JP2013115588A - Color processing apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize color conversion making the most use of the color region reproduction of an output device, on even an input image which is to be printed by standard printing.SOLUTION: A color processing apparatus stores profiles in a profile storage area (100), and selects either a first output profile aiming at colorimetry matching with the standard output profile associated with input data or a second output profile which is expanded or compressed depending on the standard output profile and the color region of a digital printer (102). The color processing apparatus performs color conversion on the input data by the first output profile or the second output profile (106, 108 to 114, 122).

Description

  The present invention relates to a color processing apparatus and program, and more particularly, to a color processing apparatus that performs color processing such as color conversion in different device color spaces, and a color processing program that causes a computer to function as the color processing apparatus.

  Input / output devices such as a color printer, a display, and a scanner connected to a computer have different color reproduction characteristics such as a color gamut. For this reason, when transferring colors between devices, the color reproduction of each device is intended to reproduce the color as intended by the user on each device by correcting the differences in the color reproduction characteristics of each device. Color conversion is performed according to a profile prepared for each device according to characteristics (for example, a color conversion condition for performing color conversion between a device-dependent color space that depends on the device and a device-independent color space that does not depend on the device). .

  That is, color processing such as color conversion is required to match different device color spaces (color gamuts). The device color space is, for example, a color space using four or more inks (color materials) for devices represented by image output apparatuses such as printing and electrophotography, and an RGB color space for devices such as monitor displays and cameras. Has been. As a color space for achieving consistency, a color space having a feature of a color appearance model such as CIECAM02 or a perceptual uniform color space such as CIELAB is used. Further, tristimulus values CIEXYZ and LMS color space are also used.

  Many techniques for matching such different device color spaces (color gamuts) have been proposed. For example, a technique relating to color gamut mapping that handles color gamut expansion is disclosed (see Patent Document 1). Further, as a technique relating to color gamut mapping, a technique is disclosed in which most of the color gamut mapping is faithfully reproduced and only a part of the color gamut is compressed / expanded (see Patent Documents 2 to 4). Furthermore, a technique for performing color processing using a virtual color gamut including a plurality of printing devices is disclosed (see Patent Document 5).

JP 63-132592 A Japanese Patent Laid-Open No. 5-115000 JP-A-7-107306 Japanese Patent Laid-Open No. 10-178557 JP 2002-252785 A

  By the way, in a general printing process, CMYK is adopted as a color space for proofreading, plate making, and printing output. The color by CMYK is, for example, Japan Color standard color. For operation in the printing process, a document created with CMYK or a layout of RGB images taken with a digital camera (such as a PDF / X (ISO15930) document or a metafile associated with a layout document) ) Is set with an output profile expressing the color features. This profile is, for example, a color conversion condition for performing color conversion between a device-dependent color that depends on the device and a device-independent color that does not depend on the device. In general, a standard print profile (for example, a Japan Color profile for standard printing) representing the characteristics of standard CMYK is set.

  On the other hand, digital printers (such as electrophotographic printers and inkjet printers) use CMYK color materials different from those used in printers (offset printing, etc.), use multiple colors to expand the color reproduction range, and even color. A narrow color gamut is used due to restrictions on the total amount of material. In order to use these expanded (reduced) color reproduction, a profile dedicated to digital printers may be used. However, in many cases, the quality of the printed material cannot be confirmed during the printing process. A print workflow for printing (for example, newspaper, magazine, commercial printing, etc.) is adopted, and is limited to the standard CMYK output profile set in operation. Therefore, the output color of the set output profile is used as a target, color conversion is performed so that the same color is obtained with an actual digital printing machine, and output is performed with a digital printing machine. The wide color gamut provided by digital printers that use multiple colors to expand the gamut is not used. Further, in a digital printer with a narrow color gamut, the minimum brightness is higher than the minimum brightness in the standard CMYK color gamut, so using a corresponding color with the smallest color difference causes gradation breakdown and poor print quality.

  The color processing apparatus according to the first aspect of the invention uses a profile associated with input data representing an image to store a first output profile for colorimetric matching with an output device for the profile. A storage for storing a second output profile that is subjected to color gamut mapping that approximates the output of the profile using the color gamut of the output device while limiting the color gamut that matches the colorimetry with reference to the profile. Means, a selection means for selecting the first output profile or the second output profile, a profile associated with the input data, and a first output profile indicating characteristics of the color selected by the selection means Alternatively, the second output profile is used to color the input data color data into the output device color data. It includes a color conversion unit for conversion, the.

