JP2004356952A - Color controlling method, program for executing color controlling method, and recording medium storing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color controlling method capable of attaining conversion in a way such that a color printer for proofreading provides an output of an image in a single K color without mixture of dots in other colors from a region of the image outputted in single K color by a printer and attaining conversion in a way such that the color printer for proofreading provides an output of a solid image in three colors (C, M, Y) without dots from a region of the solid image outputted in the three colors by the printer. <P>SOLUTION: The K in a combination of CMYK of the color printer for proofreading for a device color link profile is obtained by using a gradation correction curve for the K, and the CMY is obtained by using a CMYK → L*a*b* LUT for the printer, which maps the L*a*b* corresponding to the combination of at least K=0 and maximum values of the CMY for the printer into the L*a*b* corresponding to the combination of K=0 and maximum values of the CMY for the color printer 2 for proofreading. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a color adjustment method, a program for executing the color adjustment method, and a recording medium storing the program, and more particularly, to image data that is output by a color image output device in a color to be output. Are converted by using a color conversion table with respect to the four basic colors (yellow (Y), magenta (M), cyan (C), and black (K)) shown in FIG. And what to adjust.
[0002]
[Prior art]
Conventionally, in a calibration color printer that outputs a halftone type color proof, since the colors of the CMYK color materials are close to the printing ink colors, correction of the difference in halftone dots (dot gain curve correction) is performed for each color of CMYK. By performing the measurement based on the measurement result of the dot area ratio, it was possible to match the color to the printing press to some extent. However, secondary colors of red R, green G, and blue B, black by three CMY colors, black by four CMYK colors, and colors in the vicinity thereof are different from the printing press in color appearance, and it is difficult to perform exact color matching. there were. Therefore, for example, a so-called color management system has been proposed, and color adjustment such as matching the color of the color printer for calibration with the color of the printing press has become possible.
[0003]
Here, as an example, the color management system includes a look-up table (CMYK → L) of color characteristic values such as L * a * b * values for a combination of a plurality of basic color parameters in a proof color printer or printing press. * A * b * LUT) and a device color profile representing an output color characteristic of an output device of a lookup table (L * a * b * → CMYK LUT) of a combination of a plurality of basic color parameters with respect to a plurality of color characteristic values. (C is cyan (blue-green), M is magenta (magenta), Y is yellow (yellow), K is black (black), and L * a * b * values are three-dimensional spaces representing colors. Where h * / saturation is represented by the a * b * plane, L * is orthogonal to the a * b * plane, and represents lightness, and LUT is a look-up table. Device link color profile CMYK that converts a combination of CMYK parameters so that a target color output by a printing press is output by a calibration color printer. There is a printer that creates a CMYK LUT and matches the color of the color printer for calibration with the color of the printing press using the CMYK → CMYK LUT.
[0004]
However, in the color adjustment method based on the above-described conversion, CMYK is converted into a color system value in the device color profile of the printing press, and the color system value is converted into CMYK in the device color profile of the calibration color printer. Therefore, although the K single color part is replaced with CMYK four colors and K is output as a single color in the output of the printing press, other colors may be mixed in the color proof output by the proof color printer, and the character quality is degraded. In some cases, the solid portion of the three colors CMY was not reproduced as a solid portion, and a halftone dot was included. In particular, for color proofs output by a proof color printer that reproduces the halftone images output by the printing press, the proofreader may use a loupe to check the appearance of the halftone dots. , Or halftone dots mixed in the solid portions of the three colors may cause errors in calibration. In addition, the appearance of a moiré pattern or a rosette pattern may change due to a change in the amount of the K plate, or a K color printer may be used for a calibration color printer other than a halftone type such as an ink jet printer or an electrophotographic printer. The character quality was degraded due to the CMYK four colors being replaced.
[0005]
In view of this, there is a printer in which the K single-color portion is output in the same manner in a color printer for calibration while performing color adjustment by the above-described conversion (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-2000-330302 (paragraphs [0015] to [0140], FIGS. 1 to 27)
[0007]
[Problems to be solved by the invention]
However, in the above-described calibration color printer, the K single color is reproduced as a K single color, but the solid colors of CMY are not taken into consideration, so that they are not reproduced as solid as described above, and halftone dots are included. When the proofreader uses a loupe to check, the appearance of the halftone dots is different, which is not preferable.
[0008]
The present invention has been made in view of the above circumstances, and a purpose thereof is to target a color of an image based on image data output from a printing press and to output the image with a color printer for proofreading. When the combination of the parameters of the four basic colors (C, M, Y, K) of the image data is converted using the color profile (CMYK → CMYK LUT) so as to output the target color, printing is performed. For the area output in K single color by the printing machine, the color printer for calibration also converts so as to output as a K single color without mixing the halftone dots of other colors, and also prints three colors (C, M, Y). A color adjustment method capable of converting a solid color output area so as to output three-color solids without halftone dots even in a proof color printer. It is to provide a recording medium which stores a program and a program for.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a color of an image output based on image data in a first color image output device is set as a target of color matching, and the target color is set as a second color. In order to reproduce with the color image output device, the combination of the parameters of the four basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) on the input side is applied to the four colors on the output side. A color conversion table that associates four basic color parameter combinations for outputting the color output by the first color image output device with the second color image output device by the combination of the basic color parameter A color adjustment method for adjusting a color by converting parameters of four basic colors shown in the image data using the first color image output device and the second color image output device. A first lookup table in which color characteristic values indicating colors output by each combination are associated with combinations of parameters of the respective four basic colors; and a first lookup table for the second color image output device. Creating a second reference table that associates a combination of four basic color parameters for outputting a color indicated by each color characteristic value with a plurality of color characteristic values based on the reference table; The output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the first and second color image output devices. Creating a correction characteristic for correcting a parameter of K; a first lookup table of the first color image output device; and a second lookup table of the second color image output device. Is used to create the color conversion table, and at the time of the creation, at least the combination of the parameter of K in the first reference table of the first color image output device is 0 and the parameter of the three CMY colors is the maximum value. Is mapped to a color characteristic value corresponding to the combination of the three CMY parameters with the K parameter being 0 in the first lookup table of the second color image output device. The combination of the three CMY color parameters with the K parameter set to 0 among the four basic color parameters on the input side of the created color conversion table is obtained from the combination of the four basic color colors on the output side. , K when the parameter is set to 0, the combination of the three CMY color parameters is referred to as the first reference table of the second color image output apparatus. Table, and replaces the combination of the four basic color parameters on the output side of the created color conversion table with the determined combination of the three CMY parameters and the K parameter corrected using the correction characteristics. Re-creating the color conversion table.
[0010]
Further, the invention according to claim 2 is characterized in that the obtained combination of three CMY parameters is obtained from the combination of the four basic colors on the output side with respect to the combination of three CMY parameters with the K parameter being 0. A color characteristic value is determined using the first reference table of the second color image output device, and the color characteristic value is determined from the color characteristic value using a case where the parameter of K in the first reference table is 0. It is characterized by.
[0011]
According to a third aspect of the present invention, a color of an image output based on image data in a first color image output device is set as a color matching target, and the target color is reproduced in a second color image output device. In order to achieve this, the combination of the parameters of the four basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) on the input side are combined with the parameters of the four basic colors on the output side. The color data output from the first color image output device in combination with the image data using a color conversion table in which a combination of parameters of four basic colors for output by the second color image output device are associated. A color adjustment method for adjusting the color by converting the parameters of the four basic colors shown, wherein each of the first color image output device and the second color image output device has four basic colors. A first reference table in which a color characteristic value indicating a color output by each combination is associated with a combination of parameters, and a plurality of color characteristics based on the first reference table for the second color image output device. Creating a second reference table in which a combination of parameters of four basic colors for outputting a color indicated by the value of each color characteristic is associated with the first color image and the first and second color images. A correction for correcting a parameter of K so that an output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the output device. Creating a characteristic; and using the first look-up table of the first color image output device and the second look-up table of the second color image output device. At the time of creating the table, at the time of the creation, at least the color characteristic values corresponding to the combination of the maximum values of the three CMY parameters in the first reference table of the first color image output device are set to the K parameter. Mapping the combination of the three CMY colors as the maximum value as the value corrected by the correction characteristic to the value of the color characteristic obtained from the first reference table of the second color image output device; For the combination of the four basic color parameters on the input side of the color conversion table, the parameter of K is corrected using the correction characteristic, and the four basic colors of the input side in the created color conversion table are corrected. The second color image is obtained from the combination of the parameters of the four basic colors on the output side corresponding to the combination of the parameters. Using the first reference table of the output device, a combination of three CMY parameters with the corrected K parameter is obtained, and the four basic color parameters on the output side of the created color conversion table are obtained. And re-creating the color conversion table by replacing the combination of CMY parameters with the determined combination of three CMY parameters and the corrected K parameter.
[0012]
According to a fourth aspect of the present invention, a color of an image to be output based on image data in a first color image output device is set as a color matching target, and the target color is reproduced in a second color image output device. In order to achieve this, the combination of the parameters of the four basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) on the input side are combined with the parameters of the four basic colors on the output side. The color data output from the first color image output device in combination with the image data using a color conversion table in which a combination of parameters of four basic colors for output by the second color image output device are associated. A color adjustment method for adjusting the color by converting the parameters of the four basic colors shown, wherein each of the first color image output device and the second color image output device has four basic colors. A first reference table in which a color characteristic value indicating a color output by each combination is associated with a combination of parameters, and a plurality of color characteristics based on the first reference table for the second color image output device. Creating a second reference table in which a combination of parameters of four basic colors for outputting a color indicated by the value of each color characteristic is associated with the first color image and the first and second color images. A correction for correcting a parameter of K so that an output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the output device. Creating a characteristic; and using the first look-up table of the first color image output device and the second look-up table of the second color image output device. At the time of creating the table, at the time of the creation, at least the color characteristic values corresponding to the combination of the maximum values of the three CMY parameters in the first reference table of the first color image output device are set to the K parameter. Mapping the combination of the three CMY colors as the maximum value as the value corrected by the correction characteristic to the value of the color characteristic obtained from the first reference table of the second color image output device; A combination of parameters of the four basic colors on the output side of the color conversion table is converted by the first reference table of the second color image output device to obtain a value of the color characteristic, and the obtained value of the color characteristic is obtained. Calculating a saturation from a combination of parameters of at least the four basic colors on the output side where the calculated saturation is equal to or less than a predetermined saturation. For the combination of the parameters of the four basic colors on the input side of the created color conversion table, the K parameter is corrected using the correction characteristics, and the input side of the created color conversion table in the color conversion table is corrected. K obtained by performing the correction using the first reference table of the second color image output apparatus from the combination of the four basic color parameters on the output side corresponding to the combination of the four basic color parameters. , And the combination of the four basic colors on the output side of the created color conversion table is combined with the determined combination of the three CMY parameters and the corrected K. Re-creating the color conversion table by replacing the parameters with parameters.
[0013]
The invention according to claim 5, wherein the determined combination of the three CMY parameters is obtained by combining the parameters of the four basic colors on the output side with the first reference table of the second color image output device. Is used to determine the value of the color characteristic, and from this value of the color characteristic, the parameter of K in the first reference table is determined using the corrected parameter.
[0014]
The invention according to claim 6 further comprises an output corresponding to a combination in which the parameters of the four basic colors on the input side of the recreated color conversion table are C = M = Y = 0 and K is not 0. The C, M, and Y parameters of the combination of the four basic color parameters on the input side are changed to C = M = Y = K = 0 on the input side of the recreated color conversion table. Are replaced with C, M, and Y parameters of the combination of the parameters of the four basic colors on the output side corresponding to the combination of.
[0015]
According to a seventh aspect of the present invention, there is further provided the output four colors corresponding to a combination of the maximum values of C, M, and Y of the four basic colors on the input side of the recreated color conversion table. Are characterized in that the C, M, and Y parameters of the combination of the basic color parameters are set to the maximum values.
