JP4010952B2 - Color conversion definition creation method, color conversion definition creation device, and color conversion definition creation program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a color conversion that creates a color conversion definition that represents a correspondence between coordinates in a target color space that depends on a target device and restricted coordinates on the output device that depend on the output device and in which the sum of coordinate components is limited. The present invention relates to a definition creation method, a color conversion definition creation device, and a color conversion definition creation program that, when executed in a computer, causes the computer to operate as a color conversion definition creation device.
[0002]
[Prior art]
Conventionally, in printing using a color printing machine, four color inks are used, in which K (black) ink is added to C (cyan), M (magenta), and Y (yellow) ink. All colors are expressed by being superimposed. Originally, it should be possible to express all colors with only C, M, and Y inks, but there is a problem that even if these three inks are mixed, a sufficiently dark black cannot be obtained. K ink is used to express deep black.
[0003]
In recent years, K ink has been widely used not only for expressing dark black but also for applying a technique called UCR (Under Color Removal) (see, for example, Patent Document 1). UCR is a technique for reducing the total amount of ink overlaid by replacing the gray component expressed by C, M and Y inks with K ink. Usually, in UCR, for example, a color represented by a dot area ratio of (C, M, Y, K) = (60%, 70%, 80%, 0%) is selected from among the components of the color. Replace 60% of each of C, M, and Y with the same amount of K60%, and (C, M, Y, K) = (0%, 10%, 20%, 60%) halftone dot area ratio It is done to express in. If the color is expressed by the dot area ratio before performing the UCR, 210% of the ink is overlaid with all the inks combined. However, if the color is expressed by the dot area ratio after performing the UCR, the color is superimposed. The amount of ink to be sprinkled can be reduced to 90%. If a lot of ink is overlaid on the paper, there may be problems such as cracking when the ink dries or film peeling that causes the ink to peel off. By limiting the total amount of ink to be afflicted, these problems can be avoided.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-124234
[0005]
[Problems to be solved by the invention]
However, in the above-described UCR, for example, in the color near the shadow (the part near K = 100%), for example, the network of (C, M, Y, K) = (60%, 70%, 80%, 90%). If the UCR process is applied to the color expressed by the dot area ratio, the halftone dot area ratio will be (C, M, Y, K) = (0%, 10%, 20%, 150%). As described above, the halftone dot area ratio of the K ink after replacing the C, M, and Y inks with the K ink exceeds 100% in calculation, and the UCR process may not be performed.
[0006]
Furthermore, when a method for limiting the total amount of ink, such as UCR, is applied to an output device that outputs an image, compared to a case in which the total amount of ink is not limited, a color region that can be reproduced by the output device ( Color reproduction area) may become narrow. This causes inconvenience particularly when creating a proof image described below.
[0007]
Printing using a color printing machine is a large and costly operation such as preparing a film original plate and further preparing a printing plate. Therefore, before printing, use a printer that is simpler than a color printer to create a proof image that is as similar as possible to the color of the color image printed by the color printer. The color and layout of color images are checked in advance using images. When creating a proof image, colors that are in the color reproduction area of the color printing machine but not in the color reproduction area of the printer are colors that cannot be represented by the printer. Is replaced with a color in the color reproduction area of the printer. When the total amount of ink to be overlaid is limited by applying a conventional method such as UCR, the color reproduction area of the printer becomes narrower than when the total amount of ink is not limited. The probability of occurrence of substitution increases, and the color reproducibility in the printer deteriorates. If the color reproducibility of the printer deteriorates, the color of the proof image will be different from the color of the color image, or the part where the color changes continuously in the color image will cause a discontinuous color change in the proof image. Thus, there is a problem that it is difficult to achieve the original purpose of the proof image, that is, prior confirmation of the color of the color image.
[0008]
In view of the above circumstances, the present invention provides a color conversion definition creation method, a color conversion definition creation apparatus, and a color conversion definition creation that create a color conversion definition that can limit the total amount of ink while maintaining a color reproduction region in an output device. The purpose is to provide a program.
[0009]
[Means for Solving the Problems]
The color conversion definition creating method according to the present invention includes a target coordinate on a target color space depending on a target device that outputs an image based on image data, and a proof image that reproduces the target image when the image is obtained by the target device. A color that creates a color conversion definition that indicates the correspondence with the limit coordinates that exist in the output device color space that depends on the output device that outputs based on and the sum of the coordinate components that make up the coordinates is limited to a predetermined limit value or less In the conversion definition creation method,
A correspondence acquisition process for acquiring a correspondence relationship between the limit coordinates and the colorimetric coordinates in the device-independent colorimetric color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, the correspondence is within the limit coordinate range associated with the colorimetric coordinates by the correspondence acquired in the correspondence acquisition process. A coordinate search process for searching for limited coordinates whose colorimetric coordinates are closer to the reference;
And a color conversion definition creating process for creating a color conversion definition by associating the target coordinates with the limited coordinates searched in the coordinate search process.
[0010]
Conventionally, in the field of printing, a proof image that resembles the color of a color image printed by a printing press as closely as possible is created by a printer or the like, and the color of the color image is confirmed in advance using the proof image. Has been done. However, if the amount of ink superimposed when creating a proof image is limited by applying a method such as UCR that has been used in the past, the color reproduction area of the printer will be narrowed, and color reproducibility will be reduced. There is a problem that the color of the proof image is greatly different from the color of the actually printed color image due to deterioration.
[0011]
The color conversion definition creating method of the present invention relates to, for example, a target device such as a printing press and an output device such as a printer, such as “output device profile: correspondence between restricted coordinates and colorimetric coordinates on the output device color space” and “ Target profile: “correspondence between target coordinates and colorimetric coordinates” is acquired. Further, with reference to the colorimetric coordinates associated with the target coordinates of the target in the target profile, the colorimetric coordinates associated with the restriction coordinates in the output device profile out of the restricted coordinates in the output device color space are the reference. A closer one is searched, and the target coordinates of the target are associated with the limited coordinates that are the search results. By associating the target coordinates and the limit coordinates that make the corresponding colorimetric coordinates closer, using the device-independent colorimetric coordinates as a medium, the target coordinates represent the color that is close to the color that the target coordinates represent, In addition, it is possible to create a color conversion definition that converts the total amount of ink to be overlaid when outputting an image into restricted coordinates with a restricted amount.
[0012]
Further, in the color conversion definition creating method of the present invention, the correspondence acquisition process described above is output by the output device based on the chart data defined by the limit coordinates representing the color chart in which a plurality of color patches are arranged. It may be a process of obtaining the correspondence between the restriction coordinates and the colorimetric coordinates obtained by measuring the color patches of the color chart.
[0013]
In the color conversion definition creating method of the present invention, the coordinate search process described above applies the target coordinates of each of a plurality of predetermined points on the target color space as target target coordinates, and the limited coordinates for each target coordinate of each target. Is the process of exploring
A correspondence estimation process for estimating the correspondence between the target coordinates and the restriction coordinates of points other than the predetermined plural points based on the correspondence between the target coordinates and the restriction coordinates of the predetermined plural points obtained in the color conversion definition creation process. It is preferable to have a process.
