a second A control method for an image processing apparatus, comprising: a table generation step for generating a table. A selection receiving step of receiving selection of whether to generate the second table after generating the calibration table;
If the selection to generate the second table is accepted, the second table is generated,
The method according to claim 9, wherein only the first table is generated when a selection not to generate the second table is received.   A computer program for causing a computer to execute the method according to claim 6.   A computer-readable storage medium storing the computer program according to claim 11.

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