[0016]
Further, in the invention according to claim 8, the correction characteristic is obtained by using the first reference table of each of the first color image output device and the second color image output device. It is characterized in that the brightness obtained from the color characteristic value for the maximum value of the K parameter in the first lookup table of the output device to 0 is reproduced so as to be reproduced by the second color image output device. .
[0017]
According to a ninth aspect of the present invention, the correction characteristic is such that when a parameter of K of the first color image output device is a maximum value, a parameter of K of the second color image output device is set to a maximum value. It is characterized in that it is created as follows.
[0018]
According to a tenth aspect of the present invention, there is provided a program for causing a computer to execute the color adjustment method according to any one of the first to ninth aspects.
[0019]
According to an eleventh aspect of the present invention, there is provided a recording medium in which the program according to the tenth aspect is recorded so as to be readable by the computer.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
According to the present invention, for example, a color of an image based on image data output from a printing machine (first color image output device) is targeted, and the image is output by a color printer for calibration (second color image output device). Sometimes, the combination of the parameters of the four basic colors (C, M, Y, K) of the image data so that the target color is output, and the combination of the parameters of the four basic colors on the input side are: A device link color in which the combination of the four basic color parameters is associated with the output side so that the color when the combination of the four basic color parameters on the input side is printed by the printing press is output by the color printer for calibration. When converting using a profile (CMYK → CMYK LUT (color conversion table)), the area output in K single color on the printing machine is output to the proof color printer. However, the conversion is performed so that halftone dots of other colors are output without being mixed as a single K color, and the three-color (C, M, Y) solid output area of the printing machine is also used by a proof color printer. The conversion is performed so as to output three-color solids without halftone dots. For this purpose, the K on the output side of the device link color profile is determined based on the device color profile of the printing press (CMYK → L * a * b * LUT) and the device color profile of the proof color printer (CMYK → L * a * b *). LUT) and a gradation correction curve for K based on the CMY are obtained by converting the gradation correction curve. CMY is used for at least three colors (C, M) of the device color profile of the printing press (CMYK → L * a * b * LUT). , Y) are mapped to the L * a * b * values of the output values of the device color profile (CMYK → L * a * b * LUT) of the corresponding color printer for calibration. Then, it is determined using the device color profile (CMYK → L * a * b * LUT) of the printing machine on which the mapping has been made (details will be described later). .
[0021]
Here, the four basic colors (C, M, Y, K) are as follows: C is cyan (cyan), M is magenta (purplish red), Y is yellow (yellow), and K is black (black). is there. The parameters are so-called gradations, halftone dot area ratios, and the like. In the following embodiments, gradations are represented by numerical values such that the minimum value is 0 and the maximum value is 255. 0 is white, and 255 represents, for example, a dot area ratio of 100%, i.e., solid, and, for example, "CMYK combination", "K" or the like below indicates "CMYK The "combination of parameters" and "K parameter" indicate the value of the gradation. The L * a * b * value is a value of a color system and represents a color in a three-dimensional space of an L * axis, a * axis, and b * axis. Degree is represented, and L * is a value of a color characteristic which is orthogonal to the a * b * plane and represents lightness. LUT is a lookup table (reference table).
[0022]
Hereinafter, an embodiment of an image forming system according to the present invention will be specifically described with reference to the drawings.
[0023]
(Control configuration)
First, a control configuration according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a functional block diagram of a control device 1 for performing color adjustment according to the present invention.
[0024]
The control device 1 is a so-called computer, which functions as a controller that controls image forming control of the proof color printer 2, and as shown in FIG. 1, an HDD that stores programs, image data, various lookup tables, and the like. (Hard Disk Drive), a CMYK gradation of the image data is converted by converting the CMYK gradation of the image data so that the proof color printer 2 outputs an image with a color output from a target printing machine (not shown). The control unit 11 has a function of performing adjustment and controlling the calibration color printer 2 so as to form an image. Although not shown, an input means for inputting image data and measurement results of color patches is provided. Further, a display such as a CRT, a mouse, a keyboard and the like may be provided.
[0025]
The storage unit 10 includes an image data storage unit 12 that stores image data transmitted from a work terminal (not shown), a measurement table 131 that stores color patch measurement results, an LUT storage unit 13 that stores various lookup tables, and a control device. 1, a program for creating various look-up tables from measurement results of color patches, a program for converting CMYK gradations of image data to perform color adjustment, an image forming apparatus A program for controlling the image formation in step 2 is stored in a specific directory.
[0026]
Also, a program for creating various look-up tables from color patch measurement results and a program for converting CMYK gradations of image data to perform color adjustment are provided on a floppy (registered trademark) disk, a CD-ROM, for example. Or a portable recording medium such as a magnetic recording tape. When the program software is executed by a computer, the program software can be read from the recording medium by a reading device attached to the computer.
[0027]
The control unit 11 has a function of controlling the entire control device 1 based on a program, such as a CPU, stored in the storage unit 11 and a function of controlling image forming control of the proof color printer 2. Also, an LUT creation unit 15 that creates various lookup tables based on a program stored in the storage unit 11, and a device link color profile (CMYK → CMYK) created by the LUT creation unit 15 and stored in the LUT storage unit 13. LUT), the CMYK gradation of the image data is converted based on a program stored in the storage unit 11 so that the proof color printer 2 outputs an image with a target color output from the printing press. A color adjusting unit 14 for performing adjustment is provided. The details of a method of creating various look-up tables and a color adjustment method using the CMYK → CMYK LUT 137 will be described later.
[0028]
In addition, various lookup tables stored in the LUT storage unit 13 include a CMYK → L * a * b * LUT 132 (first reference table) of a printing machine constituting a device color profile of the printing machine, and a printing machine. L * a * b * → CMYK LUT 133, CMYK → L * a * b * LUT 135 (first reference table) of calibration color printer 2 that constitutes the device color profile of the calibration color printer, calibration color printer 2 L * a * b * → CMYK LUT 136 (second reference table), and the CMYK floor of the image data so that the proof color printer 2 outputs an image with the target output color of the printing press. There is a CMYK → CMYK LUT 137 as a device link color profile for converting a key. In addition, there is a K gradation correction curve 134 (correction characteristic) used in a process of obtaining a CMYK → CMYK LUT 137 as a device link color profile.
[0029]
(Color adjustment method)
Next, a color adjustment method performed by the control device 1 of the present embodiment will be described. FIG. 2 is a flowchart showing each step of the color adjustment method according to the present embodiment. First, each step of the color adjustment method will be schematically described with reference to FIG.
[0030]
First, the LUT creation unit 15 receives the printout output from the printing press and the colorimetric results of the color chart of the calibration color printer, and creates a device color profile based on the measurement results (step S101 in FIG. 2; Omitted, and other steps are similarly omitted).
[0031]
Next, a device link color profile composed of a combination of CMYK in the printing press as a combination of CMYK on the input side and a combination of CMYK of the proof color printer 2 is created as a combination of CMYK on the output side (S102).
[0032]
In the present embodiment, the combination of CMYK of the calibration color printer 2 of the device link color profile is used, and for K, the gradation correction of K is performed based on the device color profile of the printing press and the device color profile of the calibration color printer 2. A curve 134 is created and converted using the K gradation correction curve 134 to obtain CMY. At least K = 0 in the device color profile of the printing press and C * corresponds to the maximum value of CMY. CMYK → L * a * b * of the printing machine in which the * b * value is mapped to the L * a * b * value corresponding to the combination of the maximum value of CMY with K = 0 in the device color profile of the color printer 2 for calibration. Create a device link color profile using the LUT 132 (described later in detail)
[0033]
Next, the color adjustment unit 14 performs color adjustment by converting the CMYK gradations of the image data one pixel at a time using the device link color profile (S103). Then, the converted image data is transmitted to the proof color printer 2, and the proof color printer 2 outputs an image based on the transmitted image data.
[0034]
First, the contents and creation method of the above-described device color profile will be described in detail.
[0035]
(S101)
As described above, the device color profile of each of the printing press and the proofreading color printer 2 is composed of the following two look-up tables. In the following description, the CMYK → L * a * b * LUT is replaced with the printing press described above. Of the CMYK → L * a * b * LUT 132 and the CMYK → L * a * b * LUT 135 of the color printer 2 for proofreading, and the L * a * b * → CMYK LUT is printed as described above. This is used to explain the method of creating the L * a * b * → CMYK LUT 133 of the printer and the L * a * b * → CMYK LUT 136 of the color printer 2 for calibration.
[0036]
Here, the CMYK → L * a * b * LUT converts a combination of CMYK into a value L * a * b * of a color system, and converts the colors output by each combination into four basic color combinations. L * a * b * values are associated with each other, and the L * a * b * → CMYK LUT converts a color system value L * a * b * into a combination of CMYKs. The b * value is associated with a combination of parameters of four basic colors for outputting the color indicated by each L * a * b * value. Also, since the L * a * b * → CMYK LUT has a limited color reproducible range of CMYK mixed colors by the device in the full color coordinate space of L * a * b *, how is it within the color reproducible range? It is common to change the mapping method in several ways to map the full color coordinate space of L * a * b *, to have a plurality of them, and to select and use them according to the type of input device.
[0037]
The CMYK → L * a * b * LUT is, for example, as shown in FIG. 3, and is a four-dimensional input / three-dimensional output in which an L * a * b * value is input to a CMYK LUT input point. Color patches for a large number of combinations covering the entire CMYK color space are measured with a colorimeter, and the L * a * b * values of each color patch are calculated and LUTs are obtained. it can.
[0038]
That is, the minimum value 0 to the maximum value 255 of each of C, M, Y, and K is divided into four, and five stages of 0, 64, 128, 191, and 255 are taken, and C × M × Y × K: 5 × 5 A color chart as shown in FIG. 4 in which color patches for a combination of × 5 × 5 = 625 points are arranged is printed by a printing machine or a color printer 2 for calibration, and each patch of 5 × 5 × 5 × 5 = 625 points is printed. L * a * b * values are obtained by measuring in order.
[0039]
Further, the central four-dimensional input / three-dimensional output LUT indicates that 5 × 5 × 5 × 5 = 625 points of each patch between 9 × 9 × 9 × 9 grid points are 9 × 9 × 9 × 9 by performing interpolation on each patch. As shown in FIG. 5, when a black circle is a grid point (sample point), and a mark and a mark are points to be interpolated, respectively, there are two grid points before and after the mark as shown by a mark; Different interpolation formulas are used when there are one and three points before and after as indicated by the marks.
[0040]
Here, when the color system of the point to be interpolated is Lm *, am *, bm *, and the color system of each sample point is Li *, ai *, bi * (i = 1 to 4), In the case of (△), the following interpolation formula is used.
Lm * =-(1/16) L1 * + (9/16) L2 * + (9/16) L3 *-(1/16) L4 *
am * =-(1/16) a1 * + (9/16) a2 * + (9/16) a3 *-(1/16) a4 *
bm * =-(1/16) b1 * + (9/16) b2 * + (9/16) b3 *-(1/16) b4 *
Is interpolated.
[0041]
In the latter case (marked by x), for example, for the point between i = 1 and i = 2,
Lm * = (5/16) L1 * + (15/16) L2 *-(5/16) L3 * + (1/16) L4 *
am * = (5/16) a1 * + (15/16) a2 *-(5/16) a3 * + (1/16) a4 *
bm * = (5/16) b1 * + (15/16) b2 *-(5/16) b3 * + (1/16) b4 *
Is interpolated.