  The invention according to claim 2 is the invention according to claim 1, wherein the storage means adds one or more specific colors to the basic color corresponding to the output device with respect to the basic color of the profile associated with the input data. A second output profile indicating the color characteristics by color is stored.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the selection unit is configured such that the color gamut size difference between each of the first output profile and the second output profile, or A difference in minimum brightness is obtained, and if the obtained difference in color gamut size or difference in minimum brightness is greater than a predetermined value, the second output profile is selected.

  According to a fourth aspect of the present invention, in the color processing apparatus according to the third aspect, the selection unit is configured such that color data of maximum saturation on the outline of a color gamut according to the second profile corresponding to the output device is the profile. Judgment is made by out of the color gamut.

  According to a fifth aspect of the present invention, in the color processing apparatus according to any one of the first to fourth aspects, the color conversion unit includes a color gamut mapping unit, and the color gamut mapping unit includes the profile. In accordance with the color rule with reference to the above, the reproduction color is associated using expansion, maintenance, or compression.

  According to a sixth aspect of the present invention, in the color processing apparatus according to the fifth aspect, the color gamut mapping unit sets a color rule for maintaining device-independent data included in a predetermined designated color region.

  According to a seventh aspect of the present invention, in the color processing apparatus according to the sixth aspect, the predetermined designated color region is a skin color region of a person.

  According to an eighth aspect of the present invention, there is provided a color processing program that uses a profile associated with input data representing an image as a first output profile aiming at colorimetric matching with an output device for the profile. And storing a second output profile that is subjected to color gamut mapping that approximates the appearance of the output of the profile using the color gamut of the output device while limiting the color gamut that matches the colorimetry with reference to the profile. A selecting means for selecting the first output profile or the second output profile from a storing means for storing, a profile associated with the input data, and a first characteristic indicating the characteristics of the color selected by the selecting means. The output data or the second output profile is used to convert the input color data into the previous A color converting means for color conversion to the color data of the output device, to function as a.

  According to a ninth aspect of the present invention, a color processing program causes a computer to function as each means constituting the color processing device according to any one of the first to eighth aspects.

  According to the first, eighth, and ninth aspects of the present invention, the color gamut of the output device is effectively used so that the color reproduction by the profile aiming at the colorimetric match and the output of the output device by the profile associated with the input data are closer to the appearance. It has an excellent effect that it can be selected from color reproduction based on the profile obtained.

  The invention according to claim 2 can be selected from color reproduction based on a profile indicating a color characteristic of a basic color associated with input data and color reproduction based on a profile indicating a color characteristic of a specific color corresponding to the output device. Has an effect.

  The invention described in claim 3 has the effect that the color reproduction can be selected by judging the size of the color gamut or the difference in the minimum brightness.

  The invention described in claim 4 has the effect that color reproduction can be selected by judging the size of the color gamut based on the maximum saturation.

  The invention described in claim 5 has the effect that color conversion can be performed by associating reproduced colors in accordance with the color rule.

  The invention described in claim 6 has the effect that the color data can be maintained for the color of the predetermined designated color region.

  The invention according to claim 7 has an effect that the skin color of a person can be appropriately reproduced.

1 is a block diagram showing a schematic configuration of a computer system according to a first embodiment. It is a functional block diagram of the color conversion process which concerns on 1st Embodiment. It is explanatory drawing of the profile selection part of the color conversion process part which concerns on 1st Embodiment. It is a flowchart which shows the content of the color gamut mapping process which concerns on 1st Embodiment. It is the schematic which shows an example of the color gamut outline of the digital printing machine in the standard color space depending on a digital printing machine. It is the schematic which shows an example of the color gamut outline of the digital printing machine in the extended color space depending on a digital printing machine. FIG. 3 is a schematic diagram illustrating an example of a color gamut outline (output color gamut) of a digital printing machine in a device-independent color space. It is a functional block diagram of the color conversion process which concerns on 2nd Embodiment. It is a flowchart which shows the content of the color gamut mapping process which concerns on 2nd Embodiment. It is a functional block diagram of the color conversion process which concerns on 3rd Embodiment. It is a flowchart which shows the content of the color gamut mapping process which concerns on 4th Embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of a computer system 10 according to the present embodiment. The computer system 10 includes a plurality of client terminals 26 including PCs (Personal Computers) and the like on a network 12 including a LAN, an output device 18 that visualizes input image data as a reflector, A processing server 14 (for example, RIP: Raster Image Processor) that converts to an output device color using a color conversion condition for outputting to an output device is connected to each other. Examples of the output device 18 include a digital printing machine that prints an image represented by input image data on a sheet. An input device 16 for inputting image data can be connected to the network 12. The network 12 may also be connected to a computer network such as the Internet.

