JP4875503B2 - Color conversion definition creation device and color conversion definition creation program - Google Patents

Description

  The present invention relates to a color conversion definition creating apparatus and a color conversion definition creating program for creating an N color conversion definition that defines a correspondence relationship between coordinates in an N-dimensional first color space and coordinates in a predetermined second color space.

  In recent years, with the development of information technology, image information is often converted into electronic data and handled as image data, and image output devices such as displays, projectors, and printers that output images based on the image data have become widespread. In particular, in the case of color images, technology for processing and editing image data representing color images on computers has advanced, and output of processed and edited images to color printers has become increasingly popular. ing.

  In the image output device, even if the images are output based on the same image data, the color of the image may differ depending on the type of the image output device. For example, a color printer often outputs a color image based on image data representing four colors of C (cyan), M (magenta), Y (yellow), and K (black). Even when two color printers output color images based on CMYK image data, the obtained color images may have different hues. Other color-dependent methods depending on the device, such as the CMY color system or the CMYK color system in which K (black) is added to CMY, include R (red), G (green), and B ( A color system using three colors (blue) is well known, and is often used as image data for display.

  In many image output devices, each image output device is represented in a device-dependent color space such as CMYK or RGB so that the output target color matches the color that is actually output. A profile (color conversion definition) representing the correspondence between color coordinates and color coordinates represented in a device-independent color space such as L * a * b * and XYZ is prepared. By using this profile, when the output target color is expressed as the coordinate value of the device-independent color space, the coordinate value in the device-dependent color space corresponding to the coordinate value can be obtained. It becomes. Then, by using the obtained coordinate value as an output set value, it is possible to make the output target color coincide with the actually output color. Here, in many cases, the profile is a discrete coordinate point of the device-dependent color space (for example, lattice points arranged at equal intervals in the space) and device-independent corresponding to these coordinate points. The color conversion table format is one-to-one with the coordinate points of the colors represented in the color space.

As a profile creation method, for example, in the case of a color printer using CMYK, first, output is performed for several coordinate points in the CMYK color space while changing the halftone dot area ratio (halftone%) which is the coordinate component of the CMYK color space. To obtain device-independent values (for example, XYZ values) corresponding to the respective coordinate points by colorimetry using the colorimeter, and then output among the discrete coordinate points constituting the profile. For the remaining coordinate points excluding the coordinate points that have been subjected to the above, a creation method that takes two steps, such as calculating device-independent values corresponding to the remaining coordinate points by interpolation calculation, may be employed. Recently, as an interpolation calculation when creating a profile, a Laplace equation in the form of a difference (simultaneous equations defined on a discrete space, which results in a Laplace equation in continuous space when taking the continuous limit) A method has been proposed in which an unknown device-independent value is obtained by using an interpolation formula and solving a Laplace equation in the difference format using a known device-independent value as a boundary condition (see, for example, Patent Document 1).
JP 2006-24971 A

  Many color printers are provided with four colors of CMYK toners, and various colors are expressed by combining these colors. In recent years, color printers having high color expression ability that have toners of Or (orange) and G (green) in addition to these four colors have appeared. Even in such a color printer having five or more colors, it is possible in principle to create a profile by color measurement by the colorimeter and interpolation calculation as described above. If the number of color types is 5, there is not much trouble with the required colorimetry, but as the number of color types increases as 6 colors, 7 colors, etc., the combination of colors to be measured increases. Therefore, the labor for color measurement increases, and the labor required for creating a profile cannot be ignored.

  In view of the above circumstances, an object of the present invention is to provide a color conversion definition creating apparatus and a color conversion definition creating program that are suitable for reducing labor required for creating a color conversion definition.

In order to achieve the above object, the color conversion definition creating apparatus of the present invention provides:
For a first color space having coordinates that correspond to the colors obtained by using different N colors as color components within a predetermined upper limit as coordinates, the coordinates of the first color space and the predetermined color A color conversion definition creation device for creating an N color conversion definition that defines a correspondence relationship with coordinates in a second color space,
The coordinates of the third color space having the coordinate axes corresponding to each of the M colors, representing the coordinates obtained by using a part of the M colors (M <N) within the above upper limit as color components. The M color conversion definition that defines the correspondence between the coordinates of the second color space and the coordinates of the second color space is a combination of a plurality of M colors in which the combination of the M colors is different from each other and each of the N colors is included in any combination. An acquisition unit configured to acquire each of a plurality of third color spaces corresponding to each combination;
The first color space defined by the N color conversion definition using the correspondence relationship between the coordinates of the third color space defined by each M color conversion definition acquired by the acquisition unit and the coordinates of the second color space. Among the coordinates of the coordinates of the second color space and the coordinates of the first color space where the color component of the color not included in the M color corresponding to the third color space is zero. A response determination unit;
An estimation unit that estimates a correspondence in a vertex whose correspondence is not yet determined in the correspondence determination unit among the vertices of the first color space based on a correspondence in a vertex whose correspondence is determined in the correspondence determination unit;
Interpolation calculation for obtaining a correspondence relationship in a coordinate whose relationship is undetermined among coordinates in the first color space based on the correspondence relationship determined by the correspondence determination unit and the correspondence relationship estimated by the estimation unit. And a section.

  The color conversion definition creating apparatus of the present invention simply estimates the correspondence relationship at the vertex for which the correspondence relationship is undetermined, and calculates the correspondence relationship at the remaining coordinates whose correspondence relationship is undetermined by interpolation calculation. For this reason, the color conversion definition creating apparatus of the present invention can obtain a high-dimensional profile by synthesizing low-dimensional profiles with less labor for colorimetry, and is suitable for reducing labor required for creating color conversion definitions. Yes.

  In the present invention, various forms corresponding to various known interpolation calculation methods can be considered. In the color conversion definition creating apparatus of the present invention, “the interpolation calculation unit corresponds to the correspondence relationship among the ridge lines of the first color space. Is obtained by solving a one-dimensional Laplace equation using the correspondence at the end points of each ridge line as a boundary condition for the ridge line having undecided coordinates, and surrounding by the ridge line in the first color space. Among the two-dimensional surfaces surrounded by the two-dimensional surface having the coordinates whose correspondence is undetermined, the correspondence relationship in the coordinates on each two-dimensional surface is the correspondence relationship in the coordinates on the edge surrounding each two-dimensional surface. As a boundary condition, it is obtained by solving a two-dimensional Laplace equation, and the correspondence obtained by solving the Laplace equation is further set as a new boundary condition. The process of solving up the Laplace equation, by solving the final N-dimensional Laplace equation is repeated while increasing successively dimensions, form of the is "intended to complete the N color conversion definition are a preferred form.

  According to such a form, the problem of creating an N color conversion definition results in a boundary value problem of a so-called Laplace equation, and an N color conversion definition is uniquely obtained by solving this boundary value problem. .

  In the color conversion definition creating apparatus of the present invention, the form “the second color space is a device-independent color space” is a preferred form.

  According to such a form, when the user uses a plurality of types of devices in combination, it is possible to combine the color conversion definitions for the respective devices.