[0042]
FIG. 6 shows an example of the order of interpolation processing for CMY three dimensions. The CMY 5 × 5 × 5 is interpolated into 9 × 9 × 9 by performing the interpolation processing in the order of numbers (1), (2), and (3) shown in FIG. 6 (corresponding to the Roman numerals in FIG. 6). Furthermore, after performing interpolation of CMY5 × 5 × 5 to 9 × 9 × 9 for all five K levels, for each point of CMY9 × 9 × 9, calculation is performed to interpolate the five points of K to nine points. Is performed in the same manner as in the method shown in FIG. By this, although actually measuring only patches of 5 × 5 × 5 × 5 = 625 points, the L * a * b * values of the CMYK combinations are expanded to 9 × 9 × 9 × 9 = 6561 points. You can ask.
[0043]
On the other hand, the L * a * b * → CMYK LUT is a three-dimensional input / 4-dimensional output LUT as shown in FIG. 7, and a point between 33 × 33 × 33 grid points is converted by performing interpolation. . FIG. 8 shows a procedure for creating the L * a * b * → CMYK LUT.
[0044]
As shown in FIG. 8, the method for obtaining the three-dimensional input / four-dimensional output LUT includes the following steps S01 to S04. For simplicity, the basic colors will be described as two colors C and M. Note that C, M, Y, and K all take values from 0 to 255.
[0045]
(S01)
C × M × Y × K of the CMYK → L * a * b * LUT: C × M × Y: 9 from the four-dimensional data which is the L * a * b * value for 9 × 9 × 9 × 9 Conversion to three-dimensional data, which is an L * a * b * value for × 9 × 9, is performed. For this purpose, the method described in the specification of Japanese Patent No. 2898030 by the present applicant can be used. For example, K is added based on the minimum value of CMY so that K is added to emphasize the gray component obtained from the minimum value of CMY, and L * a * b * for the case where K is added to CMY. This is done by finding the value.
[0046]
K can be obtained by the following equation. Assuming that the minimum value of CMY is min [C, M, Y],
K = 1.6 (min [C, M, Y] -128)
However, when the right side is 0 or negative, K = 0.
[0047]
The L * a * b * value when this K is added to CMY can be obtained, for example, as follows. Taking the case of C = M = Y = 191 as an example,
K = 1.6 × (191-128) = 101,
This 101 is the fourth 96 and 5 of 9 points (0, 32, 64, 96, 128, 159, 191, 223, 255) of 9 × 9 × 9 × 9 K of C × M × Y × K. L * a * of points C = M = Y = 191 (7th point) and K = 96 (4th point) among 9 × 9 × 9 × 9 points It is interpolated and calculated from two values of the b * value and the point L * a * b * values of C = M = Y = 191 (7th point) and K = 128 (5th point). The weight w1 for L1 * a1 * b1 * which is the L * a * b * value of C = M = Y = 191 (7th point) and K = 96 (4th point) is expressed as w1 = 1.0- ( 101−96) / (128−96), C = M = Y = 191 (7th point), L = a * b * value of K = 128 (5th point), weight for L2 * a2 * b2 * Assuming that w2 is w2 = (101-96) / (128-96), the L * a * b * value and Lm * am * bm * after interpolation are
Lm * = w1 × L1 * + w2 × L2 *
am * = w1 × a1 * + w2 × a2 *
bm * = w1 × b1 * + w2 × b2 *
Can be determined by:
[0048]
This is the case where C = M = Y = 191. By performing this for C × M × Y: 9 × 9 × 9 = 729 points, C × M × Y × K: 9 × 9 × 9. C × M × Y: 9 × 9 × 9 three-dimensional data can be created from × 9 four-dimensional data.
[0049]
(S02)
Next, L * a * b * → CMYK LUT is calculated using the three-dimensional data of C × M × Y: 9 × 9 × 9 in step S01. FIG. 9 is a plot of L * on the vertical axis and a * on the horizontal axis for a two-dimensional 9 × 9 combination of M and C (Y = 0) in CMY. Although it is actually three-dimensional, it is shown in two dimensions for simplicity.
[0050]
For this CMY distribution, target point [L * (0-100) a * (-127-128) b * (-127-128): 33 × 33 × 33 = 35937 LUT inputs to be obtained L * a * b * of the point is given as the target value T ′. When the target value T ′ is within the area surrounded by the lattice points a ′ to d ′ as shown in FIG. 9, the combination of MCs (the target value T) in the MC coordinate system is as shown in FIG. It is presumed that it is in the area surrounded by d. Then, where the target value T is located in the area formed by the lattice points a to d is obtained by performing convergence calculation processing while associating the color system of FIG. 9 with the coordinate system of FIG. The convergence calculation process is performed in such a way that the conversion from the coordinate system of FIG. 10 to the color system of FIG. 9 is known, but the reverse conversion is very complicated and a good conversion formula is known. This is because it has not been done.
[0051]
Next, a region SP formed by lattice points a to d in FIG.₀To four areas SP₁~ SP₄Divide equally. The five division points e to i are calculated by weighted averaging using surrounding grid points that have already been obtained. Then, values obtained by converting the values corresponding to the division points e to i into the L * a * b * color system are plotted in the color system of FIG. 12, and the plotted division points e ′ to i ′ are used. Four areas SP formed₁’-SP₄In which region the target value T 'is located. As shown in FIG.₂′, The target value T is in the region SP as shown in FIG.₂’Area SP₂It is estimated that there is.
[0052]
Next, the estimated area SP₂To four areas SP₅~ SP₈Divide equally. The five division points j to n are calculated by weighted averaging using surrounding grid points or division points that have already been obtained. Then, values obtained by converting the values corresponding to the division points j to n into the L * a * b * color system are plotted in the color system of FIG. 12, and the plotted division points j ′ to n ′ are used. Four areas SP formed₅’-SP₈In which region the target value T 'is located. As shown in FIG.₈′, The target value T is in the region SP as shown in FIG.₈’Area SP₈It is estimated that there is.
[0053]
Next, the estimated area SP₈To four areas SP₉~ SP₁₂Divide equally. The five division points o to s are calculated by weighted averaging using surrounding grid points or division points that have already been obtained. Then, values obtained by converting the values corresponding to the division points o to s into the L * a * b * color system are plotted in the color system of FIG. 12, and the plotted division points o ′ to s ′ are used. Four areas SP formed₉’-SP₁₂In which region the target value T 'is located. As shown in FIG.₁₀′, The target value T is in the region SP as shown in FIG.₁₀’Area SP₁₀It is estimated that there is.
[0054]
By repeating the above-described region division, the grid gradually becomes smaller and finally converges. Then, the target value T is obtained by averaging the four grid points or division points that form the converged region. Therefore, it is possible to obtain a combination of basic colors indicating the output colors to be obtained.
[0055]
Further, in the present embodiment, the method using the convergence operation as described above is described, but an interpolation method as described in the specification of Japanese Patent No. 2895086 by the present applicant may be used.
[0056]
Incidentally, when the target value T ′ is outside the color reproduction range formed by the vertices W ′, C ′, M ′, and B ′ of the L * a * b * color system as shown in FIG. It is necessary to move the target value T 'within the color reproduction range. In this case, the target value T 'is moved in the achromatic color direction, and the coordinates of the intersection between the straight line in the achromatic color direction and the boundary of the color reproduction range are set as the target value T' as shown in FIG. A target value T corresponding to the target value T 'is calculated.
[0057]
Note that the target value T 'does not necessarily need to be moved to the boundary, but may be moved within the color reproduction range. Although an example of a C × M two-dimension is shown here for the sake of explanation, it is actually performed on a C × M × Y three-dimension, and 33 × 33 × 33 points of L * a * b * are used. It is necessary to calculate the values of C, M, and Y one by one with each LUT input point as the target value T '.
[0058]
(S03)
C, M, and Y for 33 * 33 * 33 points of L * a * b * obtained in S02 are CMY corresponding to three-dimensional data of C * M * Y: 9 * 9 * 9 obtained in S01. And K is obtained from CMY in the same manner as in the first step.
K = 1.6 (min [C, M, Y] -128)
However, when the right side is 0 or negative, K = 0.
[0059]
(S04)
The CMYK values for the 33 * 33 * 33 LUT input points of L * a * b * obtained as described above are converted into LUTs.
[0060]
As described above, the CMYK → L * a * b * LUT and L * a * b * → CMYK LUT are created for the printing press and the proof color printer 2, respectively, and the CMYK → L * a * b of the printing press. * LUT 132, L * a * b * of printing press → CMYK LUT 133, CMYK of color printer 2 for calibration → L * a * b * LUT 135, and L * a * b * → CMYK LUT136 of color printer 2 for calibration It is stored in the LUT storage unit.
[0061]
(S102)
Next, the contents of the above-described device link color profile and a method for creating the profile will be described.
[0062]
The device link color profile is, for example, a four-dimensional input / four-dimensional output LUT in which CMYK values are input for LUT input points of C × M × Y × K: 21 × 21 × 21 × 21 = 194481 as shown in FIG. Yes, it is created using the device color profile of the printing press and the proofreading color printer 2, for example, according to the procedure shown in the flowchart of FIG.
[0063]
(S31)
First, an L * value is obtained for the K single color (0, 32, 64, 96, 128, 159, 191, 223, 255) from the CMYK → L * a * b * LUT 132 of the printing press. The L * values are assumed to be Lin1, Lin2, Lin3, Lin4, Lin5, Lin6, Lin7, Lin8, and Lin9.
[0064]
Next, from the CMYK → L * a * b * LUT 135 of the calibration color printer which is the second color image output device, L for K single colors (0, 32, 64, 96, 128, 159, 191, 223, 255) * Find the value. The L * values are defined as Lout1, Lout2, Lout3, Lout4, Lout5, Lout6, Lout7, Lout8, Lout9.
[0065]
As shown in FIG. 18, from the above-mentioned Lin1 to Lin9 and Lout1 to Lout9, the brightness data L * obtained from the value of the color system is reproduced from the maximum density point of K single color of the printing press to 0. Next, a K gradation correction curve 134 as shown in FIG. 19 is created by calculating the K value of the calibration color printer.
[0066]
In the K gradation correction curve 134, white L * may be different between the printing press and the calibration color printer in practice, so that the white (0) is not corrected to match L *. Curve. If the minimum brightness of K of the printing press is smaller than the minimum brightness of K of the proof color printer, the brightness L * cannot be reproduced. I do. Further, in this embodiment, the output value of the input value 255 of the K gradation correction curve 134 is set to 255. As a result, the solid image of K is output solid, and the character reproduction can be improved.
[0067]
(S32)
Here, the CMYK of the printing press → L * a * b * L * a * b * value for the combination of CMY when K = 0 in the LUT 132, and L * a * b * value for the combination of at least CMY of the maximum value Is mapped as shown in FIG. 20 so that K = 0 of the CMYK → L * a * b * LUT 135 of the color printer for calibration 2 and CMY match the L * a * b * value for the maximum value combination.
[0068]
FIG. 20 is a cross-sectional view of a low lightness portion near the CMY maximum value of the CMY color space of K = 0 of the printing press and low lightness close to the CMY maximum value of the CMY color space of K = 0 of the calibration color printer 2. In the sectional view of the portion, L * is shown on the vertical axis and a * is shown on the horizontal axis. Although shown in two dimensions for simplicity, it is actually three dimensional, and mapping is performed for b * as follows.