  In the present embodiment, as the output device 18, a digital printing machine that uses six color materials of CMYKAB in which specific color A and B color materials are added to each color material having CMYK as a basic color is used. explain. This does not need to be the specific colors A and B, and is a color gamut wider than the standard CMYK color gamut, or a narrow color gamut (for example, the minimum brightness is the standard CMYK The same configuration is applied to an output device that is brighter than the minimum lightness of the color gamut and has a gradation difference when the color difference is minimum.

  The processing server 14 connected to the network 12 includes a CPU 14A, a memory 14B including a RAM, a non-volatile storage unit 14C including an HDD (Hard Disk Drive) and a flash memory, and a network interface (I / F) unit 14D. And connected to the network 12 via the network I / F unit 14D. The processing server 14 is connected with a display 20 as a display device, a keyboard 22 and a mouse 24 as input means.

  The processing server 14 includes a server OS (Operating System) program, various application programs that operate on the server OS and use the output device 18, and a CMM (color conversion module for performing color conversion processing on the processing server. ) Are installed in advance, and initial profiles (input profiles and output profiles set at the time of product shipment) used in color conversion processing, programs for generating profiles under arbitrary conditions, and base data (measurement data, etc.) are also available Each is memorized. The profile indicates a color conversion condition when performing color conversion between arbitrary color system data and device-independent color space data. An example is the ICC profile (ISO 15076-1).

  The storage unit 14C of the processing server is provided with a profile storage area 15 for storing profiles. This profile storage area 15 is for storing an output profile or the like used in color conversion processing to be described in detail later. The profile storage area 15 contains an output profile (an output associated with input data). Profile), an output device profile that is a profile according to the characteristics of the output device, or a standard print profile determined in advance as a standard.

  In this embodiment, input files (including input profiles and output profiles) represented by image data and PDF documents are used as data. The input profile (input device profile corresponding to the characteristics of the input device) is a color conversion condition for converting device-dependent data (input device-dependent color) into device-independent data (device-independent color). The output profile (specific device profile according to the characteristics of a specific device) is a color conversion condition for converting device-independent data into device-dependent data (predetermined specific device dependent color). The predetermined device-dependent color is a device-dependent color assuming that input data is output from the device. In the printing process, multiple creators (designers, layouters, etc.) and order managers (clients) need to confirm the reflections and proceed with the work, and a print workflow (for example, PDF workflow) is in place. Yes.

  For this reason, a profile is set in an input file premised on printing / printing. In this profile, if the input file is configured in CMYK colors, the device-dependent data of the input profile is CMYK. If the input file includes RGB colors, the device-dependent data of the input profile is RGB and the device-dependent data of the output profile is, for example, CMYK. Each profile here is, for example, a file laid out as a PDF / X file, a RGB image shot with DSC (taken with a digital camera), and a file with an output profile set as a metafile associated with it. Applicable. As described above, there are cases where only the input profile is used or cases where the input profile and the output profile are used. Here, a case where the input profile and the output profile are specified in the input file will be described.

  One of the output profiles here is the standard print profile. The standard print profile has different standard settings in each country even if ISO-compliant printing process management is performed. For example, Japan Color (paper CMYK colors are different for each market), JPMA colors (CMYK colors of the Japan Magazine Association), digital printer companies or colors managed by printing companies that use them are used. If not set, the initial profile setting of each processing server is used. All of these standard print profiles output the CMYK color space. In this embodiment, a standard print profile will be described as an output profile. In the output color generation of the output device using the standard print profile (target output profile), the output profile (standard print profile) for "Generate same color with colorimetric match" for the standard print profile color For generating “near-looking colors (in other words, colors with a similar impression or consistent colors)” with reference to the standard printing profile An output viewpoint selection unit capable of selecting an option to generate and use an output profile (hereinafter referred to as an extended print profile) is provided. The former can use a well-known Colorimetric algorithm, minimum color difference, and the like, and further has options such as K storage and specific color (for example, one of CMY pure colors) storage as options. Hereinafter, the latter generation means will be mainly described.

  Each client terminal 26 includes a CPU (not shown), a memory such as a RAM, a nonvolatile storage unit such as an HDD (Hard Disk Drive) or a flash memory, and a network interface (I / F) unit. It is connected to the network 12 via a network I / F unit. The client terminal 26 is connected to a display device, a keyboard, and a mouse, which are display devices.