[0014]
Conventionally, when expressing the color by overlaying the inks, if the total amount of ink exceeds the limit value, the amount of ink to be superimposed is reduced by reducing the amount of each ink forming the color as a whole. Limiting the total amount is being done. However, according to this method, the portion where the total amount of ink exceeds the limit value is clearly separated from the portion where the ink amount is reduced and the portion where the ink amount is not decreased. There is a problem that the color gradation becomes discontinuous in the vicinity.
[0015]
According to the above preferred form of the color conversion definition creating method of the present invention, search is made for limited coordinates that represent colors close to the color represented by the target coordinates, which are associated with a plurality of target coordinates on the target color space. After that, based on the correspondence, the limit coordinates associated with the target coordinates of points other than the predetermined plural points are estimated. For example, searching for correspondence that faithfully reproduces representative colors such as primary colors and secondary colors that are important in printing is first searched, and correspondence in other colors is calculated by interpolation calculation or the like. Create a color conversion definition that converts the important colors to the desired color and other colors gradually change from the important colors to maintain the continuity of the color gradation. be able to.
[0016]
In the color conversion definition creating method of the present invention, the output device color space is a color space having coordinate axes corresponding to cyan, magenta, yellow, and black,
The coordinate search process may be performed by fixing each component of cyan, magenta, and yellow of the restricted coordinates in the correspondence acquired in the correspondence acquisition process and changing only the black component.
[0017]
By fixing the cyan, magenta, and yellow components of the limit coordinates and performing the search while changing only the black component, it is possible to limit the total amount of ink while retaining the color.
[0018]
In the color conversion definition creating method of the present invention, it is preferable that the coordinate search process applies a plurality of points on the boundary of the color reproduction region of the target device as the predetermined plurality of points.
[0019]
On the boundary of the color reproduction region, colors that are regarded as important in printing, such as primary colors and pure colors of secondary colors, are included, and the correspondence in these colors is not estimated in the correspondence estimation process. In the coordinate search process, it is preferable to search for a correspondence that performs faithful color reproduction.
[0020]
In the color conversion definition creating method of the present invention, the coordinate search process described above applies a plurality of points on the boundary of the color reproduction region of the target device as the predetermined plurality of points.
The correspondence estimation process is preferably a process using interpolation as an estimation.
[0021]
By using interpolation as the estimation, the correspondence can be estimated with high accuracy.
[0022]
The color conversion definition creating apparatus of the present invention also includes target coordinates on a target color space depending on a target device that outputs an image based on image data, and a proof image that reproduces the target image when the image is obtained by the target device. Creates a color conversion definition that represents the correspondence with the limit coordinates that exist in the output device color space that depends on the output device that outputs based on the image data, and the sum of the coordinate components that make up the coordinates is limited to a predetermined limit value or less. In the color conversion definition creation device
A correspondence acquisition unit that acquires a correspondence relationship between the limit coordinates and the colorimetric coordinates in the device-independent colorimetric color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, the correspondence is within the limit coordinate range associated with the colorimetric coordinates by the correspondence acquired by the correspondence acquisition unit. A coordinate search unit for searching for a limit coordinate whose colorimetric coordinate is closer to the reference;
A color conversion definition creating unit that creates a color conversion definition by associating target coordinates with restricted coordinates searched by the coordinate search unit is provided.
[0023]
It should be noted that the color conversion definition creating apparatus of the present invention includes all various aspects corresponding to various aspects of the color conversion definition creating method of the present invention.
[0024]
The color conversion definition creating program of the present invention is executed in a computer, and the target coordinates on the target color space depending on the target device that outputs an image based on the image data by the computer, and the image on the target device. A restriction that exists in the output device color space that depends on the output device that outputs the proof image that reproduces the target image at the time of acquisition based on the image data, and the sum of the coordinate components constituting the coordinates is limited to a predetermined limit value or less. In the color conversion definition creation program that creates a color conversion definition that represents the correspondence with coordinates,
A correspondence acquisition unit that acquires a correspondence relationship between the restriction coordinates and the colorimetric coordinates on the device-independent colorimetric color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, within the range of the limited coordinates associated with the colorimetric coordinates by the correspondence acquired by the correspondence acquisition unit, A coordinate search unit for searching for a limited coordinate whose corresponding colorimetric coordinate is closer to the reference;
A color conversion definition creating unit that creates a color conversion definition by associating the target coordinates with the limited coordinates searched by the coordinate search unit is provided.
[0025]
By executing the color conversion definition creating program of the present invention in a computer, the computer can be operated as the color conversion definition creating apparatus as described above.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0027]
FIG. 1 is an overall configuration diagram of a printing and proof image creation system to which an embodiment of the present invention is applied.
[0028]
The color scanner 10 reads the original image 11 and generates CMYK four-color color separation image data representing the read original image 11. The CMYK image data is input to the workstation 20. In the workstation 20, electronic plate collection based on the input image data is performed by the operator, and image data representing an image for printing is generated. The image data for printing is input to the film printer 30 when printing is performed, and the film printer 30 creates CMYK printing film originals corresponding to the input image data.
[0029]
A printing plate is created from the printing film original plate, and the created printing plate is mounted on the printing machine 40. Ink is applied to the printing plate mounted on the printing machine 40, and the applied ink is transferred onto a printing sheet to form a printed image 41 on the sheet.
[0030]
A series of operations in which a film original plate is prepared by the film printer 30, a printing plate is further prepared and mounted on the printing machine 40, ink is applied to the printing plate and printing is performed on paper is a large-scale operation. Cost too. For this reason, before the actual printing operation is performed, the proof image 61 is created by the printer 60 as follows, and the finished confirmation of the printed image 41 is performed in advance.
[0031]
In creating a proof image, image data created by electronic plate collection on the workstation 20 is input to the personal computer 50. Here, the image data input to the personal computer 50 is language data described in so-called PDL (Page Description Language), or image data (hereinafter referred to as halftone dot area ratio) that is compatible with the printer 40. In the personal computer 50, the CMYK four colors adapted to the printer 60 and developed into a bitmap by the so-called RIP (Raster Image Processor) 100 are used in the personal computer 50. Converted to image data. The CMYK four-color image data is substantially the same as the image data for printing input to the film printer 30. Here, the function of the RIP 100 will be described.
[0032]
The RIP 100 includes functions as a color correction device 110, a color conversion device 120 to which an embodiment of the color conversion definition creation device of the present invention is applied, and an image development device 130, respectively.