[0069]
The mapping of the L * a * b * values for the combinations of the maximum values of CMY is such that the CMY of the printing press sets the maximum L * a * b * value (L0, a0, b0) to the maximum value of CMY of the color printer 2 for calibration. The value is mapped to the L * a * b * value (L1, a1, b1). However, in this embodiment, the L value is smaller than the Lfix shown in FIG. 20, for example, so that the L * a * b * value after the mapping maintains continuity. For example, the L * a * b * value before the mapping is set to (L, a, b) and the L * a * b * value after the mapping is set to (f (L), f (a), f (b)),
f (L) = L − {(Lfix−L) / (Lfix−L0)} × (L0−L1), f (a) = a − {(Lfix−L) / (Lfix−L0)} × (a0 −a1), f (b) = b − {(Lfix−L) / (Lfix−L0)} × (b0−b1), where L ≦ Lfix,
Map according to
[0070]
(S33)
Next, using the CMYK → L * a * b * LUT 132 of the printing press that performed the mapping of the L * a * b * values in S32 and the L * a * b * → CMYK LUT 136 of the color printer 2 for calibration, C × M × Y × K: 21 × 21 × 21 × 21 = 194481 points of a combination of 21 points obtained by equally dividing 0 to 255 into 20 as shown in FIG. For example, a four-dimensional input / four-dimensional output CMYK → CMYK LUT (1) in which the CMYK values to be output to the calibration color printer 2 for each point are entered as output values is calculated.
[0071]
C × M × Y × K: 21 × 21 × 21 × 21 = 194481 Each input point is calculated by the procedure shown in FIG.
[0072]
(S11)
First, L * a * b * is obtained by using the CMYK → L * a * b * LUT 132 of the printing machine on which the L * a * b * values have been mapped in S32. C = 25.5 (2 at 0-20), M = 51 (4 at 0-20), Y = 191.25 (15 at 0-20), K = 76.5 (6 at 0-20) Taking a point as an example, the distance between an input point in CMYK: 9 × 9 × 9 × 9 of the L * a * b * LUT and each input point of CMYK is
C: Since 25.5 / 255 × 8 = 0.8, the distance DC1 between the first points C1 and C1 of C and the distance DC2 between the second points C2 and C2 of C are C1 = 0. , DC1 = 0.8, C2 = 1, DC2 = 0.2
Since M: 51/255 × 8 = 1.6, the distance DM1 between the first point M1 of M and M1 and the distance DM2 between the second points M2 and M2 of M are M1 = 1, DM1 = 0.6, M2 = 2, DM2 = 0.4
Y: Since 191.25 / 255 × 8 = 6, the distance DY1 between the first point Y1 and Y1 of Y and the distance DY2 between the second points Y2 and Y2 of Y are Y1 = 6 and DY1. = 0.0, Y2 = 7, DY2 = 1.0
Since K: 76.5 / 255 × 8 = 2.4, the distance DK1 between the first points K1 and K1 of K and the distance DK2 between the second points K2 and K2 of K are K1 = 2. , DK1 = 0.4, K2 = 3, and DK2 = 0.6.
[0073]
Also, the CMYK → C2 point (C1, C2) × M2 point (M1, M2) × Y2 point (Y1) from the CMYK → L * a * b * LUT 132 of the printing machine that performed the mapping of the L * a * b * values in S32. , Y2) × K2 points (K1, K2) = 16 points of the L * a * b * color system,
Lc1m1y1k1 *, Lc1m1y1k2 *, Lc1m1y2k1 *,
Lc1m1y2k2 *, Lc1m2y1k1 *,
Lc1m2y1k2 *, Lc1m2y2k1 *, Lc1m2y2k2 *,
Lc2m1y1k1 *, Lc2m1y1k2 *, Lc2m1y2k1 *,
Lc2m1y2k2 *, Lc2m2y1k1 *,
Lc2m2y1k2 *, Lc2m2y2k1 *, Lc2m2y2k2 *,
ac1m1y1k1 *, ac1m1y1k2 *, ac1m1y2k1 *,
ac1m1y2k2 *, ac1m2y1k1 *,
ac1m2y1k2 *, ac1m2y2k1 *, ac1m2y2k2 *,
ac2m1y1k1 *, ac2m1y1k2 *, ac2m1y2k1 *,
ac2m1y2k2 *, ac2m2y1k1 *,
ac2m2y1k2 *, ac2m2y2k1 *, ac2m2y2k2 *,
bc1m1y1k1 *, bc1m1y1k2 *, bc1m1y2k1 *,
bc1m1y2k2 *, bc1m2y1k1 *,
bc1m2y1k2 *, bc1m2y2k1 *, bc1m2y2k2 *,
bc2m1y1k1 *, bc2m1y1k2 *, bc2m1y2k1 *,
bc2m1y2k2 *, bc2m2y1k1 *,
bc2m2y1k2 *, bc2m2y2k1 *, bc2m2y2k2 *
Then, C = 25.5 (2 at 0 to 20), M = 51 (4 at 0 to 20), Y = 191.25 (15 at 0 to 20), K = 76.5 (0 to 20) The value of the L * a * b * color system for 6) is obtained by the following equation.
[0074]
L * = DC2 × DM2 × DY2 × DK2 × Lc1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × Lc1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × Lc1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × Lc1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × Lc1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × Lc1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × Lc1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × Lc1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × Lc2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × Lc2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × Lc2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × Lc2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × Lc2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × Lc2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × Lc2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × Lc2m2y2k2 *
a * = DC2 × DM2 × DY2 × DK2 × ac1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × ac1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × ac1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × ac1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × ac1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × ac1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × ac1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × ac1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × ac2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × ac2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × ac2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × ac2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × ac2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × ac2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × ac2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × ac2m2y2k2 *
b * = DC2 × DM2 × DY2 × DK2 × bc1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × bc1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × bc1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × bc1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × bc1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × bc1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × bc1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × bc1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × bc2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × bc2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × bc2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × bc2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × bc2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × bc2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × bc2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × bc2m2y2k2 *
Becomes
[0075]
(S12)
Next, from the values of the L * a * b * color system obtained in step S11, CMYK is obtained using the L * a * b * → CMYK LUT 136 of the calibration color printer. For example, if the values of the L * a * b * color system determined in step 11 are L * = 57.0, a * = 5.3, and b * = 35.6, L * a * b *: 33 × 33 × 33 → L * a * b * of CMYK LUT: The distance between the input point within 33 × 33 × 33 and each input point of L * a * b * is
Since L *: 57.0 / 100 × 32 = 18.2, the distance DL1 between the first points L1 and L1 of L * and the distance DL2 between the second points L2 and L2 of L are L1 = 18, DL1 = 0.2, L2 = 19, DL2 = 0.8
a *: (5.3 + 127) /255×32=16.6, so the distance Da1 between the first points a1 and a1 of a * and the distance Da2 between the second points a2 and a2 of a are , A1 = 16, Da1 = 0.6, a2 = 17, Da2 = 0.4
Since b *: (35.6 + 127) /255×32=20.4, the distance Db1 between the first points b1 and b1 of b * and the distance Db2 between the second points b2 and b2 of b are , B1 = 20, Db1 = 0.4, b2 = 21, Db2 = 0.6
Becomes
[0076]
L * a * b *: 33 × 33 × 33 → L * 2 points (L1, L2) × a * 2 points (a1, a2) × b * 2 points (b1, b2) = 8 points from the CMYK LUT The CMYK value of
CL1a1b1, CL1a1b2, CL1a2b1, CL1a2b2
CL2a1b1, CL2a1b2, CL2a2b1, CL2a2b2
ML1a1b1, ML1a1b2, ML1a2b1, ML1a2b2,
ML2a1b1, ML2a1b2, ML2a2b1, ML2a2b2
YL1a1b1, YL1a1b2, YL1a2b1, YL1a2b2
YL2a1b1, YL2a1b2, YL2a2b1, YL2a2b2
KL1a1b1, KL1a1b2, KL1a2b1, KL1a2b2
KL2a1b1, KL2a1b2, KL2a2b1, KL2a2b2
Then, the values of CMYK for L * = 57.0, a * = 5.3, and b * = 35.6 are obtained by the following equations.
[0077]
C = DL2 × Da2 × Db2 × CL1a1b1
+ DL2 × Da2 × Db1 × CL1a1b2
+ DL2 × Da1 × Db2 × CL1a2b1
+ DL2 × Da1 × Db1 × CL1a2b2
+ DL1 × Da2 × Db2 × CL2a1b1
+ DL1 × Da2 × Db1 × CL2a1b2
+ DL1 × Da1 × Db2 × CL2a2b1
+ DL1 × Da1 × Db1 × CL2a2b2
M = DL2 × Da2 × Db2 × ML1a1b1
+ DL2 × Da2 × Db1 × ML1a1b2
+ DL2 × Da1 × Db2 × ML1a2b1
+ DL2 × Da1 × Db1 × ML1a2b2
+ DL1 × Da2 × Db2 × ML2a1b1
+ DL1 × Da2 × Db1 × ML2a1b2
+ DL1 × Da1 × Db2 × ML2a2b1
+ DL1 × Da1 × Db1 × ML2a2b2
Y = DL2 × Da2 × Db2 × YL1a1b1
+ DL2 × Da2 × Db1 × YL1a1b2
+ DL2 × Da1 × Db2 × YL1a2b1
+ DL2 × Da1 × Db1 × YL1a2b2
+ DL1 × Da2 × Db2 × YL2a1b1
+ DL1 × Da2 × Db1 × YL2a1b2
+ DL1 × Da1 × Db2 × YL2a2b1
+ DL1 × Da1 × Db1 × YL2a2b2
K = DL2 × Da2 × Db2 × KL1a1b1
+ DL2 × Da2 × Db1 × KL1a1b2
+ DL2 × Da1 × Db2 × KL1a2b1
+ DL2 × Da1 × Db1 × KL1a2b2
+ DL1 × Da2 × Db2 × KL2a1b1
+ DL1 × Da2 × Db1 × KL2a1b2
+ DL1 × Da1 × Db2 × KL2a2b1
+ DL1 × Da1 × Db1 × KL2a2b2
Becomes
[0078]
(S13)
As described above, steps S11 and S12 are repeatedly performed for C × M × Y × K: 21 × 21 × 21 × 21 = 194481 input points, and the result is CMYK 4-dimensional input CMYK 4-dimensional output CMYK → CMYK LUT (1).
[0079]
Next, a method of calculating an output value of a combination of three CMY colors for 21 × 21 × 21 points of a CMY combination of K = 0 of the printing press will be described.
[0080]
(S34)
First, the CMYK value of the calibration color printer for the input value of each combination of CMY21 × 21 × 21 of K = 0 of the printing press is obtained from the above-mentioned CMYK → CMYK LUT (1) and set as the CMYK initial value.
[0081]
(S35)
Next, an L * a * b * value corresponding to the CMYK initial value is obtained by the CMYK → L * a * b * LUT 135 of the proof color printer 2. C = 128, M = 128, Y = 128 are examples of combinations of CMY of K = 0 of the printing press, and the initial values of CMYK obtained by calculating the device link color profile are C = 125, M = 140, Y = 156, K = 33, the distance between the input points in CMYK 9 × 9 × 9 × 9 of the proof color printer 2 → L * a * b * LUT 135 and the respective input points of CMYK is
C: 125/255 × 8 = 3.92, so the distance DC1 between the first points C1 and C1 of C and the distance DC2 between the second points C2 and C2 of C are C1 = 3, DC1 = 0.92, C2 = 4, DC2 = 0.08
Since M: 140/255 × 8 = 4.39, the distance DM1 between the first points M1 and M1 of M and the distance DM2 between the second points C2 and C2 of C are M1 = 4, DM1 = 0.39, M2 = 5, DM2 = 0.61
Since Y: 156/255 × 8 = 4.89, the distance DY1 between the first point Y1 and Y1 of Y and the distance DY2 between the second points Y2 and Y2 of Y are Y1 = 4 and DY1. = 0.89, Y2 = 5, DY2 = 0.11
Since K: 33/255 × 8 = 1.03, the distance DK1 between the first points K1 and K1 of K and the distance DK2 between the second points K2 and K2 of K are K1 = 1, DK1 = 0.03, K2 = 2, and DK2 = 0.97.