Next, the operation of this embodiment will be described.
The processing server 14 according to the present embodiment is configured to function as a color conversion processing unit and a profile generation unit illustrated in FIG. The color conversion processing unit includes a CMM unit that performs color conversion processing by the CMM and a profile selection unit. The CMM unit performs color conversion processing when image data input from one input device 16 or image data used for printing an image on one output device 18 is used for printing an image on another output device 18. Is to do. Select the profile selection unit when using the standard print profile as it is, or when using a color gamut effectively on a digital printing press and using a reproduction that looks similar to the standard print profile output (extended print profile). It is configured to be able to. Effective use here is not pasting the former as it is (color gamut clipping processing or color difference minimization processing), but changing it according to the output color gamut. On the other hand, processing is performed in consideration of color reproduction and gradation based on a predetermined viewpoint (reproduction that looks close to the standard print profile output). In addition, the processing server 14 is configured to function as a profile generation unit, and an example of the profile generation unit corrects a difference in color reproduction characteristics for each device and corrects a color as intended by the user in each device. Is realized by a configuration including a color gamut mapping process for reproducing the color and a color separation process for reproducing the color reproduction characteristics of each device.

  Hereinafter, the input file input to the processing server 14 is assumed to be image data for the sake of explanation. This is image data representing the color of each pixel of the input image data as color data on a color space (eg, RGB color space) depending on the first device. The output profile is determined in accordance with a selection made by the profile selection unit or a setting previously selected on the user interface (a reference file corresponding to the input file such as a metafile). In the color conversion process (CMM process) on the processing server 14, the first device is based on the input profile included in the input file, the determined output profile (output target), and the user's instruction or a preset viewpoint. Convert dependent color to output device dependent color. When the input profile and the output profile are not specified in the input file, the input side and output side initial profiles stored in the storage unit 14C are used.

  Next, an example of an extended print profile generation method will be described. Profile generation mainly includes color gamut mapping processing and color separation processing. For the color separation processing, a known method or an output profile (Colorimetric Intent) attached to an output device can be used.

  The color gamut mapping process uses the color rules to change the color appearance difference of each device (this difference in appearance is mainly due to the difference in the color gamut (color reproduction gamut) of each device). This is a process of correcting so as to be within the color gamut of the output device while being corrected by (the individual rules constituting the gamut mapping algorithm).

  As this color rule, a color rule known in color gamut mapping can be used. Examples of color rules include color preservation rules based on judgments, rules for saturation mapping with equal hues, hue rotation with emphasis on saturation, rules for obtaining the smallest evaluation function (color difference, etc.), and aiming for each output device. In addition, for input data that is located in the input color gamut that overlaps the output color gamut, the input data is used as output data as it is (input Data and output data are colorimetrically matched), and input data that is located in the input color gamut that does not overlap with the output color gamut is mapped and output so that it falls within the output color gamut. Use paste-type color rules for obtaining data, and compression / decompression-type color rules for mapping output data to obtain output data in order to preserve the relative relationship between points in the input color gamut. It is possible. Also, in the pasted color rule, a method that maps colors outside the output gamut to the outline of the output gamut without changing the hue and brightness so that the brightness is preserved, Therefore, there is a method of mapping a color outside the output color gamut to the outline of the output color gamut without changing the hue, and any of them may be used. Also, there is a method of mapping so that gradation is preserved for the compression / expansion type color rule, and this may be applied. Further, an adaptive color rule that maps differently for each region may be used. For example, a color rule that combines a pasting type and a compression / expansion type may be used.

  Next, profile selection processing by the profile selection unit in FIG. 2 will be described with reference to FIG. The selection process by the profile selection unit in FIG. 2 performs color reproduction close to the appearance with reference to the first output profile as a color reproduction matching color reproduction viewpoint and the same output profile for the output profile composed of CMYK colors. This is a process of selecting one of the output profiles of the second output profile based on the extended color obtained by adding the specific colors A and B (see also FIG. 3). When no output profile is specified in the input file, the output-side initial profile (targeting CMYK colors) stored in the storage unit 14C is used.

  In addition, a control value indicating an instruction to select one of the first output profile and the second output profile is input to the profile selection unit. A control value indicating an instruction for selecting the output profile can be input by selecting either the keyboard 22 or the mouse 24.

  The profile storage area 15 in the storage unit 14C of the processing server stores a first output profile based on output profile information (for example, standard print profile or character information for specifying a profile) included in the input file. In addition, a second output profile (extended print profile) referring to the output profile of the output device 18 is stored.

  The output profile generates a color agreed with the client in operation, and the color of the output profile and the color of the first output profile are generally colorimetrically matched. In other words, this is an output profile for color conversion by linking one of the following two output profiles to an output profile (for example, a standard print profile) targeting CMYK colors. One is an output for generating CMYK (CMYK colors in an extended color space of 6 colors) color data of an output device (in this embodiment, a digital printer capable of outputting in a 6 color space) from CMYK color data of the input device. It is a profile. The other is an output profile using all six colors. The former can suppress the amount of color material used, and the latter can increase the color reproduction accuracy (color difference and gradation reproducibility). The first output profile may be stored in advance, or may be generated and stored.

