JP2006345358A - Apparatus, method and program for generating color collection profile, and print control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily generate a color correction profile with high accuracy. <P>SOLUTION: By performing color conversion onto an image data of a color chart by referring to a color conversion profile generated according to target colors G<SB>1</SB>, G<SB>2</SB>, color patches can be generated with substantially identical colors to the target colors G<SB>1</SB>, G<SB>2</SB>in a printed color chart. Accordingly, even without preparing different color charts for each of target colors G<SB>1</SB>, G<SB>2</SB>, a color correction profile having high accurately is generated using the color chart for general use. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color correction profile creation apparatus, a color correction profile creation method, a color correction profile creation program, and a print control apparatus.

  Conventionally, in this type of color correction profile creation apparatus, a plurality of color correction profiles have been created so that a user can specify a target color to be printed on a printing paper. For example, when an achromatic color is printed, a color correction profile in absolute gray mode that reproduces a true achromatic color by colorimetry, and twisting on printing paper that is not a true achromatic color by colorimetry It is known to prepare a paper-mode color correction profile that can express a natural gray gradation. According to this configuration, it is possible to obtain a printing result that satisfies the user even for a monochrome image that requires color accuracy.

In order to create a color correction profile that can accurately reproduce the target color, a color chart that contains many color patches of colors that approximate the target color is actually printed, and the color measurement results are reflected in the color correction profile. It is desirable. However, according to a general-purpose color chart, it is not always possible to create a color correction profile that can accurately reproduce a target color because a large number of color patches that approximate the target color are not printed. there were. Although it is conceivable to prepare a color chart on which many color patches of colors close to the target color are printed, there is a problem that the color chart must be prepared individually and is complicated.
The present invention has been made in view of the above-described problems, and provides a color correction profile creation device, a color correction profile creation method, a color correction profile creation program, and a print control device capable of easily creating a precise color correction profile. The purpose is to do.

Means and effects for solving the problem

  In order to solve the above-mentioned problem, in the invention according to claim 1, the target color acquisition means acquires the target color to be reproduced on the printing paper in the first color space. The color conversion profile creation means creates a color conversion profile that defines the correspondence between the second color space and the third color space. In this color conversion profile, when a color chart is printed on the printing paper while performing color conversion with reference to the same color conversion profile, a color patch having substantially the same color as the target color acquired in advance is reproduced. As described above, the correspondence relationship between the second color space and the third color space is corrected. Therefore, a color patch having substantially the same color as the target color is reproduced on the color chart printed by the color chart printing means. The color correction profile creating means associates the color correction profile by associating the specific color with a color coordinate in the second color space where the target color can be reproduced based on the color measurement result of the color chart. create.

  The color chart that is printed while performing color conversion with reference to the color conversion profile is formed with the color patch that is substantially the same color as the target color, and thus obtains a color measurement result for the target color. be able to. Accordingly, the accuracy of estimating the color coordinate in the second color space where the target color can be reproduced based on the color measurement result of the color chart is improved, and the correspondence between the color coordinate and the specific color is accurately performed. be able to. Therefore, the color correction profile capable of accurately reproducing the target color can be created. Even for the general color chart, color patches having substantially the same color as the target color can be printed by performing color conversion with reference to the color conversion profile. Therefore, it is not necessary to prepare the color chart individually for printing a color patch having substantially the same color as the target color.

  In the invention according to claim 2, in the correspondence relationship between the second color space and the third color space in the color conversion profile, the variable region in which the correspondence relationship is corrected according to the target color. And an invariant region in which the correspondence is constant regardless of the target color. Accordingly, even when a plurality of target colors are set for the specific color, it is possible to correct only the variable region without correcting the entire color conversion profile. That is, it is not necessary to prepare a plurality of the entire color conversion profiles for each target color. For example, by preparing an invariant table that defines the invariant region and a plurality of variable tables for each target color that defines the variable region, and replacing only the variable table according to the target color, the variable region Can be corrected according to the target color.

Furthermore, in the invention according to claim 3, the specific color is an achromatic color of each brightness in the first color space, and the target color corresponding to the achromatic color is set. In this case, the target color is a color having a linear color change between the brightest color and the darkest color that can be expressed on the printing paper. The brightest color that can be expressed on the white printing paper is the color of the paper of the printing paper. Since the achromatic color of each lightness changes linearly, the gradation of the achromatic color can be reproduced without color twist.
In the invention according to claim 4, the specific color is an achromatic color of each brightness in the first color space, and the target color corresponding to the achromatic color is set. In this case, the target color is an achromatic color of each brightness on the printing paper. That is, when the achromatic color of each lightness in the first color space is reproduced on the printing paper, the achromatic color of each lightness can be reproduced on the same printing paper. That is, the achromatic color of each lightness in the first color space can be accurately reproduced on the printing paper as it is.