[0082]
Here, CMYK of the calibration color printer 2 → C2 point (C1, C2) × M2 point (M1, M2) × Y2 point (Y1, Y2) × K2 point (K1, K2) from the LUT 135 ) = L * a * b * color system values for 16 points
Lc1m1y1k1 *, Lc1m1y1k2 *, Lc1m1y2k1 *,
Lc1m1y2k2 *, Lc1m2y1k1 *,
Lc1m2y1k2 *, Lc1m2y2k1 *, Lc1m2y2k2 *,
Lc2m1y1k1 *, Lc2m1y1k2 *, Lc2m1y2k1 *,
Lc2m1y2k2 *, Lc2m2y1k1 *,
Lc2m2y1k2 *, Lc2m2y2k1 *, Lc2m2y2k2 *,
ac1m1y1k1 *, ac1m1y1k2 *, ac1m1y2k1 *,
ac1m1y2k2 *, ac1m2y1k1 *,
ac1m2y1k2 *, ac1m2y2k1 *, ac1m2y2k2 *,
ac2m1y1k1 *, ac2m1y1k2 *, ac2m1y2k1 *,
ac2m1y2k2 *, ac2m2y1k1 *,
ac2m2y1k2 *, ac2m2y2k1 *, ac2m2y2k2 *,
bc1m1y1k1 *, bc1m1y1k2 *, bc1m1y2k1 *,
bc1m1y2k2 *, bc1m2y1k1 *,
bc1m2y1k2 *, bc1m2y2k1 *, bc1m2y2k2 *,
bc2m1y1k1 *, bc2m1y1k2 *, bc2m1y2k1 *,
bc2m1y2k2 *, bc2m2y1k1 *,
bc2m2y1k2 *, bc2m2y2k1 *, bc2m2y2k2 *
Then, the values of the L * a * b * color system for C = 125, M = 140, Y = 156, and K = 33 are obtained by the following equations.
[0083]
L * = DC2 × DM2 × DY2 × DK2 × Lc1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × Lc1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × Lc1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × Lc1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × Lc1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × Lc1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × Lc1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × Lc1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × Lc2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × Lc2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × Lc2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × Lc2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × Lc2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × Lc2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × Lc2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × Lc2m2y2k2 *
a * = DC2 × DM2 × DY2 × DK2 × ac1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × ac1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × ac1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × ac1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × ac1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × ac1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × ac1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × ac1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × ac2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × ac2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × ac2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × ac2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × ac2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × ac2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × ac2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × ac2m2y2k2 *
b * = DC2 × DM2 × DY2 × DK2 × bc1m1y1k1 *
+ DC2 × DM2 × DY2 × DK1 × bc1m1y1k2 *
+ DC2 × DM2 × DY1 × DK2 × bc1m1y2k1 *
+ DC2 × DM2 × DY1 × DK1 × bc1m1y2k2 *
+ DC2 × DM1 × DY2 × DK2 × bc1m2y1k1 *
+ DC2 × DM1 × DY2 × DK1 × bc1m2y1k2 *
+ DC2 × DM1 × DY1 × DK2 × bc1m2y2k1 *
+ DC2 × DM1 × DY1 × DK1 × bc1m2y2k2 *
+ DC1 × DM2 × DY2 × DK2 × bc2m1y1k1 *
+ DC1 × DM2 × DY2 × DK1 × bc2m1y1k2 *
+ DC1 × DM2 × DY1 × DK2 × bc2m1y2k1 *
+ DC1 × DM2 × DY1 × DK1 × bc2m1y2k2 *
+ DC1 × DM1 × DY2 × DK2 × bc2m2y1k1 *
+ DC1 × DM1 × DY2 × DK1 × bc2m2y1k2 *
+ DC1 × DM1 × DY1 × DK2 × bc2m2y2k1 *
+ DC1 × DM1 × DY1 × DK1 × bc2m2y2k2 *
Becomes
[0084]
(S36)
Further, using the CMY → L * a * b * LUT from which values of CMY9 × 9 × 9 of K = 0 of the color printer for calibration are extracted, the L * a * b * color system of Determine the value of CMY.
[0085]
FIG. 22 is a plot of L * on the vertical axis and a * on the horizontal axis, for a two-dimensional 9 × 9 combination of M and C of CMY9 × 9 × 9 (Y = 0). Although it is actually three-dimensional, it is shown in two dimensions for simplicity. For this CMY distribution, L * a * b * of the target point to be obtained is given as a target value T '. In this case, when the target value T ′ is in the area surrounded by the lattice points a ′ to d ′ as shown in FIG. 22, the combination of MCs (the target value T) in the MC coordinate system is It is presumed that it is in the area surrounded by points a to d. Then, where the target value T is located in the region formed by the lattice points a to d is obtained by performing convergence calculation processing while associating the color system of FIG. 22 with the coordinate system of FIG. The convergence calculation process is performed in such a way that, although the conversion from the coordinate system of FIG. 23 to the color system of FIG. 22 is known, the reverse conversion is very complicated and a good conversion formula is still obtained. Is not known.
[0086]
Region SP formed by lattice points a to d in FIG.₀To four areas SP₁~ SP₄Divide equally. The five division points e to i are calculated by weighted averaging using surrounding grid points that have already been obtained. Then, the values obtained by converting the values corresponding to the division points e to i into the L * a * b * color system are plotted in the color system of FIG. 12, and formed by the plotted division points e ′ to i ′. Four areas SP₁’-SP₄In which region the target value T 'is located. As shown in FIG.₂′, The target value T is in the region SP as shown in FIG.₂’Area SP₂It is estimated that there is.
[0087]
Next, the estimated area SP₂To four areas SP₅~ SP₈Divide equally. The five division points j to n are calculated by weighted averaging using the already obtained surrounding grid points and division points. Then, values obtained by converting the values corresponding to the division points j to n into the L * a * b * color system are plotted in the color system of FIG. 12, and the plotted division points j ′ to n ′ are used. Four areas SP formed₅’-SP₈In which region the target value T 'is located. As shown in FIG.₈′, The target value T is in the region SP as shown in FIG.₈’Area SP₈It is estimated that there is.
[0088]
Next, the estimated area SP₈To four areas SP₉~ SP₁₂Divide equally. The five division points o to s are calculated by weighted averaging using surrounding grid points and division points that have already been obtained. Then, values obtained by converting the values corresponding to the division points o to s into the L * a * b * color system are plotted in the color system of FIG. 12, and the plotted division points o ′ to s ′ are used. Four areas SP formed₉’-SP₁₂In which region the target value T 'is located. As shown in FIG.₁₀′, The target value T is in the region SP as shown in FIG.₁₀’Area SP₁₀It is estimated that there is.
[0089]
By repeating such division of the area, the grid gradually becomes smaller and finally converges. Then, by averaging the four grid points or division points forming the converged region, a combination of the target value T, that is, the basic color indicating the output color to be obtained is obtained.
[0090]
Although the method based on the convergence calculation has been described as an example, an interpolation processing method as described in the specification of Japanese Patent No. 2895086 by the present applicant may be used.
[0091]
When the target value T 'is outside the color reproduction range formed by the vertices W', C ', M', and B 'of the L * a * b * color system as shown in FIG. The value T 'needs to be moved within the color reproduction range. In this case, the target value T ′ is moved in the achromatic direction as shown in FIG. 24, and the coordinates of the intersection between the straight line in the achromatic direction and the boundary of the color reproduction range are set to the target value T ′ as shown in FIG. I do. Then, a target value T corresponding to the target value T 'is calculated as shown in FIG. Note that the target value T 'does not necessarily need to be moved to the boundary, but may be moved within the color reproduction range.
[0092]
Here, an example of a C × M two-dimensional is shown for the sake of explanation. However, actually, a three-dimensional C × M × Y is performed, and the values of the L * a * b * color system obtained in step S33 are obtained. CMY values of the CMY are obtained, and the CMY three-color parameters output by the color printer 2 for calibration are output by the color printer 2 for the colors output by the printing machine by the combination of CMY of 21 × 21 × 21 points of the CMY of K = 0 of the printing press. CMY → CMY LUT associated with the combination of
[0093]
(S37)
The K gradation correction curve 134 for correcting the K of the printing press obtained as described above to the calibration color printer K, and the calibration for each combination (21 × 21 × 21) of CMY when K = 0 of the printing press. The device link color profile is re-created using the CMY (21 × 21 × 21) CMY → CMY LUT of the color printer.
[0094]
The K gradation correction curve 134 is Kout = f [Kin (0-20)], and the CMY → CMY LUT is Cout = CoutLUT [Cin (0-20), Min (0-20), Yin (0-20) )]
Mout = MoutLUT [Cin (0-20), Min (0-20), Yin (0-20)]
Yout = YoutLUT [Cin (0-20), Min (0-20), Yin (0-20)]
Then, each input point of CMYK21 × 21 × 21 × 21 of the device link color profile is set to Cin, Min, Yin, and Kin, Kout = f [Kin (0 to 20)], and Cout = CoutLUT [Cin (0 to 20), Min (0 to 20), Yin (0 to 20)]
Mout = MoutLUT [Cin (0-20), Min (0-20), Yin (0-20)]
Yout = YoutLUT [Cin (0-20), Min (0-20), Yin (0-20)]
Thus, Cout, Mout, Yout, and Kout for each input point are obtained, converted into an LUT, and re-created as a final device link color profile CMYK → CMYK LUT 137.
[0095]
(S103)
This device link color profile CMYK → CMYK LUT 137 converts the CMYK gradations of the image data one pixel at a time and performs color adjustment. Then, the converted image data is transmitted to the proof color printer 2, and the proof color printer 2 outputs an image based on the transmitted image data.
[0096]
For example, if the pixels of the image data are C = 25, M = 51, Y = 191, K = 10, CMYK: 21 × 21 × 21 × 21 → CMYK of the CMYK LUT 137: 21 × 21 × 21 × 21 The distance between the input point and each input point of CMYK is
Since C: 25/255 × 20 = 1.96, the distance DC1 between the first points C1 and C1 of C and the distance DC2 between the second points C2 and C2 of C are C1 = 1, DC1 = 0.96, C2 = 2, DC2 = 0.04
Since M: 51/255 × 20 = 4.0, the distance DM1 between the first point M1 and M1 of M and the distance DM2 between the second points M2 and M2 of M are M1 = 4, DM1 = 0.0, M2 = 5, DM2 = 1.0
Y: Since 191/255 × 20 = 14.98, the distance DY1 between the first point Y1 of Y and Y1 and the distance DY2 between the second point Y2 and Y2 of Y are Y1 = 14, DY1. = 0.98, Y2 = 15, DY2 = 0.02
Since K: 10/255 × 20 = 0.78, the distance DK1 between the first points K1 and K1 of K and the distance DK2 between the second points K2 and K2 of K are K1 = 0, DK1 = 0.78, K2 = 1, and DK2 = 0.22.