  The second profile is an output profile that effectively uses the output device color gamut. In other words, with reference to an output profile (standard print profile) for CMYK colors, expansion is performed by adding specific colors A and B to CMYK colors of the output device from CMYK color data (target color) corresponding to the input device. This is an output profile that combines the expansion of only a necessary region and the matching of color tone reproduction (appearance closeness) to generate color data. The second output profile may be stored in advance, or may be generated and stored.

  Next, referring to FIG. 4, it is possible to select to perform the intended color reproduction in the input file and to effectively reproduce the color gamut of the output device while considering the intended color reproduction in the input file. The intended color conversion process will be described. Here, description will be made including generation of an output profile corresponding to the output device.

  In the color conversion process, first, in step 100, the profile is confirmed, and this profile is stored in the profile storage area 15. Specifically, the output profiles included in or associated with the input file are confirmed and stored in the profile storage area 15. When these profiles are not included in the input file, the initial profile (standard print profile) is stored in the profile storage area 15.

  In the present embodiment, for example, the output device is a digital printing machine, the output device dependent colors assumed in the input file are C, M, Y, and K, and the output device dependent colors actually produced by the digital printing machine to be output are The case of C, M, Y, K, A, B will be described. In this embodiment, a case will be described in which a profile is not included in an input file and a standard print profile is set as an initial profile.

  Note that colors (specific colors) other than the CMYK basic colors adopted as the extended colors are not limited to two, A and B. The specific color may be one or three or more as long as the color gamut is expanded.

  In the next step 102, the input control value is determined, and it is determined whether the selection instruction is the first output profile or the second output profile. That is, it is determined whether or not the extended print profile that is the second output file is selected. If the result in Step 102 is negative and the instruction is to perform color conversion based on the output profile included in the input file (the output profile associated with the input data), the process proceeds to Step 104. On the other hand, if the determination in step 102 is affirmative and the instruction is to perform color conversion using an output profile (extended print profile) according to the characteristics of the output device, the process proceeds to step 106.

  In step 104, points constituting the color gamut outline of the digital printer in the color space assumed in the input file among the color spaces depending on the digital printer as the output device constituting the polygon (polyhedron) (outline plane) Set the upper point as the outline point group. Here, FIG. 5 shows an example of the color gamut outline of the digital printing machine when it is assumed that the digital printing machine forms an image with a total of four color materials of C, M, Y, and K. 5A shows the upper part of the color gamut outline in the CMYK color space, FIG. 5B shows the lower part, and the entire color gamut outline of the digital printing machine in the CMYK color space is shown in FIG. It becomes a 12-sided polyhedron combining the solids shown in 5 (A) and (B).

  In step 106, the points (points on the outer surface) constituting the color gamut outline of the digital printing machine on the color space depending on the digital printing machine as the output device constituting the polygon are set as the outline point group. Here, the digital printing machine is configured to form an image using a total of six color materials of C, M, Y, K, A, and B. FIG. 6 shows, as an example, a digital printing machine in an extended color space (CMYKRG color space) depending on the digital printing machine when two colors A and B are associated with R (red) and G (green). The color gamut outline was shown. 6A shows the upper part of the color gamut outline in the extended color space by CMYKRG, and FIG. 6B shows the lower part of the color gamut outline of the digital printing machine in the extended color space by CMYKRG. The whole is a polyhedron combining the solids shown in FIGS. 6 (A) and 6 (B).

  In the next step 108, the color data of the digital printer in the device-independent color space (output) is converted by converting the color data of the outline points set in step 104 or 106 into the color data of the device-independent color. Each outline point group representing the outline for each color gamut) is obtained. The conversion of step 108 can be realized by using, for example, an output device profile (for example, B2A profile of Colorimetric Intent). As an example, FIG. 7 shows an example of a color gamut outline composed of outline points obtained by applying the CIELAB color space as the device-independent color space and converting the CMYK color space through Step 108. In FIG. 7, the vertices of the color gamut outline are denoted by the same reference numerals as the corresponding vertices among the vertices of the color gamut outline shown in FIG. 5. Through the above process, the color gamut outline information of the digital printing machine can be obtained. The same applies to the extended color space.