[0033]
In the example shown here, in the color conversion device 120 of the RIP 100, the image data for printing that has passed through the page description data expansion device 140 and the color correction device 110 is adapted to the color space of the printer 60, and an image based on the image data is displayed. Conversion to image data in which the total amount of ink to be overlaid when output by the printer 60 is limited (hereinafter, image data in which the amount of ink is limited is referred to as limited image data) is performed. A color conversion profile 200 having a LUT (Look Up Table) format that is referred to when converting image data is created. A method for creating and using the color conversion profile 200 will be described later. Here, for convenience of explanation, in the present embodiment, the color space of the printer 60 is described as being a CMYK color space. Hereinafter, the CMYK color space suitable for the printing machine 40 is adapted to the print color space, the printer 60. The CMYK color space is referred to as a printer color space. The colorimeter 70 shown in FIG. 1 relates to the creation of the color conversion profile 200.
[0034]
When print image data is sent from the workstation 20 to the personal computer 50, the page description data expansion device 140 displays the print image data when the print image data is page description data. Expands to halftone data defined by the halftone dot area ratio. Further, the page description data expansion device 140 sends the print image data converted into halftone data to the color correction device 110, and when the sent print image data is originally halftone data. Sends the image data for printing to the color correction device 110 as it is. The color correction device 110 converts, for example, the gradation of the color of the image into the image data sent from the page description data development device 140, for correcting the color of the image represented by the image data to a preferable color in printing. Image correction processing such as tone conversion processing is performed. When the image data subjected to the image correction processing is directly converted into image data in a printer color space suitable for the printer 60, and a proof image based on the converted image data is output by the printer 60, the image data in the proof image is displayed. Depending on the color portion, a large amount of ink is expressed in a superimposed manner, so that the ink may be peeled off. In order to avoid this, the image data subjected to the image correction processing is sent to the color conversion device 120, and the color conversion profile 120 is referred to by the color conversion device 120, and the image data is overlapped in the printer color space. It is converted into restricted image data in which the amount of ink is restricted. The restricted image data is halftone data, and cannot be output by the printer 60 as it is. Therefore, the restricted image data is sent to the image developing device 130, and is converted into bitmap restricted image data that can be output by the printer 60. The limited image data in the bitmap format after the conversion is input to the printer 60, and the printer 60 creates a proof image 61 based on the input limited image data.
[0035]
By creating the proof image 61 in this way and confirming the proof image 61, it is possible to confirm the print finish in advance. The printer 40 shown in FIG. 1 corresponds to an example of a target device according to the present invention, and the printer 60 corresponds to an example of an output device according to the present invention. The print color space (CMYK color space) suitable for the printing machine 40 is an example of the target color space according to the present invention, and the printer color space (CMYK color space) suitable for the printer 60 is an example of the printer color space according to the present invention. It corresponds to.
[0036]
Here, the hardware of the personal computer 50 provided with the RIP 100 will be described.
[0037]
2 is an external perspective view of the colorimeter 70 and the personal computer 50 shown in FIG. 1, and FIG. 3 is a hardware configuration diagram of the personal computer 50. As shown in FIG.
[0038]
2 is mounted with a color chart 90 in which a plurality of color patches are arranged as shown in FIG. 4, and a plurality of color patches 91a, 91b,. A colorimetric value (here, XYZ value) is measured for each of the above. Colorimetric data representing the colorimetric values of each color patch obtained by the measurement by the colorimeter 70 is input to the personal computer 50 via the cable 92.
[0039]
The color chart 90 is created by printing with the printing machine 40 shown in FIG. 1 or by printing with the printer 60. The personal computer 50 corresponds to each color patch constituting the color chart 90. The personal computer 50 knows the color data (CMYK values) to be converted, and performs color conversion based on the color data of each color patch of the color chart 90 and the colorimetric data obtained by the colorimeter 70. A profile 200 is created. Detailed explanation regarding this point will be described later. Here, the hardware configuration of the personal computer 50 will be described next.
[0040]
The personal computer 50 has an appearance configuration, the main body device 51, an image display device 52 that displays an image on a display screen 52a in accordance with an instruction from the main body device 51, and a main body device 51 that can perform various operations according to key operations. A keyboard 53 for inputting information and a mouse 54 for inputting an instruction corresponding to, for example, an icon or the like displayed at that position by designating an arbitrary position on the display screen 52a are provided. The main body device 51 has an FD loading port 51a for loading a flexible disk (hereinafter abbreviated as FD) and a CD-ROM loading port 51b for loading a CD-ROM.
[0041]
As shown in FIG. 3, the main unit 51 includes a CPU 511 that executes various programs, a main memory 512 that is read for execution by the CPU 511, and a program stored in the hard disk device 513. And a hard disk device 513 storing data and the like, an FD drive 514 accessing the FD 520, and a CD-ROM 521 are loaded, connected to the CD-ROM drive 515 accessing the loaded CD-ROM 521, and the colorimeter 70, An I / O interface 516 that receives colorimetric data from the colorimeter 70 is built in, and these various elements and the image display device 52, keyboard 53, and mouse 54 shown in FIG. Are connected to each other.
[0042]
Here, a color conversion program for operating the personal computer 50 as the color conversion device 120 of FIG. 1 is stored in the CD-ROM 521 to which one embodiment of the color conversion definition creation program of the present invention is applied. The CD-ROM 521 is loaded into the CD-ROM drive 515, and the color conversion program stored in the CD-ROM 521 is uploaded to the personal computer 50 and stored in the hard disk device 513. When this color conversion program is started and executed, the personal computer 50 creates a color conversion definition for converting image data into restricted image data in accordance with a color conversion definition creation method described later. It operates as the color conversion device 120 to which one embodiment of the color conversion definition creation device of the present invention that converts image data into restricted image data using the color conversion definition is applied.
[0043]
Next, a color conversion program for generating the color conversion apparatus 120 of FIG. 1 to which an embodiment of the present invention is applied will be described.
[0044]
FIG. 5 is a conceptual diagram showing a CD-ROM 521 in which an embodiment of the color conversion definition creating program of the present invention is stored.
[0045]
The color conversion program 530 stored in the CD-ROM 521 includes a correspondence acquisition unit 531, a coordinate search unit 532, a correspondence estimation unit 533, a color conversion definition creation unit 534, and an image data conversion unit 535. Here, the correspondence acquisition unit 531 corresponds to an example of a correspondence acquisition unit in the color conversion definition creation program of the present invention. Similarly, the coordinate search unit 532 corresponds to an example of a coordinate search unit, and the correspondence estimation unit 533 corresponds to a correspondence estimation. The color conversion definition creation unit 534 corresponds to an example of a color conversion definition creation unit. Details of each part of the color conversion program 530 will be described together with the operation of each part of the color conversion apparatus 120 to which one embodiment of the color conversion definition creating apparatus of the present invention shown in FIGS. 1 and 6 is applied.
[0046]
FIG. 6 is a functional block diagram of the color conversion device 120 when the color conversion program 530 is installed in the personal computer 50 of FIG. 2 and the personal computer 50 is operated as an embodiment of the color conversion definition creation device of the present invention. is there. Below, the component of the color converter 120 and the rough effect | action by those components are demonstrated.