[0097]
The CMYK output values for C2 point (C1, C2) × M2 point (M1, M2) × Y2 point (Y1, Y2) × K2 point (K1, K2) = 16 points from CMYK → CMYK LUT
Cc1m1y1k1, Cc1m1y1k2, Cc1m1y2k1,
Cc1m1y2k2, Cc1m2y1k1, Cc1m2y1k2,
Cc1m2y2k1, Cc1m2y2k2, Cc2m1y1k1,
Cc2m1y1k2, Cc2m1y2k1, Cc2m1y2k2,
Cc2m2y1k1, Cc2m2y1k2, Cc2m2y2k1,
Cc2m2y2k2,
Mc1m1y1k1, Mc1m1y1k2, Mc1m1y2k1,
Mc1m1y2k2, Mc1m2y1k1, Mc1m2y1k2,
Mc1m2y2k1, Mc1m2y2k2, Mc2m1y1k1,
Mc2m1y1k2, Mc2m1y2k1, Mc2m1y2k2,
Mc2m2y1k1, Mc2m2y1k2, Mc2m2y2k1,
Mc2m2y2k2,
Yc1m1y1k1, Yc1m1y1k2, Yc1m1y2k1,
Yc1m1y2k2, Yc1m2y1k1, Yc1m2y1k2,
Yc1m2y2k1, Yc1m2y2k2, Yc2m1y1k1,
Yc2m1y1k2, Yc2m1y2k1, Yc2m1y2k2,
Yc2m2y1k1, Yc2m2y1k2, Yc2m2y2k1,
Yc2m2y2k2,
Kc1m1y1k1, Kc1m1y1k2, Kc1m1y2k1,
Kc1m1y2k2, Kc1m2y1k1, Kc1m2y1k2,
Kc1m2y2k1, Kc1m2y2k2, Kc2m1y1k1,
Kc2m1y1k2, Kc2m1y2k1, Kc2m1y2k2,
Kc2m2y1k1, Kc2m2y1k2, Kc2m2y2k1,
Kc2m2y2k2,
Then, the CMYK output values for the pixels of C = 25, M = 51, Y = 191, and K = 10 can be obtained as Ctrs, Mtrs, Ytrs, and Ktrs by the following equations.
[0098]
Ctrs = DC2 × DM2 × DY2 × DK2 × Cc1m1y1k1
+ DC2 × DM2 × DY2 × DK1 × Cc1m1y1k2
+ DC2 × DM2 × DY1 × DK2 × Cc1m1y2k1
+ DC2 × DM2 × DY1 × DK1 × Cc1m1y2k2
+ DC2 × DM1 × DY2 × DK2 × Cc1m2y1k1
+ DC2 × DM1 × DY2 × DK1 × Cc1m2y1k2
+ DC2 × DM1 × DY1 × DK2 × Cc1m2y2k1
+ DC2 × DM1 × DY1 × DK1 × Cc1m2y2k2
+ DC1 × DM2 × DY2 × DK2 × Cc2m1y1k1
+ DC1 × DM2 × DY2 × DK1 × Cc2m1y1k2
+ DC1 × DM2 × DY1 × DK2 × Cc2m1y2k1
+ DC1 × DM2 × DY1 × DK1 × Cc2m1y2k2
+ DC1 × DM1 × DY2 × DK2 × Cc2m2y1k1
+ DC1 × DM1 × DY2 × DK1 × Cc2m2y1k2
+ DC1 × DM1 × DY1 × DK2 × Cc2m2y2k1
+ DC1 × DM1 × DY1 × DK1 × Cc2m2y2k2
Mtrs = DC2 × DM2 × DY2 × DK2 × Mc1m1y1k1
+ DC2 × DM2 × DY2 × DK1 × Mc1m1y1k2
+ DC2 × DM2 × DY1 × DK2 × Mc1m1y2k1
+ DC2 × DM2 × DY1 × DK1 × Mc1m1y2k2
+ DC2 × DM1 × DY2 × DK2 × Mc1m2y1k1
+ DC2 × DM1 × DY2 × DK1 × Mc1m2y1k2
+ DC2 × DM1 × DY1 × DK2 × Mc1m2y2k1
+ DC2 × DM1 × DY1 × DK1 × Mc1m2y2k2
+ DC1 × DM2 × DY2 × DK2 × Mc2m1y1k1
+ DC1 × DM2 × DY2 × DK1 × Mc2m1y1k2
+ DC1 × DM2 × DY1 × DK2 × Mc2m1y2k1
+ DC1 × DM2 × DY1 × DK1 × Mc2m1y2k2
+ DC1 × DM1 × DY2 × DK2 × Mc2m2y1k1
+ DC1 × DM1 × DY2 × DK1 × Mc2m2y1k2
+ DC1 × DM1 × DY1 × DK2 × Mc2m2y2k1
+ DC1 × DM1 × DY1 × DK1 × Mc2m2y2k2
Ytrs = DC2 × DM2 × DY2 × DK2 × Yc1m1y1k1
+ DC2 × DM2 × DY2 × DK1 × Yc1m1y1k2
+ DC2 × DM2 × DY1 × DK2 × Yc1m1y2k1
+ DC2 × DM2 × DY1 × DK1 × Yc1m1y2k2
+ DC2 × DM1 × DY2 × DK2 × Yc1m2y1k1
+ DC2 × DM1 × DY2 × DK1 × Yc1m2y1k2
+ DC2 × DM1 × DY1 × DK2 × Yc1m2y2k1
+ DC2 × DM1 × DY1 × DK1 × Yc1m2y2k2
+ DC1 × DM2 × DY2 × DK2 × Yc2m1y1k1
+ DC1 × DM2 × DY2 × DK1 × Yc2m1y1k2
+ DC1 × DM2 × DY1 × DK2 × Yc2m1y2k1
+ DC1 × DM2 × DY1 × DK1 × Yc2m1y2k2
+ DC1 × DM1 × DY2 × DK2 × Yc2m2y1k1
+ DC1 × DM1 × DY2 × DK1 × Yc2m2y1k2
+ DC1 × DM1 × DY1 × DK2 × Yc2m2y2k1
+ DC1 × DM1 × DY1 × DK1 × Yc2m2y2k2
Ktrs = DC2 × DM2 × DY2 × DK2 × Kc1m1y1k1
+ DC2 × DM2 × DY2 × DK1 × Kc1m1y1k2
+ DC2 × DM2 × DY1 × DK2 × Kc1m1y2k1
+ DC2 × DM2 × DY1 × DK1 × Kc1m1y2k2
+ DC2 × DM1 × DY2 × DK2 × Kc1m2y1k1
+ DC2 × DM1 × DY2 × DK1 × Kc1m2y1k2
+ DC2 × DM1 × DY1 × DK2 × Kc1m2y2k1
+ DC2 × DM1 × DY1 × DK1 × Kc1m2y2k2
+ DC1 × DM2 × DY2 × DK2 × Kc2m1y1k1
+ DC1 × DM2 × DY2 × DK1 × Kc2m1y1k2
+ DC1 × DM2 × DY1 × DK2 × Kc2m1y2k1
+ DC1 × DM2 × DY1 × DK1 × Kc2m1y2k2
+ DC1 × DM1 × DY2 × DK2 × Kc2m2y1k1
+ DC1 × DM1 × DY2 × DK1 × Kc2m2y1k2
+ DC1 × DM1 × DY1 × DK2 × Kc2m2y2k1
+ DC1 × DM1 × DY1 × DK1 × Kc2m2y2k2
Becomes
[0099]
According to the device link color profile, the K amount of the printing press is output by the calibration color printer 2 by conversion only for gradation correction. When the device link color profile is created, K = 0 and CMY = (maximum value) of the printing press L * a * b * values of K = 0 and CMY = (maximum value) of L * a * b * values of the color printer for calibration 2 are created, and a CMY → CMY LUT of K = 0 is created. When the CMY of the printing press is at the maximum value, the proofreading color printer 2 outputs the CMY at the maximum value.
[0100]
However, due to a calculation error in the calculation process or the like, there is a case where the CMY on the output side becomes smaller than the maximum value when the CMY of the device link color profile CMYK → CMYK LUT 137 has the maximum value. In such a case, As shown in FIG. 27, after the device link color profile CMYK → CMYK LUT 137 is created as described above, correction for changing the output side CMY to the maximum value may be performed. Further, in that case, in order to eliminate a tone jump or the like, the surrounding points may be changed along with the change to the maximum value of CMY. Thus, when the CMY has the maximum value, the proofreading color printer 2 reliably outputs the CMY with the maximum value.
[0101]
Also, a small amount of C, M, and Y other than K may be included in the K single-color portion due to a calculation error in the calculation process or the like. In such a case, as shown in FIG. After creating the link color profile CMYK → CMYK LUT 137, a correction for changing the output side CMY to 0 may be made. Further, in that case, in order to eliminate a tone jump or the like, the surrounding points may be changed along with the change to the maximum value of CMY. As a result, the K single color is reliably output by the calibration color printer 2 without turbidity. However, when C, M, and Y, which enter a small amount in addition to K in the color printer 2 for proofing, are a white background of the printed matter (C = M = Y = K = 0 of the printing press), the proofing color printer is used as it is. In step 2, a white background of the printed matter can be reproduced.
[0102]
As described above, according to the present embodiment, the second color profile (device color profile) is obtained from the first color profile (device color profile) of the printing press and the first color profile (device color profile) of the proof color printer. Device Link Color Profile) is created, the output value is set separately for K single color and CMY three colors, and output with a color printer for calibration, so that K single color will not be replaced by CMYK four colors, so the amount of K plate Can obtain the result that the character quality is good and the moire pattern or the rosette pattern is not much different from the printed matter of the printing press, and the CMY is the maximum value when the CMY is the maximum value. Can be output in solid.
[0103]
[Second embodiment]
Next, a second embodiment according to the present invention will be described. In the following, a detailed description of the configuration substantially the same as that of the first embodiment will be omitted, and different points will be mainly described.
[0104]
This embodiment is different from the above-described color adjustment method in that a device link color profile is generated and converted so that color reproducibility is further improved when K is overprinted in a large amount (high gradation). It is in.
[0105]
For this purpose, in the present embodiment, in the device link color profile creation step shown in S102 of FIG. 2 of the first embodiment, the combination of CMYK of the Creates a K gradation correction curve 134 from the device color profile of the printing press and the device color profile of the calibration color printer 2, converts the K gradation correction curve 134 using the K gradation correction curve 134, and obtains CMY. Is the L * a * b * value corresponding to at least the combination of the maximum values of CMY in the device color profile of the printing press, and the combination of the maximum value of CMY with the corrected K in the device color profile of the proof color printer 2. CM of the printing press mapped to L * a * b * values corresponding to It determined using the K → L * a * b * LUT132, to create a device-link color profile (described in detail later).
[0106]
Hereinafter, the content of the above-described device link color profile and a method of creating the profile will be described in detail.
[0107]
The device link color profile is, for example, a four-dimensional input / four-dimensional output LUT in which CMYK values are input for LUT input points of C × M × Y × K: 21 × 21 × 21 × 21 = 194481 as shown in FIG. Yes, it is created using the device color profile of the printing press and the proofreading color printer 2, for example, according to the procedure shown in the flowchart of FIG.
[0108]
(S41)
First, a K gradation correction curve 134 is created in the same manner as described in S31 of FIG.
[0109]
(S42)
Here, the L * a * b * value for the combination of CMYK → L * a * b * LUT of the printing press and the L * a * b * value for the combination of CMY at least the maximum value are the calibration color printer 2. 20 so that CMYK at K (Kcps) obtained by correcting K of CMYK of the printing machine by the gradation correction curve 134 matches the L * a * b * value for the maximum value combination.
[0110]
For that purpose, first, Kcps is obtained by correcting K of CMYK of the printing machine by the gradation correction curve 134.
[0111]
Next, an L * a * b * value for a combination of the maximum values of CMY in Kcps is obtained. Taking the case of K = 101 as an example, 101 is C × M × Y × K: 9 points of 9 × 9 × 9 × 9 K (0, 32, 64, 96, 128, 159, 191, 223, 255) between the fourth 96 and the fifth 128, C = M = Y = 255 (9th point) and K = 96 (4 points) in 9 × 9 × 9 × 9 points. L * a * b * value at point (point) and point L * a * b * value at C = M = Y = 255 (9th point) and K = 128 (5th point) Calculate by interpolation.