  Next, in step 110, a standard print profile is acquired, and an output profile corresponding to the color gamut of the digital printing machine is generated with reference to the standard print profile. Although the ICC B2A profile format is possible, the device link format will be described here. Specifically, a standard print profile (for example, A2B profile of Colorimetric Intent) is obtained from a color look-up table (CLUT), which is a large number of grid point data that are equally positioned in the same CMYK space as the output of the standard print profile. The data is generated as a CIELAB data group. Next, in step 112, the color rule in the color gamut mapping similar to the standard printing profile (for example, B2A profile of Perceptual Intent) is applied to the CLUT, and the position in the device-independent color space is output. By performing conversion so as to be within the gamut outline, a CLUT after gamut mapping is generated. This output color gamut outline can be set from the obtained output color gamut outline information by obtaining output color gamut outline information indicating the color gamut outline at the outline point group based on the color data converted in step 108. As an example of the color rule here, it is preferable to obtain a large tendency with a statistical model. For example, the discrete correspondence between two CIELABs before and after color gamut mapping as a result of the color rule of a standard print profile (for example, B2A profile of Perceptual Intent) and the output color gamut of the standard print profile as multivariate learning data Using a statistical model such as analysis or multiple regression model, the corresponding CIELAB after mapping can be calculated using the color gamut of the digital printing press and CIELAB before mapping as input values. If it is necessary to control the color gamut mapping with higher accuracy, the color rule of the standard printing profile (for example, the B2A profile of Perceptual Intent) may be estimated and the same color rule may be used.

  When the CLUT after color gamut mapping is generated as described above, in the next step 114, each color is color-separated into CMYKAB colors, and an output profile is generated. That is, when the first output profile is instructed to be selected, an output profile that is colorimetrically matched with the standard print profile, for example, an output profile that uses the minimum color difference in K storage as a color rule is generated. On the other hand, when the second output profile is instructed to be selected, an extended print profile is generated as an output profile.

  Next, an output profile for performing color processing is selected according to the input control value, and color conversion is performed (step 122). That is, when the first output profile is selected and instructed, color reproduction can be performed almost faithfully to the standard print profile assumed in the input file. In addition, when the second output profile is selected and instructed, the appearance of the image on the first device and the image on the second device are caused mainly by the difference in color gamut between the first device and the second device with respect to the input data. The difference in appearance is corrected. In addition, color reproduction can be performed by effectively using a color gamut in a digital printing machine.

  As described above, in this embodiment, the input data is output so as to reproduce the color almost faithfully to the standard print profile assumed in the input file, and the difference in the appearance of the image caused mainly by the difference in the color gamut is suppressed. However, it is possible to select output so as to reproduce colors close to the output of the standard print profile by effectively using the color gamut in the digital printing machine. For this reason, the tendency of color reproduction can be selected according to the image formed with a digital printing machine.

  As the color gamut mapping method, for example, color data is converted so that the common area in the color gamut is colorimetrically matched and the outside of the common area is within the color reproduction gamut of the output device. Paste-type color gamut mapping (more specifically, this pasting-type color gamut mapping includes methods that prioritize the preservation of brightness and methods that prioritize the preservation of chroma), and the relative color data in the color gamut. Compression / expansion gamut mapping that maps color data to all areas in the gamut so that the relationship is preserved, adaptive gamut mapping that applies different mapping methods to each area in the gamut, and paste type Any of these mapping methods combining color gamut mapping and compression / expansion color gamut mapping (for example, partial colorimetric matching, partial compression, etc.) may be applied.

(Second Embodiment)
Next, a second embodiment will be described. This embodiment is applied to the case where an output profile used for color conversion is automatically selected. Since the present embodiment has substantially the same configuration as the above-described embodiment, the same portions are denoted by the same reference numerals and detailed description thereof is omitted. In the present embodiment, it is not necessary to input the control value shown in FIG.

Next, the operation of this embodiment will be described.
The processing server 14 according to the present embodiment is provided with a color conversion processing unit shown in FIG. The color conversion processing unit shown in FIG. 8 includes a profile selection unit including a determination unit for a color gamut difference (size difference).

  A selection process by the profile selection unit shown in FIG. 8 will be described. This selection process is a process of automatically selecting according to the color gamut difference of the output device with respect to the color gamut of the output profile (target, for example, standard print profile). As an example, an output profile of a first output profile limited to the color gamut of the basic colors of CMYK and a second output profile of an extended color obtained by adding specific colors A and B to the basic colors of CMYK. This is a process of automatically selecting according to the size of the color gamut. One of the color gamut differences is a process of automatically selecting light according to the difference in minimum brightness. The larger the color gamut difference, the more effective the second output profile. Here, a case where the color gamut is larger than the target color gamut will be described. A predetermined value is determined in advance in order to determine whether the color gamut difference is large.