  Of course, the above invention can be realized not only by the apparatus but also by the color correction profile creation method as in claim 5, and color correction for executing processing according to the method as in claim 6. It can also be realized by a profile creation program. Furthermore, it is also possible to realize as a print control apparatus that performs printing based on the color correction profile created by the color correction profile creation apparatus as in the seventh aspect. Further, it can be realized as a print control method and a print control program corresponding to this print control apparatus. In addition, the idea of the invention is that the apparatus, method, and program according to the present invention may be implemented independently, or may be implemented together with other apparatuses, methods, and programs while being incorporated in a certain device. Is not limited to this, and includes various aspects, and can be changed as appropriate.

  Further, it can be provided as a recording medium on which the program of the present invention is recorded. The recording medium for this program may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium that will be developed in the future. In addition, the duplication stages such as the primary duplication product and the secondary duplication product are equivalent without any question. Further, even when a part is software and a part is realized by hardware, the idea of the invention is not completely different, and a part is stored on a recording medium and is appropriately changed as necessary. It may be in the form of being read. Further, not all functions are necessarily realized by a single program, but may be realized by a plurality of programs. In this case, what is necessary is just to make each function implement | achieve in a some computer.

Here, embodiments of the present invention will be described in the following order.
(1) Configuration of color correction profile creation device:
(2) Color correction profile creation processing:
(3) Print control processing:
(4) Other embodiments:

(1) Configuration of color correction profile creation device:
FIG. 1 schematically shows the configuration of a computer that is a main part of a color correction profile creation apparatus according to an embodiment of the present invention. In FIG. 1, a computer 10 includes a bus 10a, through which a CPU 11, a ROM 12, a RAM 13, a hard disk drive (HDD) 14, a USB interface (I / F) 15, and a video interface (I / F) are connected. 16 are connected to each other. The HDD 14 stores an operation system (O / S) 14a and an image correction program 14b. The CPU 11 reads out the operation system O / S 14a and the image correction program 14b, and executes the processes described therein. At that time, the RAM 13 is used as a temporary storage area. A printer 30 and a colorimeter 40 are connected to the computer 10 via the USB I / F 15, and print data is printed by the printer 30, and a printed color chart is measured by the colorimeter 40. It is possible to do. In addition, a display 50 is connected to the computer 10 via a video I / F 16.

FIG. 2 conceptually shows the configuration of the program executed by the CPU 11. In the figure, O / S
P1 is executed, and the color correction profile creation program P2 and the driver P3 are executed on the O / S P1. The driver P3 operates the colorimeter 40 connected to the computer 10 and performs processing for obtaining colorimetric data from the colorimeter 40, and the color correction profile creation program P2 performs processing described later. O / S
P1 is interposed in each module constituting the driver P3 and the color correction profile creation program P2, and provides an interface between them.

  The color correction profile creation program P2 includes a target color acquisition unit P2a, a color conversion profile creation unit P2b, a color conversion unit P2c, a color chart printing unit P2d, a color correction profile creation unit P2e, and a print execution unit P2f. The target color acquisition unit P2a acquires a specific color in the first color space, and acquires a target color to be reproduced when the specific color is printed on the printing paper by the printer 30. Here, each color system used in the present embodiment will be described. The modules P2a to P2f constituting the color correction profile creation program P2 are not limited to those executed on the same computer 10 and may be executed on a plurality of computers.

  FIG. 3 shows an example in which the color correction profile creation program P2 is executed on a plurality of computers. In the figure, a color conversion profile creation computer (PC) 10a and a color correction profile creation computer (PC) 10b are individually provided, and the modules P2a to P2f are distributed in the PCs 10a and 10b. In the color conversion profile creation PC 10a, the color conversion profile creation unit P2b creates a color conversion profile, and the created color conversion profile is distributed to the color correction profile creation PC 10b. Then, using the distributed color conversion profile, the color correction profile P2c of the PC 10b for color correction profile creation creates a color correction profile. As described above, the functions of the color correction profile creation program P2 may be shared by the plurality of computers 10a and 10b.

  For example, when a printer manufacturer provides a genuine ICC profile for the printer 20, the printer manufacturer creates both a color conversion profile and a color correction profile using the computer 10 in FIG. Will be provided. On the other hand, when a user individually creates a color correction profile, the printer manufacturer uses the color conversion profile creation PC 10a shown in FIG. 3 to distribute only the color conversion profile to the user. Then, the user creates a color correction profile using the color correction profile creation PC 10b of FIG.

FIG. 4 schematically shows the relationship between the color systems. In the figure, the first color space is an L ^* a ^* b ^* color space which is a uniform color space. Since the correspondence between the L ^* a ^* b ^* color space and the sRGB color space used in the display or the like is defined by the ICC profile, what kind of color is absolutely displayed on the display 50? It can be specified in the L ^* a ^* b ^* color space whether it is a color. On the other hand, the second color space is an RGB color space, and the third color space is a CMYK color space. The CMYK color space is a device-dependent color space of the printer 30, and the space is defined around the ink color used by the printer 30.