In order to achieve the above object, the color conversion definition creating program of the present invention provides:
Built into a computer system,
For a first color space having coordinates that correspond to the colors obtained by using different N colors as color components within a predetermined upper limit as coordinates, the coordinates of the first color space and the predetermined color A color conversion definition creating program for creating an N color conversion definition defining a correspondence relationship with coordinates in a second color space,
On that computer system,
The coordinates of the third color space having the coordinate axes corresponding to each of the M colors, representing the coordinates obtained by using a part of the M colors (M <N) within the above upper limit as color components. The M color conversion definition that defines the correspondence between the coordinates of the second color space and the coordinates of the second color space is a combination of a plurality of M colors in which the combination of the M colors is different from each other and each of the N colors is included in any combination. An acquisition unit configured to acquire each of a plurality of third color spaces corresponding to each combination;
The first color space defined by the N color conversion definition using the correspondence relationship between the coordinates of the third color space defined by each M color conversion definition acquired by the acquisition unit and the coordinates of the second color space. Among the coordinates of the coordinates of the second color space and the coordinates of the first color space where the color component of the color not included in the M color corresponding to the third color space is zero. A response determination unit;
An estimation unit that estimates a correspondence in a vertex whose correspondence is not yet determined in the correspondence determination unit among the vertices of the first color space based on a correspondence in a vertex whose correspondence is determined in the correspondence determination unit;
Interpolation calculation for obtaining a correspondence relationship in a coordinate whose relationship is undetermined among coordinates in the first color space based on the correspondence relationship determined by the correspondence determination unit and the correspondence relationship estimated by the estimation unit. It is characterized by building a part.

  By executing the color conversion definition creating program of the present invention in a computer system, the color conversion definition creating apparatus of the present invention can be easily realized.

  It should be noted that the color conversion definition creation program referred to in the present invention is only shown in its basic form here, but this is merely for avoiding duplication, and the color conversion definition creation program referred to in the present invention includes the above-described color conversion definition creation program. In addition to the basic form, various forms corresponding to each form of the color conversion definition creating apparatus described above are included.

  Furthermore, the elements such as the estimation unit that the color conversion definition creation program of the present invention constructs on the computer system may be constructed such that one element is constructed by one program part, and one element is a plurality of programs. It may be constructed by parts, or a plurality of elements may be constructed by one program part. In addition, these elements may be constructed so as to execute such an action by themselves, or may be executed by giving instructions to other programs and program components incorporated in the computer system. It may be constructed.

  According to the present invention, the labor required for creating a color conversion definition is reduced.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an image output system to which an embodiment of the present invention is applied.

  This image output system has a personal computer 20 and a color printer 30 and outputs an image 31 from the color printer 30 under the control of the personal computer 20. The personal computer 20 receives image data generated by reading an image with a color scanner (not shown). Here, the input image data is image data represented by three color components of C (cyan), M (magenta), and Y (yellow) depending on the device. The personal computer 20 includes CMY image data generated by reading an image with a color scanner, and device-independent XYZ tristimulus values obtained when the image is measured by the spectrocolorimeter 40. The input characteristics (input profile) of the color scanner, which defines the correspondence relationship with the image data represented by (2), is stored in advance, and the personal computer 20 uses the input CMY image data based on the input profile. Then, the image represented by the image data is converted into image data represented by XYZ tristimulus values. When the personal computer 20 causes the color printer 30 to output an image, the color of the output image is represented by the above-described XYZ tristimulus values so that it matches the color of the image read by the color scanner. The converted image data is converted based on the above input profile and output characteristics (output profile) of the color printer 30 created by the method described later, and the converted image data is sent to the color printer 30. The color printer 30 includes toners of C (cyan), M (magenta), Y (yellow), K (black), Or (orange), and G (green). The above-mentioned image data sent from the personal computer 20 to the color printer 30 designates how much each of the above six colors the color printer 30 should output by a halftone dot area ratio (hereinafter referred to as halftone). The color printer 30 outputs data 31 based on the sent image data.

  Prior to outputting the image 31, the personal computer 20 creates an output profile for the color printer 30. The output profile is created through the following two steps.

  In the first stage of the output profile creation, an output profile defining the relationship between the CMYKOr five colors and the XYZ tristimulus values when the G component is not used, and the CMYKG 5 when the Or component is not used. An output profile defining the relationship between colors and XYZ tristimulus values is created. When creating these output profiles, the personal computer 20 outputs chart data for each of the five colors CMYKOr and CMYKG representing the chart 32 in which a plurality of patches are arranged to the color printer 30. The color printer 30 outputs a chart 32 according to the chart data, and the color of the patches constituting the chart 32 is measured by the spectrocolorimeter 40 to obtain XYZ tristimulus values representing each of the plurality of patches. . The above two output profiles are obtained from the chart data and the XYZ measurement data obtained by the spectrocolorimeter 40 for each of the five colors CMYKOr and CMYKG.

  In the second stage of creating the output profile, these two output profiles are synthesized to create a synthesized profile that defines the relationship between the six colors CMYKOrG and the tristimulus values XYZ.

  A feature of the image processing system as an embodiment of the present invention lies in the creation of a composite profile executed by the personal computer 20, and the personal computer 20 is an embodiment of the color conversion definition creating apparatus of the present invention. Works as. Hereinafter, the personal computer 20 will be described in detail.

  2 is an external perspective view of the spectrocolorimeter 40 and the personal computer 20 shown in FIG. 1, and FIG. 3 is a hardware configuration diagram of the personal computer 20. As shown in FIG.

  When the color of the chart 32 is measured, the chart 32 is placed on the spectrocolorimeter 40 as shown in FIG. 2, and the plurality of patches arranged on the chart 32 are measured by the spectrocolorimeter 40. Is done. The measured value of each patch obtained by the measurement is input to the personal computer 20 via the cable 41.

  The personal computer 20 has an appearance configuration, a main body device 21, an image display device 22 that displays an image on a display screen 22a in accordance with an instruction from the main body device 21, and a main body device 21 in accordance with various key operations. A keyboard 23 for inputting information and a mouse 24 for inputting an instruction corresponding to, for example, an icon or the like displayed at that position by designating an arbitrary position on the display screen 22a are provided. The main body device 21 has an FD loading port 21a for loading a flexible disk (FD) and a CD-ROM loading port 21b for loading a CD-ROM.

  As shown in FIG. 3, the main body device 21 includes a CPU 211 that executes various programs, a main memory 212 that is read out by a program stored in the hard disk device 213 and developed for execution by the CPU 211, and various programs. And the hard disk device 213 in which data and data are stored, the FD drive 214 loaded with the flexible disk 50 and accessing the loaded flexible disk 50, the CD-ROM 51 are loaded, and the CD-accessing the loaded CD-ROM 51 An input / output interface 216 that receives colorimetric data from the ROM drive 215 and the spectrocolorimeter 40 (see FIGS. 1 and 2) and sends image data to the color printer 30 (see FIG. 1) is built-in. Elements, and also the image display 22 shown in FIG. Keyboard 23, mouse 24 are connected to each other via a bus 25.

  Next, an embodiment of the color conversion definition creating program of the present invention will be described.

  When an embodiment of the color conversion definition creating program of the present invention is stored in, for example, the CD-ROM 51, when the CD-ROM 51 is loaded into the main body device 21 from the CD-ROM loading slot 21b, The color conversion definition creation program stored in the CD-ROM 51 is installed in the hard disk device 213 of the personal computer 20 by the CD-ROM drive 215. When the color conversion definition creation program installed in the hard disk device 213 is activated, the personal computer 20 operates as an embodiment of the color conversion definition creation device of the present invention.