[0047]
The color conversion apparatus 120 also illustrated in FIG. 1 includes a correspondence acquisition unit 121, a coordinate search unit 122, a correspondence estimation unit 123, a color conversion definition creation unit 124, and an image data conversion unit 125. When the color conversion program 530 shown in FIG. 5 is installed in the personal computer 50 shown in FIGS. 1 to 3, the correspondence acquisition unit 531 of the color conversion program 530 constitutes the correspondence acquisition unit 121 of FIG. Reference numeral 532 constitutes a coordinate search unit 122, correspondence estimation unit 533 constitutes a correspondence estimation unit 123, color conversion definition creation unit 534 constitutes a color conversion definition creation unit 124, and image data conversion unit 535 represents an image data conversion unit. 125 is configured.
[0048]
The correspondence acquisition unit 121, the coordinate search unit 122, the correspondence estimation unit 123, and the color conversion definition creation unit 124 in FIG. 6 are adapted to the image data in the print color space suitable for the printing machine 40 in FIG. This is an element for creating a color conversion profile 200 representing the correspondence with restricted image data in the printer color space.
[0049]
The correspondence acquisition unit 121 includes a print profile representing a correspondence between image data on the print color space and image data on a device-independent colorimetric color space (hereinafter described using an XYZ color space as the colorimetric color space), and Then, a printer restriction profile representing the correspondence between the restricted image data on the printer color space and the image data on the colorimetric color space is created. A method for creating each profile will be described later. The correspondence acquisition unit 121 corresponds to an example of a correspondence acquisition unit in the color conversion definition creation apparatus of the present invention.
[0050]
The coordinate search unit 122 receives a print profile and a printer restriction profile from the correspondence acquisition unit 121. First, the coordinate search unit 122, among the image data of the print color space in the print profile, a plurality of predetermined image data (target data) and the image data (reference data) of the colorimetric color space corresponding to each of the target data. ) To get. Further, search is made for the image data in the corresponding colorimetric color space that is closest to each reference data among the restricted image data in the printer restriction profile. The coordinate search unit 122 corresponds to an example of a coordinate search unit in the color conversion definition creating apparatus of the present invention. A combination of a plurality of predetermined image data (target data) in the print color space and the restricted image data searched for each target data is sent to the color conversion definition creating unit 124.
[0051]
The correspondence estimation unit 123 receives a plurality of predetermined image data (target data) in the print color space from the color conversion definition creation unit 124, and the limited image data searched by the coordinate search unit 122 for each target data. Based on these combinations, a combination of image data other than a plurality of predetermined image data and limited image data corresponding to the image data is estimated based on the combination. . The correspondence estimation unit 123 corresponds to an example of a correspondence estimation unit in the color conversion definition creation apparatus of the present invention. The estimated combination of the print color space image data and the restricted image data is sent to the color conversion definition creation unit 124.
[0052]
When a combination of a plurality of predetermined image data (target data) in the print color space and the limited image data searched for each target data is sent from the coordinate search unit 122, a color conversion definition creation unit 124 sends the combination to the correspondence estimation unit 123. When a combination of image data other than a plurality of predetermined image data and restricted image data is sent from the correspondence estimation unit 123 among the image data in the print color space, the color conversion definition creation unit 124 further The color conversion table 200 is created by associating the image data on the print color space with the restricted image data for all the combinations that have been sent. The color conversion definition creating unit 124 corresponds to an example of a color conversion definition creating unit in the color conversion definition creating apparatus of the present invention. The created color conversion table 200 is sent to the image data conversion unit 125.
[0053]
The image data conversion unit 125 uses the color conversion profile 200 created by the color conversion definition creation unit 124 to output image data in the print color space sent from the color correction device 110 in the RIP 100 shown in FIG. Convert to restricted image data in the printer color space. The converted restricted image data is sent to the image developing device 130 shown in FIG.
[0054]
The color conversion device 120 is basically configured as described above.
[0055]
FIG. 7 is a flowchart showing a series of processing performed by the RIP 100. In the following, a series of processes for creating the proof image 61 will be described in detail with reference to the flowchart of FIG.
[0056]
In the RIP 100, as a step before creating the proof image 61, the color conversion profile 200 referred to by the image data conversion unit 125 in FIG. 6 is created (step S1 in FIG. 7).
[0057]
FIG. 8 is a flowchart showing an embodiment of the color conversion definition creating method of the present invention. Here, the description of the flowchart of FIG. 7 is interrupted, and a series of processes for creating the color conversion profile 200 by applying one embodiment of the color conversion definition creating method of the present invention will be described according to the flowchart of FIG. For convenience of explanation, the following description will be made assuming that the total amount of ink to be overlapped is limited to a value up to the limit amount S. This limit amount S corresponds to an example of a predetermined limit value referred to in the present invention.
[0058]
In step T1 in FIG. 8, first, the correspondence acquisition unit 121 in FIG. 6 generates a print profile in which coordinates in the print color space are associated with coordinates in the colorimetric color space.
[0059]
The workstation 20 shown in FIG. 1 generates halftone data for CMYK profile creation that is sequentially changed to 0%, 10%,..., 100%, for example, in accordance with the print color space (CMYK color space). In accordance with the printing procedure described above, a color chart 90 (see FIG. 4) based on the halftone data thus generated is created. The print image 41 shown in FIG. 1 is not a diagram showing a color chart, but it is assumed that the color chart 90 shown in FIG. 4 is printed instead of the print image 41, and each color patch 91a constituting the color chart is printed. , 91b,... Are measured by the colorimeter 70. By doing so, a print profile representing the correspondence between the coordinates on the print color space and the coordinates on the colorimetric color space is constructed.
[0060]
FIG. 9 is a conceptual diagram of a print profile.
[0061]
In this print profile, image data defined in CMYK is input, and the image data is converted into image data defined in XYZ. A print profile for converting the image data defined by CMYK into image data defined by XYZ is represented by T. The print profile T corresponds to an example of “predetermined correspondence between target coordinates and colorimetric coordinates” according to the present invention.
[0062]
When the print profile T is generated, in step T2 in FIG. 8, the correspondence acquisition unit 121 uses coordinates in which the total sum of coordinate components in the printer color space is limited to a value up to the limit amount S (hereinafter referred to as the limited image data). A printer restriction profile in which coordinates that are defined and whose coordinates are restricted is referred to as restriction coordinates) and coordinates in the colorimetric color space are generated.
[0063]
This printer restriction profile creation method creates a print profile T except that the output device for outputting the color chart is a printer, not a printing press, and that the network data for profile creation is restricted image data. It is the same as the method.
[0064]
First, halftone data in the printer color space in which the sum of the components corresponding to each color is limited to the limit amount S is prepared.