The correspondence between the L ^* a ^* b ^* color space and the RGB color space is defined by the color correction profile. Note that the color correction profile is generally called a media profile in order to correct a color that varies depending on the printing paper. Furthermore, the correspondence between the RGB color space and the CMYK color space is defined by the color conversion profile. The color correction profile and the color conversion profile need only be able to specify the equal color relationship in each color space, and may be in a table format in which a plurality of representative colors corresponding to each color space are linked to each other. It may be a function format expressed by a generalized function.

As described above, since the color correction profile and the color conversion profile basically define the equal color relationship in each color space, it is necessary to prepare the color correction profile and the color conversion profile according to the printing paper in which the color of ink differs. In addition, the color correction profile and the color conversion profile basically define a color matching relationship in each color space, but it is possible to artificially correct these correspondences. For example, in the color correction profile, the input L ^* a ^* b ^* value is color-converted by applying correction that maps the L ^* a ^* b ^* value to the entire color gamut that the printer 30 can represent. When the part P2c converts the RGB value with reference to the color conversion profile, the converted RGB value can be output so as to make maximum use of the color gamut that the printer 30 can express.

  The color conversion unit P2c refers to the ICC profile, the color correction profile, and the color conversion profile, and performs color conversion on the input sRGB image data to CMYK image data. The color-converted CMYK image data is transferred to the print execution unit P2f, and processing for executing printing is performed in the print execution unit P2f. In this embodiment, since an inkjet printer 30 having CMYK ink is connected, the CMYK image data is converted into halftone data by the print execution unit P2f, and the halftone data is further converted into the ink ejection head. A process of rearranging according to the scanning order is performed. As a result, color printing can be performed by the printer 30. The color chart printing unit P2d provides image data for printing a color chart among image data to be printed by the printer 30.

(2) Color correction profile creation processing:
FIG. 5 shows the flow of target color acquisition processing that is executed in advance to create a color correction profile. In the present embodiment, processing for setting two types of target colors, paper gray mode and absolute gray mode, in the color correction profile will be described as an example. In step S100, the printer 30 is used to perform solid black printing on the printing paper for which a color correction profile is to be created. As described above, since it is necessary to create a color correction profile for each printing paper, black solid printing is performed on the printing paper for which the color correction profile is to be created. Specifically, the print execution unit P2f causes the printer 30 to execute solid black printing. Here, the black solid printing means printing in which a part or the whole of the printing paper is completely covered with the black ink used by the printer 30. Accordingly, the portion where the solid black printing is performed becomes the darkest color that the printer 30 can realize on the printing paper.

In step S110, the target color acquisition unit P2a acquires the color measurement value of the solid black print printed in step S100 from the colorimeter 40. In the present embodiment, a colorimetric value is acquired from the colorimeter 40 as a color coordinate value of the L ^* a ^* b ^* color space. Next, in step S120, the target color acquisition unit P2a acquires the colorimetric values of the same type of printing paper as the printing paper on which the black solid printing was performed in step S100 from the colorimeter 40. In the present embodiment, the expression “printing paper” means a printing paper of the same type as the printing paper on which solid black printing has been performed in step S100.

Similar to step S110, the colorimetric values of the paper are also obtained as the color coordinate values of the L ^* a ^* b ^* color space. In the printer 30 of the present embodiment, additive printing is performed in which ink is attached to white printing paper to form a printed image, so that the printer 30 can represent the printing paper on the printing paper. The brightest color. Through the above processing, the colorimetric values of the darkest color and the brightest color that can be expressed by the printer 30 on the printing paper are acquired as the color coordinate values of the L ^* a ^* b ^* color space. In step S130, the target color acquisition unit P2a acquires the target color in the paper gray mode based on these color coordinate values.

FIG. 6 illustrates the target color acquired in step S130. In the figure, an L ^* a ^* b ^* color space is shown. In the L ^* a ^* b ^* color space, the coordinate of the color measurement value of solid black printing is indicated by IB, and the color measurement value of the paper background is indicated by PW. Although IB depends on the color material of the black ink used by the printer 30, since the color material of the black ink is not strictly achromatic, the coordinates are shifted from the gray (a ^* = b ^* = 0) axis. . On the other hand, although PW depends on the printing paper, the color of the printing paper is not a strict achromatic color, so the coordinates are shifted from the gray (a ^* = b ^* = 0) axis.

In the paper gray mode, the target color is set on a straight line connecting IB and PW with a straight line in the L ^* a ^* b ^* color space. In FIG. 6, the color coordinate of the target color in the paper gray mode is denoted as G ₁ . Coordinates G ₁ in step S130 can be calculated by linear interpolation according to the lightness L ^* from the coordinates of PW and IB. In this way, by creating a gradation corresponding to the lightness for G ₁ on the line that linearly connects the brightest color and the darkest color that can be expressed by the printer 30 on the printing paper, it is not a strict achromatic color. It is possible to express natural gradation without color distortion between the brightest color and the darkest color.