  FIG. 4 is a diagram showing an embodiment of the color conversion definition creating program of the present invention.

  Here, the color conversion definition creating program 60 is stored in the CD-ROM 51. The storage medium storing the color conversion definition creating program 60 according to the present invention is not limited to the CD-ROM 51 shown in FIG. 4 but also the hard disk device 213 and FD 2140 shown in FIG. Various storage media such as the illustrated DVD and MO can be employed.

  The color conversion definition creation program 60 is executed in the personal computer 20 shown in FIGS. 2 and 3, and operates the personal computer 20 as an embodiment of the present invention as described above. , A setting unit 62, an estimation unit 63, and a calculation unit 64.

  Detailed contents of each element of the color conversion definition creating program 60 will be described later.

  FIG. 5 shows an outline of elements constructed on the personal computer for operating the personal computer shown in FIGS. 2 and 3 as an embodiment of the color conversion definition creating apparatus of the present invention, and an action by these elements. FIG.

  When the color conversion definition creation program 60 shown in FIG. 4 is installed in the personal computer 20 shown in FIGS. 2 and 3, each element of the acquisition unit 71, setting unit 72, estimation unit 73, and calculation unit 74 shown in FIG. Is constructed on the personal computer 20. With these elements, the personal computer 20 operates as an embodiment of the color conversion definition creating apparatus of the present invention. The acquisition unit 71, the setting unit 72, the estimation unit 73, and the calculation unit 74 are respectively connected to the personal computer by the acquisition unit 61, the setting unit 62, the estimation unit 63, and the calculation unit 64 in the color conversion definition creation program 60 shown in FIG. 20 is built on top. Therefore, each element in FIG. 4 corresponds to each element in FIG. 5, and each element in FIG. 5 includes the hardware of the personal computer 20 shown in FIGS. 2 and 3 and the OS and application executed on the personal computer 20. 4 is different from the first embodiment in that each element of the color conversion definition creating program 60 shown in FIG. 4 is configured only by the application program. Here, the acquisition unit 71 corresponds to an example of an acquisition unit according to the present invention, and the setting unit 72 corresponds to an example of a correspondence determination unit according to the present invention. The estimation unit 73 corresponds to an example of the estimation unit according to the present invention, and the calculation unit 74 corresponds to an example of the interpolation calculation unit according to the present invention. Below, each element shown in FIG. 5 and the outline of the effect | action by each element are demonstrated.

  The acquisition unit 71 is a profile that defines the relationship between CMYKOr five colors and XYZ tristimulus values when the G component is not used, and CMYKG five colors and XYZ tristimulus values when the Or component is not used. Get a profile that defines the relationship with. These profiles are obtained by dividing each of the five color spaces with a grid and XYZ tristimulus values corresponding to the grid points (that is, five mesh% giving the coordinates of the grid points). XYZ tristimulus values corresponding to a set of numerical values) are arranged in a one-to-one correspondence (table) format. Hereinafter, such a table is referred to as a color conversion table. Such grid points may be, for example, points arranged at equal intervals (for example, in 10% increments) for each color, but in the following, the grid intervals are different for each color, and even the same color. The discussion will proceed assuming that the lattice spacing differs depending on the position of the lattice spacing. The reason for taking a lattice in which the lattice spacing differs according to the size of the halftone value is as follows.

  When an image is output by the color printer 30, the corresponding XYZ tristimulus values may change nonlinearly depending on the position of the grid point due to the influence of dot gain or the like. Therefore, the computer 20 shown in FIG. 2 and FIG. 3 employs a method of taking grid points such that the grid interval is narrow in such a region with high non-linearity. Can be created.

In the color conversion tables of the two output profiles described above, the halftone value of each color is 0% or 100% in each color conversion table because it is used as a boundary condition in the differential decomposition method described later. The points are assumed to be adopted as grid points. For example, in the color conversion table of the output profile that defines the relationship between the five CMYKOr colors and the XYZ tristimulus values when the G component is not used, the halftone values of the five CMYKOr colors are 100% and 100%, respectively. 100%, 0%, 100%, 100%, 0%, 0%, 100%, 100%, etc. are all adopted as grid points. In this way, the halftone value of each color is 0% or 100%. Since two kinds of halftone values of 0% or 100% can be selected for each of the five colors, 2 ⁵ = 32 in total. Exists.

  In the color conversion tables of the above two output profiles, the four colors of CMYK are common. For simplicity, the method of taking grid points in the color space of CMYK between these two color conversion tables is here. The discussion will proceed as if the (lattice arrangement) is common. However, as will be described later, it is possible to create a color conversion table of a composite profile even when the method of taking grid points is not common.

  On the other hand, the composite profile is a table (table) in which each grid point when the CMYKOrG6 color space is partitioned by a grid and the XYZ tristimulus values corresponding to each grid point are arranged in a one-to-one correspondence. It has the form of Therefore, the composite profile creation operation specifically represents the XYZ tristimulus values corresponding to the respective grid points in the 6% halftone color space of CMYKOOrG based on the above two color conversion tables. Means to create a color conversion table. At this time, the above two color conversion tables indicate the tristimulus values corresponding to the respective lattice points in the five-dimensional subspace in which the Or or G component is 0% in the 6% halftone color space. Represents. In creating the color conversion table of the composite profile, the setting unit 72 has already obtained the corresponding XYZ tristimulus values from the above two color conversion tables among the grid points of the 6% halftone color space. The following grid points are processed as follows.

  When the grid points for which the corresponding XYZ tristimulus values have already been determined are duplicated in the two color conversion tables, the average value of the XYZ tristimulus values is converted into the color conversion of the composite profile. Set to the corresponding location in the table. When the grid point for which the XYZ tristimulus values are determined exists only in one color conversion table, the XYZ tristimulus values are set in corresponding positions in the color conversion table of the composite profile.

  The estimation unit 73 has a mesh% of 0% or 100% for the four colors of CMYK among the grid points of the 6% mesh% color space, and the network% values of the Or component and the G component are both 100%. The corresponding XYZ tristimulus values are estimated for the lattice points. The calculation unit 74 performs interpolation calculation based on the estimation result of the estimation unit 73 to complete the color conversion table of the composite profile.

  Hereinafter, the synthesis of two five-color color conversion tables will be described in detail.

  FIG. 6 is a flowchart showing the operation when the color conversion table is synthesized by the personal computer 20.

  First, by the acquisition unit 71 shown in FIG. 5, the above two color conversion tables, that is, the GMY of 5 colors of CMYKOr and the tristimulus values of XYZ when the G component is not used as an object of synthesis processing. And a color conversion table that defines the relationship between the half-tone CMYKG colors and the XYZ tristimulus values when the Or component is not used (step S11). Here, when the G component is not used, the relationship between the CMYKOr five-color half-tone and the XYZ tristimulus values is as follows. In the CMYKOrG six-color half-value space, the G component half-% is 0%. This corresponds to the relationship between the remaining CMYKOr five-color halftone% and the XYZ tristimulus values. Similarly, when the Or component is not used, the relationship between the CMYKG five-color halftone and the XYZ tristimulus values is as follows. In the CMYKORG six-color half-value space, the Or component halftone is 0%. This corresponds to the relationship between the halftone C% of the colors of CMYKG and the tristimulus values of XYZ. At this time, in the space of the halftone value of 6 colors of CMYKOOrG, the grid point where both the halftone percentage of the G component and the Or component is 0% must exist in common in the two color conversion tables. However, when combining the color conversion tables, the setting unit 72 shown in FIG. 5 determines the XYZ values corresponding to the respective lattice points from the two color conversion tables for the lattice points common to the two color conversion tables. Each is read, and the average value is written in the corresponding location in the color conversion table of the composite profile (step S12).