[0065]
In the personal computer 50 shown in FIG. 1, a series of network% for creating a CMYK profile in which each color is sequentially changed to, for example, 0%, 10%,..., 100% in accordance with the printer color space (CMYK color space). Generate data. Further, the sum of the components corresponding to the four colors of CMYK corresponding to the total amount of ink is calculated for each halftone data. Here, for example, the components corresponding to each color of CMYK in the i-th half% data for profile creation are (C, M, Y, K) = (C_i, M_i, Y_i, K_i), The total amount of ink Ink at this time_iIs
Total ink amount Ink_i= C_i+ M_i+ Y_i+ K_i
Is calculated by This ink total amount Ink_iIs larger than the limit amount S, the ink total amount Ink_iConversion coefficient R when the value is reduced to a value less than the limit amount S_iThe
Conversion factor R_i= S / Ink_i
It is calculated by the formula of At this time, the i-th network% data (C, M, Y, K) for profile creation of CMYK = (C_i, M_i, Y_i, K_i) Corresponding to halftone data (C ′) in which the sum of the components of each color is limited to the limit value S_i, M ’_i, Y ’_i, K ’_i) Is the total ink amount Ink_iIn the case of the limit amount S,
(C ’_i, M ’_i, Y ’_i, K ’_i) = (C_i, M_i, Y_i, K_i)
Total ink amount Ink_i> If the limit amount is S,
(C ’_i, M ’_i, Y ’_i, K ’_i) = (R_i× C_i, R_i× M_i, R_i× Y_i, K_i)
It is calculated by the following formula. By the procedure as described above, halftone data corresponding to each of a series of halftone data for profile creation, each of which is limited in the sum of the components of each color, is calculated.
[0066]
When a series of halftone data in which the sum of the components of each color is limited is prepared, the halftone data is then sent to the printer 60, and the printer 60 prints a color chart based on the halftone data. The
[0067]
The proof image 61 shown in FIG. 1 is not an image representing a color chart. However, in the printer 60, for example, the proof image 61 is created by printing on the printing machine 40 to create a printing profile instead of the proof image 61. A color chart of the same type as that of the color chart is output, and each color patch constituting the color chart is measured by the colorimeter 70. By doing so, a printer restriction profile that represents the correspondence between the restriction coordinates on the printer color space and the coordinates on the colorimetric color space (XYZ space) for the printer 60 is constructed.
[0068]
FIG. 10 is a conceptual diagram of a printer restriction profile.
[0069]
Restricted image data defined in CMYK is input to the printer restriction profile, and the restricted image data in CMYK is converted into XYZ colorimetric data. Here, P represents a printer restriction profile for converting the CMYK restricted image data into XYZ colorimetric data. The printer restriction profile P is an example of “correspondence between restriction coordinates and colorimetric coordinates” according to the present invention, and the process of step T2 for generating the printer restriction profile P is a correspondence acquisition in the color conversion definition creating method of the present invention. It corresponds to an example of the process. The generated print profile T and printer restriction profile P are sent to the coordinate search unit 122 from the correspondence acquisition unit 121 of FIG.
[0070]
It should be noted that the halftone data may be sequentially changed at intervals other than 10%. Here, the printer 60 is described as a printer that outputs an image based on CMYK image data. However, for example, a printer that outputs an image based on RGB image data also includes RGB colors in the personal computer 50. By generating profile data defined in space and outputting a color chart, a printer restriction profile suitable for the printer can be created in the same manner. However, here, a description will be given assuming that the printer 60 that outputs an image based on CMYK image data is used.
[0071]
When the print profile T and the printer restriction profile P are generated, in step T3 in FIG. 8, the coordinate search unit 122 in FIG. 6 uses the color closest to each color represented by a plurality of predetermined coordinates in the print color space in the print profile T. Representing the restriction coordinates of the printer color space in the printer restriction profile P.
[0072]
Before searching for the limited coordinates, first, K is set for each of the coordinates of all the print color spaces constituting the print profile T (correspondence between CMYK of the print color space and XYZ of the colorimetric color space) generated by the correspondence acquisition unit 121. A cubic CMY color space having the components fixed and having the CMY3 component as a variable is obtained. The set of CMY color spaces obtained in this way is equivalent to the print color space.
[0073]
FIG. 11 is a diagram illustrating a series of color spaces in which the K component is fixed to each coordinate of the print color space in the print profile T.
[0074]
FIG. 11 shows a cubic CMY color space 600 in which the K component of the coordinates of the printing color space in the printing profile T is fixed to a series of values of 0%, 10%,..., 100%. Yes. FIG. 11 also shows grid points E in which the coordinates of the print color space in the print profile T are set in a grid pattern on each CMY color space 600.
[0075]
Subsequently, a plurality of predetermined coordinates in the print color space are acquired. In this embodiment, the value of the K component is K as a plurality of coordinates._iEight vertices D in each of the CMY color spaces 600 when (i = 0, 10,... 100)_jThe coordinates of (j = 0, 1,... 7) are acquired. Each vertex D_jCorresponds to an example of a predetermined plurality of points according to the present invention.
[0076]
8 vertices D_jWhen the coordinates are acquired, the limit coordinates are searched. That is, each vertex D_jCoordinates (C_Dj, M_Dj, Y_Dj, K_i) As the target coordinates, the colorimetric coordinates (X_Dj, Y_Dj, Z_Dj) As reference coordinates, among the restriction coordinates of the printer color space in the printer restriction profile P, the ones whose colorimetric coordinates corresponding to the restriction coordinates are closest to the reference coordinates are respectively searched. The search procedure in this embodiment is shown below.
[0077]
First, in the same manner as when the printer image color space limited image data corresponding to the halftone data of the printer color space is calculated in step T2 in FIG. 8, the print color space limit coordinates (target limit) respectively corresponding to each target coordinate. (Referred to as coordinates). Target coordinates (C_Dj, M_Dj, Y_Dj, K_i) Target restriction coordinates (C ')_Dj, M ’_Dj, Y ’_Dj, K ’_i)
Total ink amount Ink_{i_j}= C_Dj+ M_Dj+ Y_Dj+ K_i
Conversion factor R_{i_j}= S / Ink_{i_j}
The total amount of ink Ink depends on whether the total amount of ink calculated in_{i_j}In the case of the limit amount S,
Target limit coordinates (C '_Dj, M ’_Dj, Y ’_Dj, K ’_i) = (C_Dj, M_Dj, Y_Dj, K_i)
Total ink amount Ink_{i_j}> If the limit amount is S,
Target limit coordinates (C '_Dj, M ’_Dj, Y ’_Dj, K ’_i) = (R_{i_j}× C_Dj, R_{i_j}× M_Dj, R_{i_j}× Y_Dj, K_i)
Is calculated by
[0078]
Subsequently, target limit coordinates (C ′_Dj, M ’_Dj, Y ’_Dj, K ’_i) And the coordinate values of the printer color space in the printer restriction profile P having the same value for each coordinate component (C ′)_P, M ’_P, Y ’_P, K ’_P), That is,
Restricted coordinates of the printer color space (C '_P, M ’_P, Y ’_P, K ’_P) = Target limit coordinate (C ′)_Dj, M ’_Dj, Y ’_Dj, K ’_i)
Get the limit coordinates of the printer color space. Furthermore, the reference coordinates (X_Dj, Y_Dj, Z_Dj) And the coordinate coordinates closest to the coordinate component are the limit coordinates (C ′) of the printer color space in the printer limit profile P._P, M ’_P, Y ’_P, K ’_P) And the corresponding colorimetric coordinates (X_P, Y_P, Z_P) To obtain the limit coordinates of the printer color space corresponding to the searched colorimetric coordinates. A combination of the target coordinates and the acquired limit coordinates of the printer color space is sent from the coordinate search unit 122 of FIG. 6 to the color conversion definition creation unit 124. This reference coordinate corresponds to an example of the reference referred to in the present invention. Further, a series of processing until obtaining the restriction coordinates of the printer color space combined with the target coordinates shown in Step T3 in FIG. 8 corresponds to an example of a coordinate search process in the color conversion definition creating method of the present invention.