In step S140, the target color acquisition unit P2a acquires the target color in the absolute gray mode. In FIG. 6, the target color of the color coordinates of the absolute gray mode is indicated as G _2. The locus of G ₂ passes through the coordinates of PW and IB, and only the lightness L ^* varies along the gray (a ^* = b ^* = 0) axis in the medium lightness region. By using such a locus of G ₂ , the brightest color and the darkest color that can be expressed by the printer 30 on the printing paper are expressed, but an achromatic color (a ^* = b) in the middle lightness region. A gradation corresponding to the lightness L ^{* of} G ₂ such that ^* = 0) can be reproduced. Note that, if target colors G ₁ and G ₂ are calculated for all lightness L ^* , the processing load increases. Therefore, here, for 17 lightness L ^{* s} that divide the lightness L ^* range into 16 equal parts, each of the target colors G ^* ₁ and G ₂ are calculated. The target colors G ₁ and G ₂ acquired as described above are stored in the HDD 14. When the target colors G ₁ and G ₂ are acquired, the color conversion profile creation unit P2b creates a color conversion profile. In this embodiment, the achromatic color G ₀ (a ^* = b ^* = 0) is a specific color so that the target colors G ₁ and G ₂ can be reproduced on the printing paper when the achromatic color G ₀ is printed. Create a color conversion profile and a color correction profile.

  FIG. 7 shows the flow of color conversion profile creation processing, and FIG. 8 schematically illustrates the color conversion profile creation processing. In step S200 of FIG. 7, the correspondence relationship between the RGB color space that is the second color space and the CMYK color space that is the third color space is calculated. Specifically, since RGB and CMY have a complementary color relationship, RGB-CMY correspondence can be calculated based on the complementary color relationship. Further, by performing a color separation process in which the common part of CMY is replaced with K, a CMY-CMYK correspondence can be obtained, and finally an RGB-CMYK correspondence can be obtained.

  In step S210, the color conversion profile creation unit P2b provisionally creates a color conversion profile in which RGB-CMYK correspondence is defined. The color conversion profile is a data table in which CMYK values corresponding to a plurality of representative grids in an RGB color space that are uniformly arranged are described based on the correspondence specified in step S200, and is stored in the HDD. In step S220, the color chart is printed by the printer 30. Specifically, the color conversion unit P2c acquires image data in which the color of each color patch is expressed in RGB, and the color conversion unit P2c refers to the color conversion profile and the image data is expressed in CMYK. Convert color to. Then, the print execution unit P2f causes the printer 30 to deposit CMYK ink on the printing paper with an ink amount substantially proportional to the value of CMYK.

As the color of each color patch, a color located on a uniform grid in the RGB color space is selected. In step S230, the color conversion profile creation unit P2b acquires the colorimetric values of the color chart from the colorimeter 40. Since the colorimetric values of the color chart are acquired as color coordinate values in the L ^* a ^* b ^* color space, the correspondence between the L ^* a ^* b ^* values, RGB values, and CMYK values for each color patch is specified. can do. In step S240, CMYK values are estimated such that the L ^* a ^* b ^* values become the target colors G ₁ and G ₂ when printed.

Since the correspondence between the L ^* a ^* b ^* value and the CMYK value is specified for each color patch color as described above, the target color represented by the L ^* a ^* b ^* value by performing linear interpolation or the like. CMYK values corresponding to G ₁ and G ₂ can be uniquely estimated. A CMYK value that can reproduce the target color G ₁ corresponding to the paper gray mode is expressed as CMYK _G1, and a CMYK value that can reproduce the target color G ₂ corresponding to the absolute gray mode is expressed as CMYK _G2. . As described above, the target colors G ₁ and G ₂ are calculated for the 17 lightness L ^* evenly distributed, and CMYK _G1 and CMYK _G2 are estimated for each of these. In step S250, CMYK values corresponding to RGB values satisfying R = G = B described in the color conversion profile are replaced with CMYK _G1 and CMYK _G2 , respectively.

FIG. 9 schematically shows how CMYK values corresponding to RGB values satisfying R = G = B can be replaced with CMYK _G1 and CMYK _G2 . On the left side of the figure, a color conversion profile before executing step S250 is shown. In the same color conversion profile, CMYK values based on complementary colors are described for each combination of RGB. On the other hand, on the right side of the figure, the color conversion profile after step S250 is shown. In the same color conversion profile, CMYK _G1 and CMYK _G2 are used for RGB values satisfying R = G = B, respectively. It has been rewritten.