  If the two five-color color conversion tables do not share the same CMYK color space grid point setting method, the setting unit 72 performs interpolation calculation based on the five-color color conversion table. Then, the XYZ values corresponding to the respective grid points in the six-color halftone color space are calculated. Then, the calculated XYZ value is written in the corresponding location in the color conversion table of the composite profile.

  The setting unit 72 writes the portion of the two color conversion tables that exists only in one color conversion table into the corresponding portion in the color conversion table of the composite profile as it is (step S13). . For example, the data of XYZ values corresponding to the grid points where the dot percentage of the Or component is 0% but the dot percentage of the G component is not 0% are the CMYKG five colors of the above two color conversion tables. It exists only in the color conversion table that defines the relationship between halftone% and XYZ tristimulus values. Similarly, the data of the XYZ values corresponding to the grid points where the halftone% of the G component is 0% but the half% of the Or component is not 0% are the above two color conversion tables. Among the color conversion tables, it exists only in the color conversion table that defines the relationship between the halftone CMYKOr color% and the XYZ tristimulus values. The setting unit 72 writes the XYZ value data that exists only in one of these color conversion tables to the corresponding location in the color conversion table of the composite profile.

  In the process up to step S13, the grid points of the six color spaces of CMYKORG for which the corresponding XYZ values have not yet been obtained are the grid points at which neither the network% value of the Or component nor the G component is 0%. It is. Hereinafter, a method for obtaining XYZ values corresponding to these lattice points will be described.

The estimation unit 73 in FIG. 5 corresponds to a grid point in which the halftone values of the four colors of CMYK are 0% or 100% and the halftone values of both the Or component and the G component are 100%. The XYZ value is estimated by the method described below (step S14). In this way, there are 2 ⁴ = 16 lattice points in total, because the grid point values of the four colors of CMYK are 0% or 100%, and the same estimation is made for each lattice point. Done.

  In executing the estimation, the estimation unit 73 in FIG. 5 has a mesh% value common to the grid point to be estimated for the CMYK four-color halftone values, and both the network of both the Or component and the G component. As for the% value, the XYZ value corresponding to the lattice point O is read from the numerical values already written in the composite color conversion table for the lattice point (lattice point O) which is 0%. Next, the estimation unit 73 regards the CMYKG five-color halftone values as the XYZ values corresponding to the lattice point P having the same halftone value as that of the lattice point O and the halftone value of the Or component being 100%. , The XYZ values corresponding to the lattice point Q having the same halftone value as the lattice point O and the halftone value of the G component being 100% are obtained from the composite color conversion table. read out.

  Based on the XYZ values respectively corresponding to these three grid points, the estimation unit 73 has the same halftone values as the lattice point O for the four color halftone values of CMYK, and both the network of both the Or component and the G component. An XYZ value corresponding to a lattice point X having a% value of 100% is estimated. The estimation of the XYZ value is performed once from a space described by XYZ tristimulus values to an L * a * b * color space (hereinafter abbreviated as Lab space). Therefore, the estimation unit 73 converts the XYZ values respectively corresponding to the obtained three lattice points O, P, and Q into coordinate values in the Lab color space.

  FIG. 7 is a diagram schematically showing an estimation method performed by the estimation unit 73 in FIG.

FIG. 7 shows three coordinate points obtained by converting XYZ values respectively corresponding to the above three lattice points O, P, and Q into L * a * b * values (hereinafter abbreviated as Lab values). O, P, and Q are shown together with coordinates (L ₀ , a ₀ , b ₀ ), (L ₁ , a ₁ , b ₁ ), (L ₂ , a ₂ , b ₂ ). It should be noted that here, for the coordinate points in the Lab color space corresponding to the grid points in the CMYKOrG 6-color halftone space, the same signs as the grid points in the CMYKORG 6-color halftone space Is used. Further, this figure also shows an unknown coordinate point X obtained by converting the XYZ value corresponding to the lattice point X, which is the estimation target, into a Lab value, and the coordinates of the unknown coordinate point X are also shown. Is (L, a, b). The estimation unit 73 uses the coordinate point O in the Lab space corresponding to the lattice point O in which the network% values of both the Or component and the G component are 0% as a reference from the coordinate point O to the network% of the Or component. A vector OP toward the coordinate point P in the Lab space corresponding to the lattice point P having a value of 100% and a G component halftone value of 0% is obtained. Further, the estimation unit 73 moves the vector from the coordinate point O toward the coordinate point Q in the Lab space corresponding to the lattice point Q having the G component halftone value of 100% and the Or component halftone value of 0%. Find the OQ. Then, the unknown coordinate point X is estimated by weighting and adding these two vectors OP and OQ. Specifically, the vector OX from the coordinate point O toward the unknown coordinate point X is estimated by the following equation.

Here, the coefficient α relating to the whole is an adjustment parameter, and is a constant of about 1.0 to 1.5, and this value is determined empirically based on the evidence that the user receives from the output result. In the above formula, L _Or , a _Or , and b _Or are lattice points in which the halftone value of Or is 100% and the remaining halftone values of the five colors of CMYKG are all 0% (so-called Or single-color solid lattices). _Are the coordinate components of the coordinates (L _Or , a _Or , b _Or ) in the Lab space corresponding to the points). Similarly, L _G , a _G , and b _G are the remaining% of G with 100%. This is a coordinate component of coordinates (L _G , a _G , b _G ) in the Lab space corresponding to grid points (so-called G monochromatic solid grid points) in which the halftone values of the five colors of CMYKOr are 0%.

As shown in this equation, the vector OP and the vector OQ are respectively 1 / (L _Or ² + a _Or ² + b _Or ), which is the reciprocal of the chromaticity distance (color difference from the origin of the Lab space) of the Or single solid color. ² ) ^1/2 , weighted by 1 / (L _G ² + a _G ² + b _G ² ) ^1/2 which is the reciprocal of the chromaticity distance of the G monochromatic solid.

In general, when two colors are superimposed, the smaller of the lightness and saturation of the two colors has a greater influence on the color that appears when they are superimposed. In the above equation, in order to reflect such a property, the vector OP related to the grid point P having the dot% value of the Or component of 100% and the dot% value of the G component of 0% is represented by an Or single solid color. The reciprocal of the chromaticity distance 1 / (L _Or ² + a _Or ² + b _Or ² ) ^1/2 is weighted, and the grid point Q having the G component halftone value of 100% and the Or component halftone value of 0% is obtained. The vector OQ is weighted by 1 / (L _G ² + a _G ² + b _G ² ) ^1/2 which is the reciprocal of the chromaticity distance of the G single color solid, and the vector OX is estimated.

In the present invention, the weighting method is not limited to the reciprocal of the chromaticity distance, and may be a negative power other than the reciprocal, such as the (−1/3) th power of the chromaticity distance. Further, in the present invention, the contribution of lightness and the contribution of saturation do not necessarily have to be equal, as in (L _Or ² + a _Or ² + b _Or ² ) ^1/2. Generalized chromaticity distance, such as (k ₁ * L _Or ² + k ₂ * (a _Or ² + b _Or ² )) ^1/2 , multiplied by the degree contribution plus positive coefficients k ₁ and k ₂ The reciprocal of may be adopted. Or, more simply, weighting may be performed by the reciprocal of brightness only or the reciprocal of saturation only.