  Therefore, the selection unit includes a color gamut difference determination unit. The color gamut size determination unit includes a second color composed of an extended color obtained by adding specific colors A and B to a basic color of CMYK with respect to a target color gamut of the first output profile composed of the basic color of CMYK. It is determined whether or not the target color gamut is large in the output profile. For example, the size determination is performed by determining whether or not the position of the maximum saturation is outside the color gamut of the CMYK color space for the maximum saturation of the color gamut outer shell of the digital printing machine that is the output device. Can be realized. When the color gamut of the CMYKAB color space targeted by the second output profile is larger than the color gamut of the CMYK color space targeted by the first output profile, the second output profile is automatically selected.

  Next, color conversion processing in the present embodiment will be described with reference to FIG.

  In the color conversion process according to the present embodiment, the profile is confirmed and stored in the profile storage area 15 in the same manner as described above (step 100). In the next step 130, the sizes of the color gamut based on the output profile (output profile associated with the input data) included in the input file and the color gamut based on the output device profile which is a profile according to the characteristics of the output device are determined. Ask. In the next step 132, it is determined whether or not the color gamut of the CMYKAB color space with extended colors is larger than the color gamut of the CMYK color space. This determination can be made based on the position of the maximum saturation of the color gamut outer shell or the absolute value as described above. Although it is desirable to arbitrarily set as a determination criterion for the magnitude of the difference, for example, any value of color difference (saturation difference) 3.0 to 10.0 may be used as the determination criterion.

  If the determination in step 132 is affirmative, in steps 134 to 138 and step 142, the extended color gamut mapping process is performed, then the color conversion process is performed, and this processing routine is terminated. That is, the second output profile is instructed to be selected, and color conversion is performed using an output profile (extended print profile) corresponding to the characteristics of the output device. On the other hand, if the result in Step 132 is negative, the selection process is terminated. In other words, the first output profile is selected and instructed, and color conversion is performed using the output profile (output profile associated with the input data) included in the input file (step 144). Note that the processing in step 142 and step 144 corresponds to the processing in step 122 in FIG.

  Steps 134 to 138 correspond to an example of the processing of steps 106 to 114 in FIG. That is, in the present embodiment, color reproduction corresponding to the output profile is realized by suppressing the difference in the appearance of the image, and color conversion that effectively uses the color gamut of the digital printing machine that is the output device is executed. First, in step 134, color data of a device-independent color (for example, CIELAB) is generated from CMYK colors, and a color gamut using this as input data group is acquired. Next, in step 136, the color gamut is expanded to the output device color gamut. In step 138, an output profile is generated through color gamut mapping.

  As described above, in this embodiment, the profile is automatically selected according to the size of the color gamut, so that color conversion is executed so that the color reproduction is performed almost faithfully to the standard print profile assumed in the input file, or the image is The color reproduction corresponding to the output profile can be realized by suppressing the difference in the appearance of the image, and the color conversion using the color gamut of the digital printer as the output device can be executed.

(Third embodiment)
Next, a third embodiment will be described. This embodiment is a modification of the second embodiment. Since the present embodiment has substantially the same configuration as the above-described embodiment, the same portions are denoted by the same reference numerals and detailed description thereof is omitted. Also in this embodiment, it is not necessary to input the control values shown in FIG.

Next, the operation of this embodiment will be described.
As shown in FIG. 10, in this embodiment, the color gamut difference determination unit instructs the profile generation unit to generate an output profile. Specifically, the color gamut difference determining unit instructs selection so that either the first output profile or the second output profile is output as the output profile. That is, when the size determination unit determines that the color gamut of the CMYKAB target in the second output profile is larger than the color gamut of the target CMYK color in the first output profile, the profile generation unit Is instructed to generate a second output profile, the generated output profile is stored as a second output profile, and this second output profile is selectively output as an output profile. On the other hand, in the case of reverse determination, the first output profile is selectively output.

  As described above, in this embodiment, when the profile is automatically selected according to the size of the color gamut, the second output profile is used as the target for the CMYK color gamut targeted by the first output profile. Since the second output profile is generated and selected when the color gamut of the CMYKAB color to be performed is large, the calculation load can be suppressed as compared to always generating the second output profile.

(Fourth embodiment)
Next, a fourth embodiment will be described. In the present embodiment, when color reproduction is performed almost faithfully to the standard print profile assumed in the input file, the influence of color conversion is suppressed for a predetermined color and the appearance of the color is maintained. Since the present embodiment has substantially the same configuration as the above-described embodiment, the same portions are denoted by the same reference numerals and detailed description thereof is omitted.

Next, the operation of this embodiment will be described.
As shown in FIG. 11, the color gamut mapping process of the present embodiment is obtained by replacing the process of step 112 in FIG. 4 with the processes of steps 150 to 154.

  As described above, a CIELAB data group is generated from a large number of grid point data groups that are equally positioned in the device-dependent color space as CLUT start data (step 110 in FIG. 4).