In the color conversion profile of this embodiment, 17 sets of descriptions where RGB values satisfying R = G = B are (0, 0, 0), (16, 16, 16)... (255, 255, 255). CMYK _G1 and CMYK _G2 are associated only with these. That is, the RGB-CMYK correspondence relationship originally defined based on the complementary color relationship is corrected by CMYK _G1 and CMYK _G2 only for RGB values satisfying R = G = B. There are 17 sets of RGB (0, 0, 0), (16, 16, 16)... (255, 255, 255) satisfying R = G = B, and 17 sets of CMYK _G1 and CMYK _G2 are calculated. Therefore, these can be associated one-on-one according to the lightness L ^* . That is, if RGB values (0, 0, 0), (16, 16, 16)... (255, 255, 255) satisfying R = G = B also have a uniform brightness distribution in the range. Therefore, CMYK _G1 and CMYK _G2 of the corresponding lightness L ^* can be assigned in correspondence with the lightness.

In step S260, a header indicating that the color conversion profile creation unit P2b is in the paper gray mode is attached to the color conversion profile in which the CMYK values are replaced by CMYK _G1 . On the other hand, a header indicating that the color conversion profile creation unit P2b is in the absolute gray mode is attached to the color conversion profile in which the CMYK values are replaced by CMYK _G2 . With the above processing, a color conversion profile is determined, and a pair of paper gray mode and absolute gray mode color conversion profiles are created. When the color conversion profile is created as described above, a process for creating a color correction profile is executed next.

  FIG. 10 shows the flow of color correction profile creation processing. In the figure, in step S300, the color chart printing unit P2d acquires color chart image data. The color chart image data is specified by RGB values. In step S310, the user is inquired about whether to create a color correction profile for the paper gray mode or the absolute gray mode. When the paper gray mode is selected, the processing after step S320 is executed, and when the absolute gray mode is selected, the processing after step S325 is executed. First, a case where the paper gray mode is selected will be described. In step S320, the color conversion unit P2c converts the color chart image data acquired in step S300 into CMYK image data with reference to the paper gray mode color conversion profile. Since a header corresponding to each gray mode is attached to the color correction profile, it is possible to easily identify which gray mode the color correction profile is.

  By the way, it is desirable that the colors of the color patches formed on the color chart are evenly distributed in the entire RGB color space so that the print color can be verified over the entire color gamut. In addition, since a color close to an achromatic color is perceived sensitively, it is necessary to form many color patches near the achromatic color and accurately verify the print color. Therefore, a color chart in which the color patch colors are evenly distributed throughout the RGB color space and the color patch colors are provided near achromatic colors is a common color chart used to create a color correction profile. is there. Specifically, in order to form a color patch in the vicinity of an achromatic color, a large number of color patches satisfying R = G = B and a gray verification patch in which RGB values are slightly offset from R = G = B are provided. It becomes.

When the color conversion unit P2c performs color conversion on an RGB value whose correspondence is not defined in the color conversion profile, the CMYK value is specified by performing interpolation based on the correspondence relationship in which the RGB values are adjacent. Here, referring to the color conversion profile in the paper gray mode, when color conversion is performed for the color of the gray verification patch near R = G = B, CMYK associated with R = G = B in the color conversion profile. _G1 will be used for interpolation. That is, many color patches whose color conversion results are close to CMYK _G1 are formed. If the color conversion result is a value close to CMYK _G1 , the color measurement result of the color patch is expected to be a value approximate to the target color G ₁ in the L ^* a ^* b ^* color space.

In step S330, the print execution unit P2f causes the printer 30 to execute color chart printing. In step S <b> 340, the color measurement result of the printed color chart is acquired from the color measuring device 40. In step S350, the correspondence between the RGB value, the CMYK value, and the L ^* a ^* b ^* value obtained by the color measurement can be specified based on the color measurement result. That is, it is possible to specify what color of L ^* a ^* b ^* value is printed when printing is performed based on what RGB value. In step S360, a grid-like grid is generated in the first color space (L ^* a ^* b ^* color space), and the RGB values corresponding to the L ^* a ^* b ^* values on the grid points are generated in step S340. The color correction profile creating unit P2e describes the correspondence relationship of L ^* a ^* b ^* -RGB in the color correction profile.

With the above processing, a color correction profile that defines the correspondence relationship of L ^* a ^* b ^* -RGB is created. In step S370, an achromatic color L ^* a ^* b ^* among the lattice points is further created ^. value ^{(a * = b * = 0} ) the target color G ₁ is associate the RGB values that can be reproduced by the printing paper against. Specifically, the achromatic among the grid points L ^* a ^* b ^* values ^{(a * = b * = 0} ) and the brightness L ^* is the same target color G ₁ in FIG. 6 L ^* a ^* b ^* An RGB value corresponding to the target color G ₁ is specified by interpolation in the space, specified from the RGB-CMYK-L ^* a ^* b ^* correspondence relationship based on the color measurement result in step S340, and the specified RGB value is associated. As described above, since many color measurement results of the gray verification patches having L ^* a ^* b ^* values close to the target color G ₁ are obtained, color measurement is performed by performing interpolation based on the color measurement results. It is possible to accurately specify the RGB value for which the L ^* a ^* b ^* value obtained in this way is the target color G ₁ . Then, the RGB value corresponding to the accurately specified target color G ₁ is described in association with the achromatic L ^* a ^* b ^* value (a ^* = b ^* = 0). The body of the color correction profile is formed by the above processing, and in step S380, a header indicating that the color correction profile is in the paper gray mode is attached to the color correction profile.