  When the vector OX is estimated by the above formula, the coordinate components L, a, b (see FIG. 7) of the unknown coordinate point X are obtained from this estimation. Further, by converting the Lab value into the XYZ value, the XYZ value corresponding to the lattice point where the half-tone value of both the Or component and the G component is 100% is estimated.

The estimation unit 73 in FIG. 5 performs the estimation as described above, and the mesh% values of the four colors of CMYK to be estimated are 0% or 100%, and any mesh% of the Or component and the G component. The calculation is performed for 2 ⁴ = 16 grid points whose value is also 100%, and written in the corresponding portion in the color conversion table of the composite profile.

  At the stage where all the XYZ values corresponding to these grid points are obtained, all the corresponding XYZ values are acquired for the grid points where the halftone values of the six colors of CMYKOrG are 0% or 100%. That's right.

  Returning to the flowchart of FIG.

  When the XYZ values are obtained for all the grid points where the halftone values of the six colors of CMYKOrG are 0% or 100%, the calculation unit 74 in FIG. 5 determines the remaining XYZ values based on the XYZ values of these grid points. The XYZ values at the lattice points are calculated by the difference decomposition method (step S15). Below, the specific content of this difference decomposition method is demonstrated.

  Among the edges of the six color spaces of CMYKOOrG (the line connecting the closest grid points among the grid points where the half-tone value of each color is 0% or 100%), the Or of the two grid points that are the end points Steps S12 and Step are performed for the ridgeline in which the component halftone values are both 0% and the ridgeline in which the G component halftone values of the two lattice points that are the end points are both 0%. In the process of S13, the XYZ values corresponding to the respective grid points on the edge line are already described in the color conversion table of the composite profile. The calculation unit 74 first performs calculation by the difference decomposition method for the remaining ridge lines, that is, ridge lines in which the half-value values of the Or component and the G component are 100% at at least one of the two end points. . As such ridge lines, for example, ridge lines extending in the G color direction in a color space of six colors, and for each halftone value of four colors of CMYK, a constant value of 0% or 100%, an Or component As for the mesh% value, a ridge line having a constant value of 100% can be cited. Here, the contents of calculation by the differential decomposition method will be briefly described by taking as an example the case of obtaining the X value among the XYZ values corresponding to the grid points on the ridge line.

In this embodiment, in the six-color space, the grid points are arranged such that n grid points having different G component halftone values in the G direction are arranged in total, and the G component halftone% is obtained. Order each grid in order of increasing value. At this time, the grid point of the G component of the first grid point on the ridge line is a grid point of 0% and the grid point of the G component of the nth grid point is 100%. When the X value of the k-th (k = 1,... n) lattice point is expressed as X (k), in the difference decomposition method, the corresponding X value is unknown (k = 2,... n−1) In obtaining X (k) of the lattice point, the following interpolation formula is used.
X (k) = {X (k−1) / N (k−1, k) + X (k + 1) / N (k, k + 1)}
÷ {1 / N (k−1, k) + 1 / N (k, k + 1)} (1d)
Here, N (k−1, k) and N (k, k + 1) are the lattice spacing between the (k−1) th lattice point and the kth lattice point, and the kth lattice point, respectively. This represents the lattice spacing between the (k + 1) th lattice point. This equation (1d) means that the X value of the kth lattice point can be obtained by adding the X value of the adjacent lattice points with a weight determined by the lattice interval. In the limit where these two lattice intervals are zero (so-called continuous limit), this equation (1d) is equivalent to a second-order differential equation (d / dx) ² X = 0, and is a one-dimensional Laplace equation in continuous space. Matches. Therefore, by expanding the meaning, in the following, an equation in a differential form that coincides with the Laplace equation in the continuous limit is simply expressed as the Laplace equation, as in Equation (1d) that describes the relationship between the X values of the respective lattice points. I will call it.

  Since X (1), which is the X value of the first lattice point, and X (n), which is the X value of the nth lattice point, have already been acquired, the remaining (n-2) lattices The X value of the point is an unknown number, and there are a total of (n−2) one-dimensional Laplace equations (1d) describing the relationship between these unknown numbers. Therefore, by solving this simultaneous equation, all the X values of the lattice points on this ridge line can be obtained.

  For the remaining Y and Z values, all the Y and Z values of the lattice points on this ridge line are obtained by using the Laplace equation similar to the equation (1d). The calculation unit 74 illustrated in FIG. 5 performs the above-described calculation by the differential decomposition method for all ridge lines in which the network% value of the Or and G components is 100% at at least one of the two end points. Then, the obtained XYZ value is written in the corresponding location in the color conversion table of the composite profile.

  As a result of this calculation, the XYZ values of the grid points on the ridge lines are acquired for all the ridge lines in the six color spaces.

  Next, based on the XYZ values of the lattice points on the ridge lines, the calculation unit 74 calculates the XYZ values of the lattice points on the two-dimensional surface in the square two-dimensional surface surrounded by the four ridge lines using the difference decomposition method. Calculated by Of these two-dimensional surfaces, all of the four vertices have a two-dimensional surface with an Or component halftone value of 0%, and all four vertices have a G-component halftone value of 0%. For the two-dimensional surface, the XYZ values corresponding to the lattice points on the two-dimensional surface are already described in the color conversion table of the composite profile in the process of step S12 and step S13. For this reason, the two-dimensional surface to be calculated by the differential decomposition method is the remaining two-dimensional surface, that is, at least one vertex among the four vertices of the two-dimensional surface, the network% values of the Or component and the G component are 100%. It is a two-dimensional surface. An example of such a two-dimensional surface is a two-dimensional surface surrounded by four ridge lines extending in the G color direction or the Or direction. Here, the content of calculation by the differential decomposition method will be briefly described by taking as an example the case of obtaining the X value among the XYZ values corresponding to the lattice points on the two-dimensional surface.