[0079]
Here, in the present embodiment, the printer color space (CMYK) is a color space having coordinate axes corresponding to the same CMYK four colors as the print color space (CMYK), and therefore, target restriction coordinates corresponding to the target coordinates are calculated, By searching for the limit coordinates close to the limit coordinates of the printer color space whose coordinate components are the same as the target limit coordinates, the search range was narrowed to speed up the processing. It is also possible to perform a search for all restriction coordinates in the printer restriction profile P without calculating. In addition, when the range of colorimetric coordinate values (color reproduction area) in the print profile T and the range of colorimetric coordinate values (color reproduction area) in the printer restriction profile P are greatly different, before searching for the restriction coordinates, Conversion processing for matching the respective color reproduction regions may be performed.
[0080]
From the coordinate search unit 122, a plurality of predetermined points in the print profile T (each vertex D among the grid points E on each CMY color space 600)._j) Coordinates (C_Dj, M_Dj, Y_Dj, K_i) And restriction coordinates (C ′) in the printer restriction profile P_P, M ’_P, Y ’_P, K ’_P) Is sent, the color conversion definition creation unit 124 sends the combination to the correspondence estimation unit 123.
[0081]
In step T4 of FIG. 8, the correspondence estimation unit 123 uses a point other than a predetermined plurality of points in the print profile T (vertex D of lattice points E on each CMY color space 600)._jCoordinates (C) of other grid points E)_any, M_any, Y_any, K_i) (Any: each vertex D_jLimit coordinate (C ′) in the printer color space combined with a grid point E) other than_{P_any}, M ’_{P_any}, Y ’_{P_any}, K ’_{P_any}) Is calculated. In the present embodiment, eight vertices D in each CMY color space 600 are used._jAmong them, a four-point interpolation method in which four points surrounding the lattice point E are selected and weighted is adopted, and the limit coordinates on the printer color space combined with the coordinates of the lattice point E are calculated. Hereinafter, a procedure for calculating the limit coordinates on the printer color space by the four-point interpolation method will be described.
[0082]
First, the coordinates of each grid point E (C_any, M_any, Y_any, K_i), The eight vertices D_j4 points to be weighted are selected. For example, the coordinate component of the grid point E is Y_any<M_any<C_anyThen point D₀And point D₇In addition to point D₁And point D_ThreeSelect
Coordinate₀= Vertex D₀Restricted coordinates in the printer color space combined with the coordinates of
Coordinate₀= Vertex D₇Restricted coordinates in the printer color space combined with the coordinates of
Coordinate_a= Vertex D₁Restricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D_ThreeRestricted coordinates in the printer color space combined with the coordinates of
Four vertices D_jThe interpolation calculation is performed using the limited coordinates of the printer color space combined with the coordinates of. At this time, Y_any<M_any<C_anyTherefore, for example, the coordinate component of the lattice point E is Y_any<M_any<C_anyThen vertex D₀And vertex D₇In addition to vertex D₁And vertex D_ThreeIs selected, and interpolation calculation is performed using the coordinates of these four points. At this time, Y_any<M_any<C_anySo
V_L= C_any
V_M= M_any
V_S= Y_any
And the weighting coefficient when performing interpolation calculation,
K₀= 1-V_L
K₇= V_S
K_a= V_L-V_M
K_b= V_M-V_S
And the limit coordinates on the printer color space combined with the coordinates of the grid point E are
Restricted coordinates on printer color space = K₀·Coordinate₀+ K₇·Coordinate₀+ K_a·Coordinate_a+ K_b·Coordinate_b
It is calculated by the interpolation formula. Hereinafter, similarly, the coordinate component of the lattice point E is M_any<Y_any<C_anyThen vertex D₀And vertex D₇In addition to vertex D₁And vertex D_FiveSelect the above coordinates_a,Coordinate_b, V_L, V_M, V_SInstead of
Coordinate_a= Vertex D₁Restricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D₆Restricted coordinates in the printer color space combined with the coordinates of
V_L= C_any
V_M= Y_any
V_S= M_any
To get the value Y_any<C_any<M_anyThen vertex D₀And vertex D₇In addition to vertex D₂And vertex D_ThreeSelect
Coordinate_a= Vertex D₂Restricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D_ThreeRestricted coordinates in the printer color space combined with the coordinates of
V_L= M_any
V_M= C_any
V_S= Y_any
To get the value C_any<Y_any<M_anyThen vertex D₀And vertex D₇In addition to vertex D₂And vertex D₆Select
Coordinate_a= Vertex D₂Restricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D₆Restricted coordinates in the printer color space combined with the coordinates of
V_L= M_any
V_M= Y_any
V_S= C_any
To get the value M_any<C_any<Y_anyThen vertex D₀And vertex D₇In addition to vertex D_FourAnd vertex D_FiveSelect
Coordinate_a= Vertex D_FourRestricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D_FiveRestricted coordinates in the printer color space combined with the coordinates of
V_L= Y_any
V_M= C_any
V_S= M_any
To get the value C_any<M_any<Y_anyThen vertex D₀And vertex D₇In addition to vertex D_FourAnd vertex D₆Select
Coordinate_a= Vertex D_FourRestricted coordinates in the printer color space combined with the coordinates of
Coordinate_b= Vertex D₆Restricted coordinates in the printer color space combined with the coordinates of
V_L= Y_any
V_M= M_any
V_S= C_any
To get the value Then, these values are substituted into the formula for calculating the “restricted coordinates in the printer color space”. In this embodiment, a four-point interpolation method is employed in which four of the conversion coefficients at eight vertices are selected and weighted, but the limited coordinates on the printer color space combined with the coordinates of the grid point E are as follows: In addition, it is also possible to calculate by interpolating with a 6-point interpolation method, an 8-point interpolation method, or the like. Furthermore, the limit coordinates on the printer color space may be estimated by a method other than interpolation. Each vertex D of each CMY color space 600 in step T3 in FIG._jThe process of calculating the limit coordinates on the printer color space combined with the coordinates of the grid point E other than the above corresponds to an example of the correspondence estimation process in the color conversion definition creating method of the present invention.