On the other hand, when the absolute gray mode is selected, the color chart image data is color-converted with reference to the color conversion profile of the absolute gray mode in step S325. The image data of the color chart for performing color conversion is the same as that for performing color conversion in step S320. Steps S335 to S365 are the same as steps S330 to S360. However, absolute order with reference to gray mode color conversion profile is a color conversion of the image data of the color chart, L ^* a ^* b ^* values of the gray verification patch near colorimetry to the target color G ₂ in step S345 Many results will be obtained. By an absolute reference to the color conversion gray mode color conversion profiles, the paper gray mode to the target color G ₂ in the image data of the same color chart and L ^* a ^* b ^* values are close gray verification patch Can be reproduced. That is, it is not necessary to prepare different color charts for each of the target colors G ₁ and G ₂ , and it is possible to share a general-purpose color chart in which many gray color patches are formed.

Then, in step S375, associating RGB value corresponding to the target color G ₂ with respect to an achromatic color of L ^* a ^* b ^* values of the created color correction profile ^{(a * = b * = 0} ). Specifically, among the L ^* a ^* b ^* grid points defined in the color correction profile, the achromatic color L ^* a ^* b ^* value (a ^* = b ^* = 0) and the target color having the same lightness L ^* G ₂ is specified by interpolation in the L ^* a ^* b ^* space of FIG. 6, and an RGB value corresponding to the target color G ₂ is specified from the color measurement result in step S345 and associated. As described above, since many color measurement results of the gray verification patches having L ^* a ^* b ^* values close to the target color G ₂ are obtained, color measurement is performed by performing interpolation based on the color measurement results. L ^* a ^* b ^* values obtained Te can correctly identify the RGB values as the target color G _2.

Then, the RGB value corresponding to the accurately specified target color G ₂ is described in association with the achromatic L ^* a ^* b ^* value (a ^* = b ^* = 0). The body of the color correction profile is formed by the above processing, and in step S385, a header indicating that the color correction profile is in the absolute gray mode is attached to the color correction profile. In defining the correspondence relationship of L ^* a ^* b ^* -RGB in steps S360, S370, S365, and S375, in addition to artificial correction for the gray mode, color gamut adjustment, memory color correction, etc. May be performed incidentally. The paper gray mode and absolute gray mode color conversion profiles created by the color conversion profile creation processing, and the paper gray mode and absolute gray mode color correction profiles created by the color correction profile creation processing are stored in the HDD 14, and are respectively described above. This is used when printing is performed by the print control process.

(3) Print control processing:
FIG. 11 shows the flow of the print control process. The print control process shown in the figure is executed by the hardware shown in FIG. The paper gray mode and absolute gray mode color conversion profiles created in advance by the color conversion profile creation process, and the paper gray mode and absolute gray mode color correction profiles created by the color correction profile creation process are stored in the HDD 14. ing.

In step S400, image data to be printed is acquired. In step S410, the user is inquired whether to print the image data in the paper gray mode or the absolute gray mode. Then, the selected gray mode is specified according to the input operation from the user. If the paper gray mode is selected, in step S420, the color conversion unit P2c acquires a color conversion profile and a color correction profile to which a paper gray mode header is attached. At the same time, an ICC profile that defines the correspondence relationship of sRGB-L ^* a ^* b ^* shown in FIG. 4 is also acquired. In step S430, the color conversion unit P2c performs color conversion on the image data with reference to the color conversion profile, the color correction profile, and the ICC profile to which the paper gray mode header is attached.

The image data is expressed in sRGB, and the image data expressed in L ^* a ^* b ^* can be acquired by performing color conversion based on the ICC profile. Next, image data expressed in RGB can be acquired by performing color conversion on the image data expressed in L ^* a ^* b ^* based on the color correction profile. Furthermore, the image data expressed in CMYK can be acquired by performing color conversion on the image data expressed in RGB based on the color conversion profile. If the halftone data expressed in CMYK is output to the printer 30 in step S440, the amount of each ink in the printer 30 can be specified, so that the print image can be reproduced on the printing paper in step S450.

L ^* a ^* b ^* achromatic or Ryakuna colored pixels in the image data converted into color system (a ^* ≒ b ^* pixel satisfying the ≒ 0), the color conversion profile and color correction profile paper gray mode By performing color conversion with reference to FIG. 6, a linear color change is caused according to lightness as shown in FIG. 6. When creating a paper gray mode color conversion profile and color correction profile, a specific color that is an achromatic color (a ^* = b ^* = 0) is used as the target color of paper gray having a linear color change according to the lightness. This is because they are associated. Therefore, when the user selects the paper gray mode, a gray gradation without color twist can be reproduced.