In the present embodiment, in the six-color space, the grid points are arranged such that a total of m grid points having different Or% dot values in the Or direction are arranged. As described above, a total of n lattice points are arranged in the G direction. Therefore, there are a total of (m × n) lattice points on the two-dimensional surface. Here, as in the case of the one-dimensional case described above, also in the Or direction, the network component of the Or component of the first lattice point is a lattice point of 0%, and the network of the Or component of the mth lattice point. Each grid is ordered in the order in which the network% value of the Or component increases so that the% value becomes a grid point of 100%. Then, the Or direction, _{k 1} th, for G direction, when the X value of the _second grid point _k is denoted as _{X (k} 1, _{k 2),} the corresponding X value is unknown _(k 1 = 2, ... For the grid points of m−1, k ₂ = 2,..., n−1), the following interpolation formula is used in the difference decomposition method.
_{X (k 1, k 2)} = [{X (k 1 -1, k 2) / M (k 1 -1, k 1) + X (k 1 + 1, k 2) / M (k 1, k 1 +1 )} ÷ {M (k ₁ −1, k ₁ ) + M (k ₁ , k ₁ +1)}
+ {X (k ₁ , k ₂ −1) / N (k ₂ −1, k ₂ ) + X (k ₁ , k ₂ +1) / N (k ₂ , k ₂ +1)} ÷ {N (k ₂ − 1, k ₂ ) + N (k ₂ , k ₂ +1)}]
_{÷ [1 / M (k 1} -1, k 1) + 1 / M (k 1, k 1 +1)
+ 1 / N (k ₂ −1, k ₂ ) + 1 / N (k ₂ , k ₂ +1)] (2d)
Here, M (k ₁ −1, k ₁ ) and M (k ₁ , k ₁ +1) in the above equation are the (k ₁ −1) th lattice point and k ₁ th lattice point in the Or direction. , And the lattice spacing between the k _1st lattice point and the (k ₁ +1) th lattice point, respectively. N (k ₂ −1, k ₂ ) and N (k ₂ , k ₂ +1) are the above-described lattice spacings in the G direction. The above equation (2d) can also be obtained by adding the X value of the lattice point to the X value of the surrounding lattice points with a weight determined by the lattice interval, similarly to the above equation (1d). I mean. The expression (2d) includes four values M (k ₁ −1, k ₁ ), M (k ₁ , k ₁ +1), N (k ₂ −1, k ₂ ), and N (k ₂ , k ₂ +1). In the limit where the lattice spacing goes to zero, it matches the two-dimensional Laplace equation in continuous space.

  Here, all the X values of the lattice points on the edge line surrounding the two-dimensional surface are acquired, and the X values of (m−2) × (n−2) lattice points are unknown. There are also (m−2) × (n−2) two-dimensional Laplace equations (2d) describing the relationship between these unknowns. Therefore, all the X values of the lattice points on the two-dimensional plane can be obtained by solving the simultaneous equations.

  For the remaining Y value and Z value, all of the Y value and Z value of the lattice point on this ridge line are acquired by using the Laplace equation similar to the equation (2d). The calculation unit 74 shown in FIG. 5 performs the calculation by the difference decomposition method for all two-dimensional surfaces in which the network% values of the Or component and the G component are 100% at at least one vertex. The obtained XYZ values are written in the corresponding locations in the color conversion table of the composite profile.

  Next, the calculation unit 74 calculates the XYZ values of the lattice points in the three-dimensional space based on the XYZ values of the lattice points on the two-dimensional surface in the three-dimensional space surrounded by the two-dimensional surfaces. Calculated by the differential decomposition method. Although details of the details of the calculation are omitted, the calculation method corresponds to extending the calculation of the XYZ values of the lattice points on the two-dimensional surface by one dimension, and the calculation of the lattice points on the two-dimensional surface. The XYZ value of the lattice point in the three-dimensional space is obtained by solving the three-dimensional Laplace equation using the XYZ value as a boundary value.

  The calculation unit 74 performs processing for solving the n-dimensional Laplace equation by using the XYZ values in the (n−1) -dimensional space, in which the XYZ values have already been obtained as the boundary value, surrounding the n-dimensional space while increasing the dimensions one by one. repeat. Finally, the XYZ values of all grid points in the CMYKOrG six-color space are calculated by solving the 6-dimensional Laplace equation using the XYZ values of the grid points in the 5-dimensional space as boundary values. At this stage, the color conversion table of the composite profile is completed.

  In general, in the output of a color image, four colors of CMYK play an important role in color expression, and Or and G play a role of assisting the color expression. For this reason, it is practically not necessary to create a highly accurate output profile for all six colors. Rather, the effort of creating an output profile by creating and measuring a color patch consisting of a combination of six colors is required. The burden is heavy.

  Therefore, in the present embodiment, as described above, for the five colors, an output profile with a certain degree of accuracy is created by creating and measuring a color patch, and these are combined to create six more colors. By adopting a method of creating an output profile, it is possible to reduce the labor required for creating the output profile while maintaining the accuracy required for practical use.

  In the embodiment described above, two types of five color output profiles are synthesized to create a six color synthesis profile. However, in the following, three types of five color output profiles are synthesized, and 7 An embodiment for creating a color composition profile will be described. This embodiment differs from the above-described embodiment in that C (cyan), M (magenta), Y (yellow), K (black), Or (orange), G (green) instead of the color printer of FIG. ), A color printer provided with B (blue) toner in addition to each color toner. Except for this point, an image output system having the same configuration as that in FIG. 1 is used to create a composite profile for seven colors of CMYKOrGB. The following description focuses on the contents of processing executed by the personal computer 20 shown in FIGS. 2 and 3 in creating a composite profile for seven colors.

  Similarly to the case of creating the composite profile for the six colors described above, the composite profile for the seven colors is also created by combining a plurality of types of output profiles for some of the seven colors. Here, as an example, a case will be described in which a composite profile for seven colors is created by combining three types of output profiles of five colors.

  First, as the original five color output profiles, the CMYKOr output profile when the G component and the B component are not used, the CMYKG output profile when the Or component and the B component are not used, the Or component, and the G component A total of three types of output profiles of five colors are created as output profiles of CMYKB when no is used. The creation method of the output profile of five colors is the same as the creation method described above, and the output of each of these CMYKOr, CMYKG, and CMYKB is output by outputting a chart having patches and measuring the color of the patches thereon. A profile is created. Hereinafter, a method of synthesizing these three types of five color output profiles to create a composite profile for seven colors will be described.

  FIG. 8 is a flowchart showing the operation of the personal computer 20 when synthesizing color conversion tables for three types of output profiles of five colors.

  First, the acquisition unit 71 shown in FIG. 5 acquires a color conversion table for the above three output profiles as a target of the synthesis process (step S21). Next, as in step S12 of FIG. 6, the setting unit 72 shown in FIG. 5 sets 0% of the halftone% of the G component, the Or component, and the B component that exist in common in these three color conversion tables. The XYZ values respectively corresponding to the grid points are read from the three color conversion tables, and the average value is written in the corresponding position in the color conversion table of the composite profile for seven colors (step S22). Next, the setting unit 72 writes the portion of the three color conversion tables that exists in only one color conversion table as it is in the corresponding portion in the color conversion table of the composite profile (step S23). .

  In the process up to step S23, the grid points of the seven color spaces of CMYKOGB whose corresponding XYZ values have not yet been obtained are grids whose half-tone values of at least two of the three colors of OrGB are not 0%. Is a point. Hereinafter, a method for obtaining XYZ values corresponding to these lattice points will be described.

The estimation unit 73 in FIG. 5 determines that the halftone values of the four colors of CMYK are 0% or 100%, the halftone values of two of the three colors of OrGB are 100%, and the remaining one color is The XYZ values corresponding to the grid points having a halftone value of 0% are estimated by the same method as in FIG. For example, the XYZ value corresponding to the lattice point where the halftone value of the two colors of OrG is 100% and the halftone value of the B color is 0% is the halftone value of the Or component as described with reference to FIG. XYZ values corresponding to grid points where the value is 100% and G and B are 0%, and the G component is 100% and G and B are 2 colors. The halftone value is estimated based on the XYZ value corresponding to the lattice point having 0%. With respect to the estimated grid points, there are 2 ⁴ = 16 ways in which the halftone value of the four colors of CMYK is 0% or 100%, and the halftone of two colors of the three colors of OrGB. Since there are three ways in which the% value is 100% and the remaining one color has a halftone value of 0%, there are 16 × 3 = 48 in total.