[0083]
Vertex D on each CMY color space 600 shown in FIG._jWhen the combination of the target coordinates at all grid points E including the limit coordinates of the printer color space is calculated, in step T5 in FIG. 8, the color conversion definition creating unit 124 in FIG. The color conversion profile 200 is generated by associating the limit coordinates of the printer color space.
[0084]
FIG. 12 is a conceptual diagram of the color conversion profile 200.
[0085]
CMYK image data for printing is input to the color conversion profile 200, and the image data is converted into CMYK restricted image data for a printer. The color conversion profile 200 created in the above procedure is sent from the color conversion definition creation unit 124 to the image data conversion unit 125. The color conversion profile 200 corresponds to an example of the color conversion definition referred to in the present invention, and the process of step T5 in FIG. 8 for creating the color conversion profile 200 is a color conversion definition creating process in the color conversion definition creating method of the present invention. It corresponds to an example.
[0086]
Returning to the flowchart of FIG.
[0087]
The color correction apparatus 110 shown in FIG. 1 acquires image data for printing from the workstation 20 (step S2 in FIG. 7). The color correction device 110 performs an image correction process on the acquired image data to correct the color of the image represented by the image data to a color preferable for printing (step S3 in FIG. 7), and the image data after the image correction process is processed. And sent to the image data converter 125 shown in FIG.
[0088]
The image data conversion unit 125 refers to the color conversion profile 200 created in advance in step S1 of FIG. 7, and the image data of the print color space sent from the color correction device 110 of FIG. The image data is converted into limited image data in which the total amount of ink is limited (step S4 in FIG. 7).
[0089]
The converted restricted image data is sent from the image data conversion unit 125 to the image expansion device 130 in FIG. 1 and converted into image data in the bitmap format (step S5 in FIG. 7). The bitmap format image data is sent to the printer 60, and a proof image 61 is generated in the printer 60 (step S6 in FIG. 7). In this proof image, the amount of ink to be overlaid is limited, and the occurrence rate of defects such as film peeling is suppressed. The image data sent from the color correction device 110 to the color conversion device 120 is converted into restricted image data based on a color conversion profile 200 created using a series of conversion coefficients calculated by interpolation calculation. Therefore, the continuity of the color gradation is maintained. Further, the color conversion profile 200 that is referred to when converting the image data in the print color space to the restricted image data in the printer color space is a color that is as close as possible to the color represented by the image data in the print color space through the colorimetric color space. Therefore, even if the color of the ink overlaid by the printer 60 is limited, a proof image 61 having the same color as the printed image 41 can be obtained. .
[0090]
Above, description of 1st Embodiment of this invention is complete | finished, Next, 2nd Embodiment of this invention is described. The second embodiment has the same configuration as that of the color conversion device 120 of the first embodiment shown in FIG. 6, but the coordinate search method performed by the coordinate search unit is different. Further, since the second embodiment is different from the first embodiment only in the process of step T3 in the flowchart of FIG. 8, hereinafter, the second embodiment is applied mainly to the process of step T3, and the color conversion profile is applied. The procedure for creating a file will be described.
[0091]
Also in the second embodiment, as in the first embodiment, first, in the correspondence acquisition unit in FIG. 6, the print profile in which the coordinates of the print color space (CMYK) and the coordinates of the colorimetric color space (XYZ) are associated with each other. A printer restriction profile P in which T and the restriction coordinates of the printer color space (CMYK) are associated with the coordinates of the colorimetric color space (XYZ) is generated (steps S1 and S2 in FIG. 8).
[0092]
When the print profile T and the printer restriction profile P are generated, in step T3 in FIG. 8, the coordinate search unit in FIG. 6 searches for the restriction coordinates. In the second embodiment, the restriction coordinate search condition in the first embodiment “the printer color in the printer restriction profile P that represents a color closer to the color represented by the coordinates of a predetermined plurality of points in the print color space in the print profile T. In addition to “restricted coordinates in space”, restricted coordinates that satisfy the condition “restricted coordinates in printer color space having a large chromaticity value” are searched.
[0093]
As in the first embodiment, before searching for the limited coordinates, first, each of the components in FIG. 11 using CMY3 colors as variables, in which K components are fixed to all the coordinates of the print color space constituting the print profile T. A CMY color space 600 is determined.
[0094]
Subsequently, as in the first embodiment, eight vertices D of each CMY color space 600 are used as the coordinates of a predetermined plurality of points in the print color space._jCoordinates (C_Dj, M_Dj, Y_Dj, K_i) Is acquired.
[0095]
Vertex D_jCoordinates (C_Dj, M_Dj, Y_Dj, K_i) Is obtained, a restriction coordinate search is performed. First, vertex D_jCoordinates (C_Dj, M_Dj, Y_Dj, K_i) As the target coordinates, and the calorimetric coordinates (X_Dj, Y_Dj, Z_Dj) As reference coordinates. At this time, the limit coordinates (C_Dj, M_Dj, Y_Dj, K_i) In the printer restriction profile (C)_Dj, M_Dj, Y_Dj, K) (K is a variable) is searched for a limit coordinate when the colorimetric coordinate associated with K is the closest to the reference coordinate.
[0096]
The combination of the target coordinates and the searched limited coordinates is sent from the coordinate search unit to the color conversion definition creation unit, as in the first embodiment.
[0097]
Thereafter, as in the first embodiment, the coordinate estimation unit calculates the limit coordinates of the printer color space that are associated with the coordinates of points other than the predetermined plurality of points in the print color space, and the color conversion definition creation unit calculates the print color. A color conversion profile in which the coordinates in the space and the restriction coordinates in the printer color space are associated is created.
[0098]
In this way, the total amount of ink can be limited while keeping the color as much as possible by searching for the limit coordinates while changing the K component without changing the C, M, and Y components.
[0099]
Here, the case where both the print color space and the printer color space are CMYK color spaces has been described above, but the target color space and the output device color space referred to in the present invention are not limited to the CMYK color spaces. For example, the color space may be an RGB color space or a color space in which colors are expressed by five or more color components, and the target color space and the output device color space may be different from each other. .
[0100]
In the above description, the proof image creation system has been described in which a printer that does not have an image development function for developing halftone data into bitmap format image data is applied. The limited image data in which the amount of ink is limited by the conversion device may be sent directly to the printer without passing through the image development device to generate a proof image.
[0101]
In the above description, the example in which the coordinates of the vertices in a series of target color spaces in which the K component is fixed is applied as the coordinates of a plurality of points in the target color space has been described. You may apply the coordinate of several points other than the vertex on a target color space.