On the other hand, when the absolute gray mode is selected, in step S425, the color conversion unit P2c acquires a color conversion profile and a color correction profile to which an absolute gray mode header is attached. At the same time, an ICC profile that defines the correspondence relationship of sRGB-L ^* a ^* b ^* shown in FIG. 4 is also acquired. In step S435, the color conversion unit P2c performs color conversion on the image data with reference to the color conversion profile, the color correction profile, and the ICC profile to which the absolute gray mode header is attached. By performing color conversion with reference to the color conversion profile and the color correction profile in the absolute gray mode, it is possible to reproduce a colorimetrically accurate achromatic color at medium lightness as shown in FIG.

  In the color conversion profile creation process, it is possible to create a color correction profile with high accuracy by creating a color conversion profile and a color correction profile in association with each other according to the gray mode. The color conversion profile and color correction profile created in this way need to be used in combination with the corresponding ones when color-converting and printing image data. Therefore, the color conversion profile and the color correction profile can be matched by attaching a header for specifying the gray mode to the color conversion profile and the color correction profile as in this embodiment.

(4) Other embodiments:
In the color correction profile of the present invention, only the region corresponding to the specific color among the specified color regions is corrected to the correspondence relationship according to the target color. In the example of the previous embodiment, only the correspondence relationship for the gray region (R = G = B) in the color correction profile differs depending on the target color (paper gray, absolute gray). Accordingly, only the gray region (R = G = B) can be regarded as a variable region in which the correspondence relationship varies according to the target color, and the other high-saturation regions can be regarded as invariable regions having a constant correspondence relationship regardless of the target color. . Accordingly, it is possible to prepare a correspondence relationship according to the target color only for the variable region and to make the correspondence relationship common to the other invariant regions.

  FIG. 12 shows an invariant table that defines the correspondence between the invariant areas in the color conversion profile, and a variable table that defines the correspondence between the variable areas in the color conversion profile for each target color (paper gray, absolute gray). Is shown. In the figure, the invariant table T1 describes the correspondence other than the gray area (R = G = B), and the variable tables T2a and T2b describe the correspondence of the gray area (R = G = B). Yes. The correspondence defined in the variable tables T2a and T2b corresponds to the paper gray mode and the absolute gray mode, respectively, and both are independent tables. The variable tables T2a and T2b are attached with headers indicating that they are in the paper gray mode and the absolute gray mode, respectively.

  For example, when the target color (paper gray, absolute gray) is specified in the print control process, the gray area is color-converted with reference to the invariant table T1, and the gray area is selected. Color conversion may be performed by referring to the variable tables T2a and T2b to which the target color header is attached. In this way, color conversion can be performed over the entire RGB color space, and different color conversions can be performed according to the target color. In addition, since it is not necessary to store the correspondence relationship individually for an area where the correspondence relationship is constant regardless of the target color, the capacity of the entire color conversion profile can be reduced.

Since the color conversion profile and the color correction profile created according to the present invention correspond to each other according to the target color, they may be combined when performing color conversion with reference to these. For example, by combining a paper gray mode color conversion profile and a color correction profile, L ^* a ^* b ^* -CMYK color conversion can be performed collectively without going through the RGB color system. Needless to say, sRGB-CMYK color conversion may be collectively performed by combining an ICC profile such as a display. In this way, the capacity for storing each profile can be reduced, the number of color conversion steps can be reduced, and the processing speed can be increased. Note that the color conversion profile and the color correction profile only need to be able to define the correspondence between the respective color spaces, and may be created as a table as in the above embodiment, or a conversion formula may be prepared.

  Furthermore, in the above-described embodiment, an example in which a plurality of target colors are set for the achromatic color as the specific color is illustrated, but the specific color and the target color may be set for other colors. For example, a color constituting the sepia image may be set as a specific color, and a target color corresponding to the user's preference may be set for the specific color. By doing so, it is possible to output a sepia image according to the user's preference. It is also possible to create color conversion profiles and color correction profiles that can convert monochrome image data to sepia image data by setting achromatic colors as specific colors and colors that make up sepia images as target colors. It is.