[0112]
The weight w4 for L4 * a4 * b4 *, which is the L * a * b * value of C = M = Y = 255 (the ninth point) and K = 96 (the fourth point),
w4 = 1.0- (101-96) / (128-96)
The weight w5 for L5 * a5 * b5 * which is the L * a * b * value of C = M = Y = 255 (the ninth point) and K = 128 (the fifth point)
If w5 = (101-96) / (128-96),
L1a1b1, which is the L * a * b * value after interpolation, is
L1 = w4 × L4 * + w5 × L5 *,
a1 = w4 × a4 * + w5 × a5 *,
b1 = w4 × b4 * + w5 × b5 *,
Required by
[0113]
FIG. 20 is a cross-sectional view of a low lightness portion close to the CMY maximum value of the CMY color space at K in the CMYK color space of the printing press, and the CMY maximum value of the CMY color space of K = Kcps of the proof color printer 2. Is a cross-sectional view of a low lightness portion near L, with L * on the vertical axis and a * on the horizontal axis. Although shown in two dimensions for simplicity, it is actually three dimensional, and mapping is performed for b * as follows.
[0114]
The movement of the L * a * b * value with respect to the combination of the maximum values of CMY is such that the CMY of the printing press sets the maximum L * a * b * value (L0, a0, b0) to the maximum of CMY of the color printer 2 for calibration. The value is mapped to the L * a * b * value (L1, a1, b1). However, in the present embodiment, the L value is smaller than Lfix shown in FIG. 20, for example, so that the L * a * b * value after the movement maintains continuity. For example, the L * a * b * value before the mapping is set to (L, a, b) and the L * a * b * value after the mapping is set to (f (L), f (a), f (b)),
f (L) = L − {(Lfix−L) / (Lfix−L0)} × (L0−L1), f (a) = a − {(Lfix−L) / (Lfix−L0)} × (a0 −a1), f (b) = b − {(Lfix−L) / (Lfix−L0)} × (b0−b1), where L ≦ Lfix,
Map according to This is performed for each K of the combination of CMYK of the printing press.
[0115]
(S43)
Next, using the CMYK → L * a * b * LUT 132 of the printing press that has performed the mapping of the L * a * b * values in S42 and the L * a * b * → CMYK LUT 136 of the color printer 2 for calibration, C × M × Y × K: 21 × 21 × 21 × 21 = 194481 points of a combination of 21 points obtained by equally dividing 0 to 255 into 20 as shown in FIG. For example, a four-dimensional input / four-dimensional output CMYK → CMYK LUT (1) in which the CMYK values to be output to the calibration color printer 2 for each point are entered as the output values is shown in FIG. The calculation is performed according to the procedure from S11 to S13.
[0116]
Next, a method of calculating the output value of K and the output value of a combination of three colors of CMY for CMYK 21 × 21 × 21 × 21 points of the printing press will be described.
[0117]
(S44)
First, the CMYK values of the above-mentioned CMYK → CMYK LUT (1) calibration color printers for the input values of each combination of CMYK: 21 × 21 × 21 × 21 are set as CMYK initial values, and An L * a * b * value corresponding to the CMYK initial value is obtained by the CMYK → L * a * b * LUT 135 in the same manner as described in S35 of FIG. 17 of the first embodiment.
[0118]
(S45)
Here, K of the combination of CMYK of the printing machine corresponding to the CMYK initial value is corrected using the gradation correction curve 134, and Kcps is obtained.
[0119]
(S46)
Further, using the CMY → L * a * b * LUT from which values of CMY9 × 9 × 9 of K = Kcps of the color printer for calibration are extracted, the L * a * b * color system of The values are converted to CMY values. First, CMY → L * a * b * LUT at K = Kcps is performed as follows.
[0120]
For example, in the case of C = M = Y = 191, the L * a * b * value for the CMY combination when Kcps = 101 is 101 × C × M × Y × K: 9 × 9 × Since it is between the fourth 96 and the fifth 128 of 9 points of 9 × 9 K (0, 32, 64, 96, 128, 159, 191, 223, 255), 9 × 9 × L * a * b * values of C = M = Y = 191 (7th point) and K = 96 (4th point) among 9 × 9 points, and C = M = Y = 191 (7 points) Eye), K = 128 (fifth point), and the point L * a * b * value.
[0121]
The weight w1 for L1 * a1 * b1 * that is the L * a * b * value of C = M = Y = 191 (7th point) and K = 96 (4th point)
w1 = 1.0- (101-96) / (128-96)
The weight w2 for L2 * a2 * b2 * that is the L * a * b * value of C = M = Y = 191 (7th point) and K = 128 (5th point)
If w2 = (101-96) / (128-96),
Lm * am * bm * which is the L * a * b * value after interpolation is
Lm * = w1 × L1 * + w2 × L2 *,
am * = w1 × a1 * + w2 × a2 *,
bm * = w1 × b1 * + w2 × b2 *,
Required by
[0122]
By performing this for C × M × Y: 9 × 9 × 9 = 729 points, CMY → L which is the L * a * b * value of CMY9 × 9 × 9 of K = Kcps of the color printer for calibration 2. A * a * b * LUT is required.
[0123]
Then, the CMY combination for the L * a * b * value obtained in S44 is determined using the CMY → L * a * b * LUT at K = Kcps in S36 in FIG. 17 of the first embodiment. Obtain in the same way as described.
[0124]
(S47)
Then, the CMYK value of the calibration color printer of the CMYK → CMYK LUT (1) is replaced with CMY obtained in S46, K is replaced with Kcps obtained in S45, and the LUT-converted and re-created one is obtained. The device link color profile is changed from CMYK to CMYK LUT 137.
[0125]
According to this device link color profile, the K amount of the printing press is output by the calibration color printer 2 by conversion only for gradation correction, and when the device link color profile is created, L * a of CMY = (maximum value) of the printing press is used. The * b * value is created by mapping the K of the combination of CMY of the calibration color printer 2 to the L * a * b * value of CMY = (maximum value) in Kcps converted by the gradation correction curve. By calculating the combination of CMY using the CMY → L * a * b * LUT in Kcps converted by the correction curve, when the CMY of the printing press has the maximum value, the CMY is output by the calibration color printer 2 at the maximum value. Is done.
[0126]
Further, since the combination of CMY with respect to the combination of CMYK of the printing press is obtained from the CMY → L * a * b * LUT in K obtained by converting K with the gradation correction curve, a large amount of K is printed particularly on CMY. Color accuracy in the case of color can be improved.
[0127]
In the same manner as in the first embodiment, due to a calculation error in the calculation process or the like, CMY on the output side becomes smaller than the maximum value with respect to the input of the maximum value of CMY. When a small amount of M and Y is included, the correction described in the first embodiment with reference to FIGS. 27 and 28 may be performed.
[0128]
However, C, M, and Y, which enter a small amount in addition to K in the color printer 2 for proofing, vary from K to C * → L * a * b * LUT in K obtained by converting K with a gradation correction curve. is there. In such a case, in order to reproduce the white background of the printed matter (C = M = Y = K = 0 of the printing press), the values of C, M, and Y are changed to C = M = Y of the printing press as shown in FIG. By changing the values of C, M, and Y with respect to = K = 0, the white background of the printed matter can be reproduced by the proofreading color printer 2.
[0129]
As described above, according to the present embodiment, similarly to the first embodiment, the amount of the K plate is not much different from the printed matter of the printing press, the character quality is good, and the moire pattern and the rosetta pattern are When the CMY has the maximum value, the CMY can be output in the solid value of the maximum value. In addition, when the color in which the K is overprinted in a large amount on the CMY can be obtained. Color accuracy can be improved.
[0130]
[Third Embodiment]
Next, a third embodiment according to the present invention will be described. In the following, a detailed description of a configuration substantially the same as that of the second embodiment will be omitted, and different points will be mainly described.
[0131]
This embodiment is different from the color adjustment method of the second embodiment in that a device link color profile is converted and converted so as to further improve the color reproducibility when the color is high in saturation.
[0132]
When the CMY value in Kcps is obtained from the L * a * b * value by the method described in the second embodiment, if the L * a * b * value is outside the CMY color range, the L * Since the a * b * values are moved, color reproducibility may be poor. In order to further enhance the color reproducibility in such a case, it is effective to calculate the CMY values in Kcps from L * a * b * in a low chroma color space. That is, since many points outside the color range have high saturation, K and CMY are obtained and replaced by the method described in the second embodiment where the saturation is low, but where the saturation is high, By avoiding replacement, color reproducibility can be further improved.
[0133]
For this reason, in the present embodiment, in the device link color profile creation step shown in S102 of FIG. 2 of the second embodiment, only when the saturation of the output color for the combination of CMYK is low, S47 of FIG. The CMYK values are replaced (details will be described later).
[0134]
Hereinafter, the content of the above-described device link color profile and a method of creating the profile will be described in detail.
[0135]
The device link color profile is, for example, a four-dimensional input / four-dimensional output LUT in which CMYK values are input for LUT input points of C × M × Y × K: 21 × 21 × 21 × 21 = 194481 as shown in FIG. Yes, it is created using the device color profile of the printing press and the color printer 2 for proofing, for example, according to the procedure shown in the flowchart of FIG.
[0136]
(S51)
First, a K gradation correction curve 134 is created in the same manner as described in S31 of FIG.
[0137]
(S52)
Here, the L * a * b * value for the combination of CMYK → L * a * b * LUT of the printing press and the L * a * b * value for the combination of CMY at least the maximum value are the calibration color printer 2. FIG. 29 of the second embodiment so that the CMY in K (Kout) obtained by converting the K of CMYK of the printing machine by the gradation correction curve 134 matches the L * a * b * value for the maximum value combination. Are mapped in the same manner as in S42.
[0138]
(S53)
Next, using the CMYK → L * a * b * LUT 132 of the printing press that performed the mapping of the L * a * b * values in S52 and the L * a * b * → CMYK LUT 136 of the color printer 2 for calibration, C × M × Y × K: 21 × 21 × 21 × 21 = 194481 points of a combination of 21 points obtained by equally dividing 0 to 255 into 20 as shown in FIG. For example, a four-dimensional input / four-dimensional output CMYK → CMYK LUT (1) in which the CMYK values to be output to the calibration color printer 2 for each point are entered as the output values is shown in FIG. The calculation is performed according to the procedure from S11 to S13.
[0139]
Next, a method of calculating the output value of K and the output value of a combination of three colors of CMY for CMYK 21 × 21 × 21 × 21 points of the printing press will be described.
[0140]
(S54)
First, the CMYK values of the above-mentioned CMYK → CMYK LUT (1) calibration color printers for the input values of each combination of CMYK: 21 × 21 × 21 × 21 are set as CMYK initial values, and An L * a * b * value corresponding to the CMYK initial value is obtained by the CMYK → L * a * b * LUT 135 in the same manner as described in S35 of FIG. 17 of the first embodiment.
[0141]
(S55)
Here, similarly to the description of S45 in FIG. 29 of the second embodiment, K of the combination of CMYK of the printing press corresponding to the CMYK initial value is converted using the gradation correction curve 134, and Kcps is obtained.
[0142]
(S56)
Next, a combination of CMY for the L * a * b * values obtained in S44 is obtained in the same manner as described in S46 of FIG. 29 of the second embodiment.
[0143]
(S57)
Then, the CMYK values of the color printer for calibration of the CMYK → CMYK LUT (1) are replaced with CMY obtained in S56 and K is replaced with Kcps obtained in S55 as follows.
[0144]
First, among the input points of C × M × Y × K: 21 × 21 × 21 × 21, when K = 0, CMY is replaced with CMY obtained in S56, and K is replaced with Kout obtained in S55. replace. In other cases, when the initial value of the CMYK output value is C1M1Y1K1 and the combination of CMY obtained by S56 in C56 and CMYK by Kcps obtained in S55 is C2M2Y2K2, the initial value of CMYK is L * a *. According to the values of the saturation C * and the hue hab obtained from the b * value, when the saturation is small in the hue, the color is replaced with C2M2Y2K2, and when the saturation is large, C1M1Y1K1 is maintained. In order to eliminate a tone jump or the like, replacement is performed as shown below.
[0145]
The saturation C * and the hue hab are obtained from a * b * by the following equations.