Further, the estimation unit 73 calculates XYZ values corresponding to lattice points where the halftone values of the four colors of CMYK are 0% or 100% and the halftone values of the three colors of OrGB are 100%. The estimation is performed by the method described below (step S24). There are 2 ⁴ = 16 such grid points because the halftone values of the four colors of CMYK are 0% or 100%. Therefore, the total number of grid points to be estimated by the estimation unit 73 is 48 + 16 = 64.

  The estimation unit 73 in FIG. 5 performs the estimation on the grid point where the halftone value of any of the three colors of OrGB is 100%, as in the method of step S14 in FIG. An XYZ value corresponding to a grid point O in which the halftone value of all colors of OrGB is 0% and the halftone value of the four colors of CMYK is the same as the halftone value of the grid point to be estimated Are read out from the XYZ values already written in the composite color conversion table. Next, the estimation unit 73 relates to the XYZ values corresponding to the grid point P in which the halftone value of the six colors of CMYKGB is the same halftone value as that of the grid point O and the half% value of the Or component is 100%. As for the six color halftone values of CMYKOrB, the same halftone value as that of the lattice point O and the halftone value of the G component corresponding to the lattice point Q where the halftone value of the G component is 100%. As for the% value, the XYZ value corresponding to the grid point R, which is the same halftone value as that of the grid point O and the B component halftone value is 100%, is read from the composite color conversion table.

  Based on the XYZ values respectively corresponding to the four grid points, the estimation unit 73 has the same halftone value as the lattice point O for the four color halftone values of CMYK, and includes the Or component, the G component, and the B component. The XYZ value corresponding to the lattice point X ′ where all halftone values are 100% is estimated. The estimation of the XYZ value is once performed from the space described by the XYZ tristimulus values to the Lab space, similarly to step S14 in FIG. Therefore, the estimation unit 73 converts the XYZ values respectively corresponding to the obtained four grid points into coordinate values in the Lab color space.

  FIG. 9 is a diagram schematically illustrating an estimation method performed by the estimation unit 73 in FIG.

In FIG. 9, three coordinate points O, P, Q, and R obtained by converting XYZ values respectively corresponding to the above three lattice points O, P, Q, and R into Lab values are represented by coordinates ( L ₀ , a ₀ , b ₀ ), (L ₁ , a ₁ , b ₁ ), (L ₂ , a ₂ , b ₂ ), (L ₃ , a ₃ , b ₃ ). Further, this figure also shows an unknown coordinate point X ′ obtained by converting the XYZ value corresponding to the lattice point X ′, which is the estimation target, into a Lab value. The coordinates of 'are (L', a ', b'). As in step S14 in FIG. 6, the estimation unit 73 sets the coordinates in the Lab space corresponding to the lattice point O where the network% values of both the Or component and the G component are 0% as the coordinate point O. The unknown coordinate point X ′ is estimated by weighting and adding the vectors OP, OQ, and OR respectively directed from the coordinate point O to the coordinate points P, Q, and R in the Lab space. Specifically, the vector OX ′ from the coordinate point O toward the unknown coordinate point X ′ is estimated by the following equation.

Here, the coefficient α ′ relating to the whole is an adjustment parameter and is a constant of about 1.5 to 2.0, and this value is determined empirically based on the proof received by the user from the output result. In the above equation, L _B , a _B , and b _B are lattice points (so-called B single color) in which the B component halftone value is 100% and the remaining five CMYKG halftone values are all 0%. This is a coordinate component of coordinates (L _B , a _B , b _B ) in the Lab space corresponding to (solid grid points). L _Or , a _Or , b _Or , and L _G , a _G , b _G are the coordinates (L _Or , a _Or , b _Or in the Lab space corresponding to the grid points of the Or single solid color, respectively, as in FIG. ), The coordinate component of the coordinates (L _G , a _G , b _G ) in the Lab space corresponding to the grid point of the G monochromatic solid.

As shown in this equation, when the three vectors OP, OQ, and OR are weighted and added, the vector OP, the vector OQ, and the vector OR are respectively chromaticity of the Or single-color solid, as in FIG. 1 / (L _Or ² + a _Or ² + b _Or ² ) ^1/2 that is the reciprocal of the distance (color difference from the origin of the Lab space), 1 / (L _G ² + a _G that is the reciprocal of the chromaticity distance of the solid G color. ² + b _G ² ) ^1/2 , weighted by 1 / (L _B ² + a _B ² + b _B ² ) ^1/2 , which is the reciprocal of the chromaticity distance of the B monochromatic solid. By weighting in this way, the above equation is devised so that colors having a large influence on the color that appears when they are superimposed and having a small lightness or saturation contribute greatly.

  When the vector OX ′ is estimated by the above formula, the coordinate components L ′, a ′, b ′ (see FIG. 9) of the unknown coordinate point X are obtained from this estimation. Further, by converting the Lab value into the XYZ value, the XYZ value corresponding to the lattice point where the half-tone values of the Or component, the G component, and the B component are 100% is estimated.

The estimation unit 73 shown in FIG. 5 performs the above-described estimation, in which the halftone values of the three colors of OrGB are 100%, and the halftone values of the four colors of CMYK are 0% or 100%. The calculation is performed for 2 ⁴ = 16 grid points, which are%, and written in the corresponding portions in the color conversion table of the composite profile.

  At the stage where all the XYZ values corresponding to these grid points are obtained, all the corresponding XYZ values are acquired for the grid points where the halftone values of the seven colors of CMYKORB are 0% or 100%. That's right.

  When the XYZ values are obtained for all grid points where the halftone values of the seven colors of CMYKOrGB are 0% or 100%, the calculation unit 74 in FIG. 5 determines the remaining XYZ values based on the XYZ values of these grid points. The XYZ values at the lattice points are calculated by the difference decomposition method described in step 15 in FIG. 6 (step S25 in FIG. 8). That is, the calculation unit 74 first obtains the XYZ values for the lattice points on the ridge lines in the seven color spaces of CMYKOrGB by solving a one-dimensional Laplace equation, and then on the two-dimensional surface surrounded by the ridge lines. Are obtained by solving a two-dimensional Laplace equation. By repeating such calculation while increasing the dimensions and finally solving the 7-dimensional Laplace equation, the XYZ values for all the lattice points are obtained. At this stage, the color conversion table of the composite profile is completed.

As described above, in the creation of a composite profile of 6 colors or 7 colors, the Laplace equation is solved on the assumption that the XYZ values of the end lattice points are the boundary conditions and all the XYZ values of the inner lattice points are unknown. However, the present invention adopts a method in which a highly reliable XYZ value is obtained in advance for some of the inner grid points by patch colorimetry and the Laplace equation is solved for the remaining inner grid points. May be. For example, taking equation (1d) as an example, there are as many unknowns as the number of grid points for which XYZ values have not been acquired, and only these unknowns appear as unknowns X (k) on the left side of equation (1d). The number of equations and the number of unknowns are the same. For this reason, even if XYZ values have been acquired for some of the inner grid points in advance, the X (k) for the some grid points can be removed by removing the equation that appears on the left side. When the XYZ values of the remaining lattice points for which no is acquired are defined as unknowns, the same number of equations as the unknowns remain. Therefore, XYZ values corresponding to all lattice points can be obtained by solving simultaneous equations composed of the remaining equations. Thus, if XYZ values are acquired in advance for some of the inner lattice points, the XYZ values become control points, which affect the Laplace equation for lattice points for which XYZ values have not yet been acquired. For this reason, the accuracy of the calculated XYZ value is improved.