It is a hardware block diagram of the color correction profile production apparatus concerning one Embodiment of this invention. It is a software block diagram of a color correction profile creation apparatus. It is a software block diagram of a color correction profile creation apparatus. It is a figure which shows the relationship of a color space. It is a flowchart which shows a target color setting process. It is a graph explaining a target color. It is a flowchart which shows a color conversion profile creation process. It is a schematic diagram explaining a color conversion profile creation process. It is a table | surface which shows a color conversion profile. It is a flowchart which shows a color correction profile creation process. 6 is a flowchart illustrating print control processing. It is a table | surface which shows the color conversion profile concerning a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Computer, 10a ... Bus, 11 ... CPU, 12 ... ROM, 13 ... RAM, 14 ... HDD, 14a ... O / S, 14b ... Color correction profile creation program, 15 ... USB I / F, 16 ... Video I / F , 30 ... Printer, 40 ... Colorimeter, 50 ... Display, P1 ... O / S, P2 ... Color correction profile creation program, P2a ... Target color acquisition unit, P2b ... Color conversion profile creation unit, P2c ... Color conversion unit, P2d ... Color chart printing unit, P2e ... Color correction profile creation unit, P2f ... Print execution unit

Claims (7)

In a color correction profile creation device that creates a color correction profile that defines the correspondence between the first color space and the second color space,
Target color acquisition means for acquiring a target color to be reproduced on the printing paper by the specific color in the first color space;
A profile that defines a correspondence relationship between the second color space and the third color space,
When the color chart is printed on the printing paper while performing color conversion with reference to the profile, the correspondence relationship is such that a color patch having substantially the same color as the target color acquired in advance is reproduced. Color conversion profile creation means for creating a corrected color conversion profile;
Color chart printing means for printing the color chart on the printing paper while performing color conversion with reference to the color conversion profile;
Color correction profile creating means for creating the color correction profile that associates the specific color with the color coordinates in the second color space where the target color can be reproduced based on the color measurement result of the color chart. A color correction profile creation device characterized by: The above color conversion profile includes
In accordance with the target color, a variable region in which the correspondence relationship between the second color space and the third color space is corrected so that a color patch having substantially the same color as the target color is reproduced,
The color correction profile creating apparatus according to claim 1, further comprising an invariant region in which the correspondence relationship is constant regardless of the target color. The specific color is an achromatic color of each brightness in the first color space,
2. The target color corresponding to each lightness achromatic color is a color having a linear color change between a brightest color and a darkest color that can be expressed on the printing paper. Or the color correction profile production apparatus in any one of Claim 2. The specific color is an achromatic color of each brightness in the first color space,
4. The color correction profile creation device according to claim 1, wherein the target color corresponding to each lightness achromatic color is an achromatic color of each lightness on the printing paper. In the color correction profile creation method for creating a color correction profile that defines the correspondence between the first color space and the second color space,
A target color acquisition step of acquiring a target color to be reproduced on the printing paper by the specific color in the first color space;
A profile that defines a correspondence relationship between the second color space and the third color space,
When the color chart is printed on the printing paper while performing color conversion with reference to the profile, the correspondence relationship is such that a color patch having substantially the same color as the target color acquired in advance is reproduced. A color conversion profile creation step for creating a corrected color conversion profile;
A color chart printing step of printing the color chart on the printing paper while performing color conversion with reference to the color conversion profile;
A color correction profile creating step for creating the color correction profile that associates the specific color with the color coordinates in the second color space where the target color can be reproduced based on the color measurement result of the color chart; A color correction profile creating method comprising: In a color correction profile creation program for causing a computer to execute a function of creating a color correction profile that defines the correspondence between the first color space and the second color space,
A target color acquisition function for acquiring a target color to be reproduced on the printing paper by the specific color in the first color space;
A profile that defines a correspondence relationship between the second color space and the third color space,
When the color chart is printed on the printing paper while performing color conversion with reference to the profile, the correspondence relationship is such that a color patch having substantially the same color as the target color acquired in advance is reproduced. A color conversion profile creation function for creating a corrected color conversion profile;
A color chart printing function for printing the color chart on the printing paper while performing color conversion with reference to the color conversion profile;
A color correction profile creation function for creating the color correction profile that associates the specific color with the color coordinates in the second color space where the target color can be reproduced based on the color measurement result of the color chart; A color correction profile creation program which is executed by a computer. In a printing control device that executes printing on printing paper in a printing device while converting image data expressed in the first color space into image data expressed in the third color space,
Target color acquisition means for acquiring a target color to be reproduced on the printing paper by the specific color in the first color space;
A profile that defines a correspondence relationship between the second color space and the third color space, and a color chart is printed on the print paper while performing color conversion with reference to the profile. A color conversion profile acquisition means for acquiring a color conversion profile in which the correspondence relationship is corrected so that a color patch having substantially the same color as the target color acquired in advance is reproduced;
A profile that defines a correspondence relationship between the first color space and the second color space, based on the color measurement result of the color chart printed while performing color conversion with reference to the profile. Color correction profile acquisition means for acquiring a color correction profile that associates the specific color with the color coordinates in the second color space where the target color can be reproduced;
The image data expressed in the first color space based on the correspondence relationship between the first color space and the third color space defined by the color correction profile and the color conversion profile Color conversion means for converting into image data expressed in three color spaces;
A printing control apparatus comprising: a printing execution unit that causes the printing apparatus to execute printing based on the image data converted by the color conversion unit.

Images