  In step 150, information relating to a predetermined specific color area is acquired. An example of the information regarding the specific color area is information indicating a color gamut indicating a human skin area. Note that the information regarding the specific color region is not limited to information indicating the color gamut indicating the skin region of the person. For example, a color region having a certain color data range such as information on a color region corresponding to a forest color or information on a color region corresponding to a sky such as a blue sky may be employed.

  In the next step 152, data included in the specific color area is classified as maintenance data based on the information regarding the specific color area acquired in step 150. Specifically, based on the information about the specific color area, using the input profile, the color gamut outline (outside the specific color gamut) corresponding to the specific color area of the first device (see FIG. 2) on the device-independent color space. Specific color gamut outline information representing the image), and based on the obtained specific color gamut outline information, data for many points located at different positions within the specific color gamut in the device-independent color space are input for maintenance. Generate and classify as a data group. In the next step 154, a color rule for maintaining the color data of the maintenance input data group generated in step 152 is added, and the color rule is applied to the input data group other than the maintenance input data group to make the device independent. The output CLUT after color gamut mapping is obtained by converting the position in the color space so that it is within the output color gamut outline represented by the output color gamut outline information.

  As a result, the input value of the color data corresponding to the specific color region is maintained in the color gamut mapping. Therefore, for example, for a color gamut indicating a human skin area, the color at the time of input can be reproduced.

  As described above, in the present embodiment, it is possible to maintain the color appearance by suppressing the influence of color conversion on a predetermined color. For this reason, it is possible to improve color reproduction for an image formed by a digital printing machine.

  In the above description, the digital printer has been described as an example of the output device. However, the present invention is not limited to this, and any device such as an image display device can be applied. In the above description, the CMYKAB color is applied as the output device-dependent color. However, these color spaces can be changed as appropriate according to the type of the device.

  In the above description, the color conversion program corresponding to the color processing program is stored (installed) in advance in the storage unit 14C of the processing server. However, the color processing program is recorded on a CD-ROM, DVD-ROM, or the like. It is also possible to provide it in a form recorded on a medium.

DESCRIPTION OF SYMBOLS 10 Computer system 14 Processing server 14B Memory 14C Storage part 16 Input device 18 Output device 26 Client terminal

Claims (9)

Using a profile associated with input data representing an image, a first output profile aiming at colorimetric matching with an output device is stored in the profile, and color areas that are colorimetrically matched with reference to the profile Storage means for storing a second output profile subjected to color gamut mapping that looks close to the output of the profile using the color gamut of the output device while restricting
Selecting means for selecting the first output profile or the second output profile;
Using the profile associated with the input data and the first output profile or the second output profile indicating the characteristics of the color selected by the selection means, the color data as the input data is converted to the output device. Color conversion means for color conversion to color data;
Including color processing device.   The storage means stores a second output profile indicating a color characteristic of a color obtained by adding one or more specific colors to the basic color corresponding to an output device with respect to a basic color of a profile associated with input data. Item 2. A color processing apparatus according to Item 1.   The selection unit obtains a difference in color gamut size or a difference in minimum brightness by each of the first output profile and the second output profile, and determines a difference in size of the obtained color gamut or minimum brightness. The color processing apparatus according to claim 1, wherein the second output profile is selected if the magnitude of the difference is greater than a predetermined value.   The color processing apparatus according to claim 3, wherein the selection unit determines that the color data of the maximum saturation on the outline of the color gamut according to the second profile corresponding to the output device is out of the color gamut of the profile.   The color conversion unit includes a color gamut mapping unit, and the color gamut mapping unit associates reproduced colors by using expansion, maintenance, or compression according to a color rule with reference to the profile. Item 5. The color processing apparatus according to any one of Items 4 to 4.   The color processing apparatus according to claim 5, wherein the color gamut mapping means sets a color rule for maintaining device-independent data included in a predetermined designated color area.   The color processing apparatus according to claim 6, wherein the predetermined designated color region is a human skin color region. Computer
Using a profile associated with input data representing an image, the profile is stored as a first output profile aiming at colorimetric matching with an output device, and a color region that is colorimetrically matched with reference to the profile From the storage means for storing the second output profile that has been subjected to color gamut mapping that looks close to the output of the profile using the color gamut of the output device while limiting the output, the first output profile or the second output profile is stored. A selection means for selecting an output profile of
Using the profile associated with the input data and the first output profile or the second output profile indicating the characteristics of the color selected by the selection means, the color data as the input data is converted to the output device. Color conversion means for color conversion to color data;
Color processing program to function as   The color processing program for functioning a computer as each means which comprises the color processing apparatus of any one of Claims 1-8.

Images