  In the above example, a composite profile for seven colors is created by synthesizing three types of output profiles of five colors that are common to the four colors of CMYK. As for the original M color profile, it is sufficient that each of the N colors in the synthesized N color profile exists in the M color in any of the M color profiles. It does not depend on the number of profiles or the combination of M colors.

  The present invention can also be applied to the case of creating a profile with different color combinations, such as creating a CMYKRGB profile from a CMYKOGB profile. For example, in the case of creating a CMYKRGB profile from a CMYKOGB profile, a color conversion table is created for only five CMYKR colors by chart colorimetry, and the color conversion table and the CMYKOGB color conversion table A CMYKRGB profile can be created by combining the portion where the halftone value of the O color component is 0%. For this reason, when the color measurement of the chart is performed, the number of types of colors to be measured is small, and the effort for creating a profile is small. The same applies to the case of adding a color as in the case of creating a CMYKOGB profile by adding B color to the CMYKOG profile. In the present invention, all color components of a desired profile (for example, all colors of CMYKOGB) It is possible to create a profile without performing colorimetry on (component).

  In the above description, a color space expressed by XYZ tristimulus values is used as a device-independent color space when creating the color conversion table. In the present invention, however, the Lab color space is used. And other color spaces such as Luv color space can also be employed.

  In the above description, the estimation is performed in the Lab color space. However, this is an example, and the color space in which the estimation is performed may be another color space such as an XYZ color space or a Luv color space. It may be.

  In the present invention, not only an output profile but also an input profile may be synthesized.

1 is an overall configuration diagram of an image output system to which an embodiment of the present invention is applied. FIG. 2 is an external perspective view of the spectrocolorimeter and personal computer shown in FIG. 1. FIG. 3 is a hardware configuration diagram of the personal computer shown in FIG. 2. It is a figure which shows one Embodiment of the color conversion definition preparation program of this invention. It is a figure showing the outline of the effect | action by those elements constructed | assembled on this personal computer in order to operate the personal computer shown in FIG. 2 and FIG. 3 as one Embodiment of the color conversion definition production apparatus of this invention. . FIG. 4 is a flowchart showing an operation when a color conversion table is synthesized by the personal computer shown in FIGS. 2 and 3. It is the figure which represented typically the system of the estimation performed by the estimation part of FIG. FIG. 4 is a flowchart showing the operation of the personal computer shown in FIGS. 2 and 3 when a color conversion table for three types of output profiles of five colors is combined. It is the figure which represented typically the system of the estimation performed by the estimation part of FIG.

Explanation of symbols

20 Personal Computer 21 Main Body 21a FD Loading Port 21b CD-ROM Loading Port 22 Image Display Device 22a Display Screen 23 Keyboard 24 Mouse 25 Bus 211 CPU
212 Main memory 213 Hard disk device 214 FD drive 50 Flexible disk (FD)
215 CD-ROM drive 51 CD-ROM
216 I / O interface 30 color printer 31 image 32 chart 40 spectrocolorimeter 41 cable 60 color conversion definition creation program 61 acquisition unit 62 setting unit 63 estimation unit 64 calculation unit 71 acquisition unit 72 setting unit 73 estimation unit 74 calculation unit

Claims (4)

Represents the color obtained have use as coordinates different N colors as a color component to each other, the first color space having coordinate axes corresponding to their N-color respectively, of the first color space coordinates and a predetermined second color space A color conversion definition creation device for creating an N color conversion definition that defines a correspondence relationship with coordinates,
Coordinates of a third color space having coordinate axes corresponding to each of the M colors, representing coordinates obtained by using a part of the M colors (M <N) within the upper limit as color components. M color conversion definition that defines the correspondence between the coordinates of the second color space and the coordinates of the second color space, and a plurality of M colors in which the combination of the M colors is different and each of the N colors is included in any combination An acquisition unit configured to acquire each of a plurality of third color spaces corresponding to each combination;
A first color space defined by the N color conversion definition using a correspondence relationship between the coordinates of the third color space defined by each M color conversion definition acquired by the acquisition unit and the coordinates of the second color space. Among the coordinates of the coordinates of the second color space and the coordinates of the first color space where the color component of the color not included in the M color corresponding to the third color space is zero. A response determination unit;
An estimation unit that estimates a correspondence in a vertex whose correspondence is not yet determined in the correspondence determination unit among the vertices of the first color space based on a correspondence in a vertex whose correspondence is determined in the correspondence determination unit;
Interpolation calculation for obtaining a correspondence relationship at coordinates whose correspondence relationship is undetermined among the coordinates of the first color space based on the correspondence relationship determined by the correspondence determination unit and the correspondence relationship estimated by the estimation unit. And a color conversion definition creating device.   The interpolation calculation unit has a one-dimensional relationship between the ridge lines of the first color space having coordinates whose correspondence is undetermined, with the correspondence at the coordinates on each ridge line being the boundary condition at the end point of each ridge line. Among the two-dimensional surfaces obtained by solving the Laplace equation and surrounded by the edge of the first color space, the correspondence in the coordinates on each two-dimensional surface with respect to the two-dimensional surface having the coordinates whose correspondence is undetermined The relationship is obtained by solving the two-dimensional Laplace equation using the correspondence on the coordinates on the edge surrounding each two-dimensional surface as a boundary condition, and the correspondence obtained by solving the Laplace equation is further defined as a new boundary condition. The process of solving the Laplace equation that is raised by one is repeated while increasing the dimensions in order, and finally the N-dimensional Laplace equation is solved. And the color conversion definition creating apparatus according to claim 1, characterized in that to complete the N-color conversion definition.   The color conversion definition creating apparatus according to claim 1, wherein the second color space is a device-independent color space. Built into a computer system,
Represents the color obtained have use as coordinates different N colors as a color component to each other, the first color space having coordinate axes corresponding to their N-color respectively, of the first color space coordinates and a predetermined second color space A color conversion definition creation program for creating an N color conversion definition that defines a correspondence relationship with coordinates,
On that computer system,
Coordinates of a third color space having coordinate axes corresponding to each of the M colors, representing coordinates obtained by using a part of the M colors (M <N) within the upper limit as color components. M color conversion definition that defines the correspondence between the coordinates of the second color space and the coordinates of the second color space, and a plurality of M colors in which the combination of the M colors is different and each of the N colors is included in any combination An acquisition unit configured to acquire each of a plurality of third color spaces corresponding to each combination;
A first color space defined by the N color conversion definition using a correspondence relationship between the coordinates of the third color space defined by each M color conversion definition acquired by the acquisition unit and the coordinates of the second color space. Among the coordinates of the coordinates of the second color space and the coordinates of the first color space where the color component of the color not included in the M color corresponding to the third color space is zero. A response determination unit;
An estimation unit that estimates a correspondence in a vertex whose correspondence is not yet determined in the correspondence determination unit among the vertices of the first color space based on a correspondence in a vertex whose correspondence is determined in the correspondence determination unit;
Interpolation calculation for obtaining a correspondence relationship at coordinates whose correspondence relationship is undetermined among the coordinates of the first color space based on the correspondence relationship determined by the correspondence determination unit and the correspondence relationship estimated by the estimation unit. A color conversion definition creating program characterized by constructing a section.

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