[0102]
In the above, based on the correspondence between the target coordinates at a plurality of points in the target color space and the restricted coordinates on the printer color space, the correspondence between the target coordinates and the restricted coordinates at points other than the plurality of points on the target color space is shown. Calculated by interpolation calculation, based on the conversion coefficient for converting target coordinates at multiple points on the target color space to restricted coordinates on the printer color space, the target coordinates at points other than the multiple points on the target color space The correspondence with the limit coordinates may be calculated.
[0103]
In the color conversion definition creating apparatus or the color conversion definition creating program of the present invention, the “corresponding acquisition unit”, “coordinate search unit”, and “corresponding estimation unit” are provided in the same device or program. Alternatively, it may be provided in a separate device or program, and any specific implementation is possible as long as the color conversion definition creating method of the present invention can be realized.
[0104]
Furthermore, in the above description, a color conversion device that separately includes a color correction device that corrects the color of an image represented by image data and a color conversion device that converts image data in the print color space into restricted image data in the printer color space will be described. However, in the color conversion definition creating method of the present invention, one profile may be created in which the processes performed by these devices are collectively performed.
[0105]
【The invention's effect】
As described above, according to the present invention, the total amount of ink can be limited while maintaining the color reproduction region in the output device.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a printing and proof image creation system to which an embodiment of the present invention is applied.
2 is an external perspective view of a colorimeter and a personal computer shown in FIG. 1. FIG.
FIG. 3 is a hardware configuration diagram of a personal computer.
FIG. 4 is a schematic diagram of a color chart.
FIG. 5 is a conceptual diagram showing a CD-ROM in which an embodiment of a color conversion definition creating program of the present invention is stored.
FIG. 6 is a functional block diagram of a color conversion apparatus which is an embodiment of a color conversion definition creation apparatus of the present invention.
FIG. 7 is a flowchart showing a series of processing performed in RIP.
FIG. 8 is a flowchart showing an embodiment of a color conversion definition creation method of the present invention.
FIG. 9 is a conceptual diagram of a print profile.
FIG. 10 is a conceptual diagram of a printer restriction profile.
FIG. 11 is a diagram illustrating a series of color spaces in which a K component is fixed to each coordinate of the print color space in the print profile T.
FIG. 12 is a conceptual diagram of a color conversion profile.
[Explanation of symbols]
10 Color scanner
11 Document image
20 workstations
30 Film printer
40 printing press
41 Print image
50 Personal computer
51 Main unit
51a FD loading port
51b CD-ROM loading slot
52 Image display device
52a Display screen
53 keyboard
54 mouse
55 bus
60 Printer
61 Proof Image
70 Colorimeter
90 color chart
91a, 91b, ... color patch
100 RIP
110 Color correction device
120 color converter
121 Correspondence acquisition unit
122 Coordinate search unit
123 Correspondence estimation part
124 Color conversion definition creation part
125 Image data converter
130 Image development device
140 Page description data expansion device
200 color conversion profile
511 CPU
512 Main memory
513 Hard disk device
514 FD drive
515 CD-ROM drive
516 I / O interface
520 FD
521 CD-ROM
530 color conversion program
531 Correspondence acquisition unit
532 Coordinate search unit
533 Correspondence estimation part
534 Color conversion definition creation part
535 Image data converter
600 Cubic color space
T print profile
P Printer restriction profile

Claims (5)

An output device that outputs target coordinates on a target color space depending on a target device that outputs an image based on image data, and a proof image that reproduces the target image obtained when the image is obtained by the target device, based on the image data In a color conversion definition creation method for creating a color conversion definition that represents a correspondence with a limit coordinate that exists in a dependent output device color space and that is configured such that the sum of coordinate components constituting the coordinate is limited to a predetermined limit value or less.
A correspondence acquisition process for acquiring a correspondence relationship between the restriction coordinates and the color measurement coordinates on the device-independent color measurement color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, within the range of the limited coordinates associated with the colorimetric coordinates by the correspondence acquired in the correspondence acquisition process, A coordinate search process for searching for limited coordinates whose corresponding colorimetric coordinates are closer to the reference;
A color conversion definition creating method comprising: a color conversion definition creating step of creating a color conversion definition by associating the target coordinates with the limited coordinates searched in the coordinate search process. In the correspondence acquisition process, the color patch of the color chart output by the output device is measured based on the chart data defined by the restricted coordinates, which represents a color chart in which a plurality of color patches are arranged. The color conversion definition creating method according to claim 1, wherein the correspondence relationship between the restriction coordinates and the colorimetric coordinates obtained by the step is acquired. The coordinate search process is a process of applying a target coordinate of each of a plurality of predetermined points on the target color space as a target coordinate of the target, and searching for a limited coordinate for each target coordinate of each target,
The correspondence between the target coordinates of the points other than the predetermined plurality of points and the limit coordinates is estimated based on the correspondence between the target coordinates and the limit coordinates of the predetermined plurality of points obtained in the color conversion definition creation process. The color conversion definition creating method according to claim 1, further comprising a correspondence estimation process. An output device that outputs target coordinates on a target color space depending on a target device that outputs an image based on image data, and a proof image that reproduces the target image obtained when the image is obtained by the target device, based on the image data In a color conversion definition creating apparatus that creates a color conversion definition that represents a correspondence with a limit coordinate that is present on a dependent output device color space and that is a sum of coordinate components that constitute coordinates is limited to a predetermined limit value or less.
A correspondence acquisition unit that acquires a correspondence relationship between the restriction coordinates and the colorimetric coordinates on the device-independent colorimetric color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, within the range of the limited coordinates associated with the colorimetric coordinates by the correspondence acquired by the correspondence acquisition unit, A coordinate search unit for searching for a limited coordinate whose corresponding colorimetric coordinate is closer to the reference;
A color conversion definition creating apparatus comprising: a color conversion definition creating unit that creates a color conversion definition by associating the target coordinates with the limited coordinates searched by the coordinate search unit. A target coordinate on a target color space that is executed in a computer and depends on a target device that outputs an image based on image data, and a proof image that reproduces the target image when the image is obtained by the target device. Creates a color conversion definition that represents the correspondence with the limit coordinates that exist in the output device color space that depends on the output device that outputs based on the image data, and the sum of the coordinate components that make up the coordinates is limited to a predetermined limit value or less. In the color conversion definition creation program to
A correspondence acquisition unit that acquires a correspondence relationship between the restriction coordinates and the colorimetric coordinates on the device-independent colorimetric color space;
When the colorimetric coordinates associated with the target coordinates of the target with a predetermined correspondence are used as a reference, within the range of the limited coordinates associated with the colorimetric coordinates by the correspondence acquired by the correspondence acquisition unit, A coordinate search unit for searching for a limited coordinate whose corresponding colorimetric coordinate is closer to the reference;
A color conversion definition creation program, comprising: a color conversion definition creation unit that creates a color conversion definition by associating the target coordinates with the limited coordinates searched by the coordinate search unit.

Images