C * = (a *²+ B *²)^0.5
hab = Arctan (a * / b *) / π × 180
However, when the right side is negative, it is set as hab = Arctan (a * / b *) / π × 180 + 360.
[0146]
Then, the values of CMYK of the calibration color printer of the CMYK → CMYK LUT (1) are replaced with Cout, Mout, Yout, and Kout obtained by the following equation.
Cout = C1 × w + C2 × (1-w)
Mout = M1 × w + M2 × (1-w)
Yout = Y1 × w + Y2 × (1-w)
Kout = K1 × w + K2 × (1-w)
The above w is obtained, for example, as follows. Using the LUT of C × M × Y: 9 × 9 × 9 → L * a * b * obtained in S46 of FIG. 29, the 9 steps of CMY are classified into 0, 1, 2, 3, 4, 5, 6, When expressed by 7 and 8, C * and hab are obtained from a * b * in the order of C0M8Y0 → C0M8Y8 → C0M0Y8 → C8M0Y8 → C8M0Y0 → C8M8Y0 → C0M8Y0, and the value of C * for hab is obtained based on that. Let the maximum value of C * for each hab be C * max. FIG. 32 shows C * max for each hab.
[0147]
From hab and C * obtained from the L * a * b * values of the CMYK initial values, from the C * value and the C * maximum value for that hab,
w = 1.0− (C * −C * max × 0.25) / (C * max−C * max × 0.25) where w = 1.0 when the right side is 1.0 or more
And
[0148]
The CMYK-> CMYK LUT (1) is replaced with Cout, Mout, Yout, and Kout, which are obtained by the following equation, from the CMYK value of the color printer for calibration, and the LUT is re-created to be the final device link color profile CMYK-> CMYK. LUT 137.
[0149]
According to the device link color profile, the color reproducibility at a high saturation can be further improved.
[0150]
【The invention's effect】
As described above, according to the color adjustment method of the present invention, the color of an image based on image data output by a printing press is targeted, and when the image is output by a proof color printer, the target color is output. When the combination of the parameters of the four basic colors (C, M, Y, K) of the image data is converted using a color profile (CMYK → CMYK LUT) so that the image data is output, the image data is output in K single color by the printing press. The area to be converted is converted so as to be output as a single color of K without mixing halftone dots of other colors even in the color printer for calibration, and is output in a solid color of three colors (C, M, Y) by the printing press. A color adjustment method capable of converting an area so as to be output as three-color solids without adding halftone dots even in a proof color printer, a program for executing this color adjustment method, and the like. It can provide a recording medium storing the program.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing an embodiment according to the present invention.
FIG. 2 is a flowchart illustrating a procedure of a color adjustment method for a printing press and a calibration color printer using a device link color profile according to the first embodiment.
FIG. 3 is an explanatory diagram of an LUT for converting a combination of CMYK into a color system value L * a * b * in the first embodiment.
FIG. 4 is a diagram showing an example of a color patch image for measuring L * a * b * values of colors for CMYK combinations in the first embodiment.
FIG. 5 is a diagram showing a distribution of sample points and interpolated points on a trajectory based on CMY and color system values in the first embodiment.
FIG. 6 is a diagram showing the order of interpolation processing when converting a CMY combination into a color system value in the first embodiment.
FIG. 7 is an explanatory diagram of an LUT for converting a color system value L * a * b * into a combination of CMYK in the first embodiment.
FIG. 8 is a flowchart of a procedure for obtaining a three-dimensional input / four-dimensional output LUT of L * a * b * → CMYK LUT in the first embodiment.
FIG. 9 is a coordinate diagram showing a target value T ′ in the coordinates of the C and M color systems in the first embodiment.
FIG. 10 is a coordinate diagram showing a target value T in coordinates of a combination of C and M colors in the first embodiment.
FIG. 11 is a coordinate diagram of a convergence calculation process for estimating a target value T at coordinates of a combination of C and M colors in the first embodiment.
FIG. 12 is a coordinate diagram of a convergence calculation process for estimating a target value T ′ in coordinates of C and M color systems in the first embodiment.
FIG. 13 is a diagram illustrating a target value T ′ in the coordinates of the C and M color systems when the target value T ′ is outside the color reproduction range in the first embodiment.
FIG. 14 is a coordinate diagram showing the target value T ′ in the coordinates of the C and M color systems when the target value T ′ is outside the color reproduction range in the first embodiment. FIG. 9 is a coordinate diagram showing that the image is moved within the color reproduction range.
FIG. 15 is a diagram showing a target value T at coordinates of a combination of C and M colors when a target value T ′ outside the color reproduction range is moved into the color reproduction range in the first embodiment. It is.
FIG. 16 is an explanatory diagram of an LUT for converting a CMYK combination of a printing press into a CMYK combination of a proof color printer in the first embodiment.
FIG. 17 is a flowchart illustrating a procedure for creating a device link color profile according to the first embodiment.
FIG. 18 is a diagram illustrating nine levels of L * of K single color of the printing press and nine levels of L * of K single color of the calibration color printer at the K gradation level in the first embodiment.
FIG. 19 is a diagram showing a gradation correction curve of K which is an output value for each input value of K in the first embodiment.
FIG. 20 is a cross section of the CMY color space for explaining the mapping of the maximum CMY value of the CMY of the printing press to the L * a * b * value of the color printer for calibrating the maximum value of the CMY. It is a figure showing signs of movement in coordinates of a color system of a figure.
FIG. 21 is a flowchart illustrating a procedure for creating a device link color profile according to the first embodiment.
FIG. 22 is a coordinate diagram showing a target value T ′ in the coordinates of the C and M color systems in the first embodiment.
FIG. 23 is a coordinate diagram showing a target value T in coordinates of a combination of C and M colors in the first embodiment.
FIG. 24 is a diagram illustrating the target value T ′ in the coordinates of the C and M color systems when the target value T ′ is out of the color reproduction range in the first embodiment.
FIG. 25 is a coordinate diagram showing the target value T ′ in the coordinates of the C and M color systems when the target value T ′ is outside the color reproduction range in the first embodiment. FIG. 9 is a coordinate diagram showing that the image is moved within the color reproduction range.
FIG. 26 is a diagram showing a target value T in coordinates of a combination of C and M colors when a target value T ′ outside the color reproduction range is moved into the color reproduction range in the first embodiment. It is.
FIG. 27 is a diagram showing correction contents of a device color profile.
FIG. 28 is a diagram showing correction contents of a device color profile.
FIG. 29 is a flowchart illustrating a procedure for creating a device link color profile according to the second embodiment.
FIG. 30 is a diagram showing correction contents of a device color profile.
FIG. 31 is a flowchart illustrating a procedure for creating a device link color profile according to the third embodiment.
FIG. 32 is a diagram showing C * max for each hab in the case of Kout = 153, in the coordinates of the color system of the value a * b * of the color system in the second embodiment.
[Explanation of symbols]
1 controller
10 Storage unit
12 Image data storage
13 LUT storage unit
11 Control unit
14 Color adjustment means
15 LUT creation means
2 Color printer for proofreading

Claims (11)

The first color image output device sets the color of the image output based on the image data as the target of color matching, and reproduces the target color with the second color image output device. The first color image output apparatus uses a combination of parameters of basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) in combination with parameters of the four basic colors on the output side. Using the color conversion table in which the combinations of the parameters of the four basic colors for outputting the color output by the second color image output device are associated, the parameters of the four basic colors shown in the image data are converted. A color adjustment method for converting and adjusting colors,
A first reference in which the first color image output device and the second color image output device are each associated with a combination of parameters of four basic colors and a color characteristic value indicating a color output by each combination. A combination of a table and four basic color parameters for outputting a color indicated by each color characteristic value to a plurality of color characteristic values based on the first reference table for the second color image output device Creating a second reference table that associates
The output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the first and second color image output devices. Creating a correction characteristic for correcting the parameter of K,
The color conversion table is created using the first reference table of the first color image output device and the second reference table of the second color image output device. The value of the color characteristic corresponding to the combination of the parameter of K in the first lookup table of the first color image output device where the parameter of K is 0 and the parameter of three colors of CMY is the first value of the second color image output device. Mapping the K parameter in the lookup table to 0 and the CMY three color parameters to color characteristic values corresponding to the maximum value combination;
Among the four basic color parameters on the input side of the created color conversion table, the combination of the three CMY parameters with the K parameter set to 0 is calculated based on the combination of the four basic colors on the output side. Are determined using the first reference table of the second color image output device, when the parameter of the color conversion table is set to 0, and the four color basics on the output side of the created color conversion table are obtained. Re-creating the color conversion table by replacing the combination of color parameters with the determined combination of three CMY parameters and the K parameter corrected using the correction characteristics. Method. The CMY three-color parameter combination obtained is based on the CMY three-parameter parameter combination with the K parameter set to 0, from the output-side four basic color combinations, to the second color image output device of the second color image output device. The color adjustment method according to claim 1, wherein the value of the color characteristic is obtained using the reference table of No. 1, and the value of the color characteristic is obtained using the case where the parameter of K of the first reference table is zero. The first color image output device sets the color of the image output based on the image data as the target of color matching, and reproduces the target color with the second color image output device. The first color image output apparatus uses a combination of parameters of basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) in combination with parameters of the four basic colors on the output side. Using the color conversion table in which the combinations of the parameters of the four basic colors for outputting the color output by the second color image output device are associated, the parameters of the four basic colors shown in the image data are converted. A color adjustment method for converting and adjusting colors,
A first reference in which the first color image output device and the second color image output device are each associated with a combination of parameters of four basic colors and a color characteristic value indicating a color output by each combination. A combination of a table and four basic color parameters for outputting a color indicated by each color characteristic value to a plurality of color characteristic values based on the first reference table for the second color image output device Creating a second reference table that associates
The output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the first and second color image output devices. Creating a correction characteristic for correcting the parameter of K,
The color conversion table is created using the first reference table of the first color image output device and the second reference table of the second color image output device. In the first lookup table of the first color image output device, the values of the color characteristics corresponding to the combinations of the maximum values of the CMY three colors in the first reference table are used as the values of the CMY three colors as the values obtained by correcting the K parameters with the correction characteristics. Mapping the combination having the maximum value to the value of the color characteristic obtained from the first reference table of the second color image output device;
For the combination of the parameters of the four basic colors on the input side of the created color conversion table, the parameter of K is corrected using the correction characteristics, and the four colors of the input side in the created color conversion table are corrected. K parameter obtained by performing the correction using the first reference table of the second color image output apparatus from the combination of the four basic color parameters on the output side corresponding to the combination of the basic color parameters And the combination of the four basic color parameters on the output side of the created color conversion table are converted to the combination of the determined three CMY parameters and the corrected K parameter. Replacing the color conversion table with a new color conversion table. The first color image output device sets the color of the image output based on the image data as the target of color matching, and reproduces the target color with the second color image output device. The first color image output apparatus uses a combination of parameters of basic colors (C (cyan), M (magenta), Y (yellow), and K (black)) in combination with parameters of the four basic colors on the output side. Using the color conversion table in which the combinations of the parameters of the four basic colors for outputting the color output by the second color image output device are associated, the parameters of the four basic colors shown in the image data are converted. A color adjustment method for converting and adjusting colors,
A first reference in which the first color image output device and the second color image output device are each associated with a combination of parameters of four basic colors and a color characteristic value indicating a color output by each combination. A combination of a table and four basic color parameters for outputting a color indicated by each color characteristic value to a plurality of color characteristic values based on the first reference table for the second color image output device Creating a second reference table that associates
The output of K in the first color image output device is reproduced by the second color image output device using each of the first lookup tables of the first and second color image output devices. Creating a correction characteristic for correcting the parameter of K,
The color conversion table is created using the first reference table of the first color image output device and the second reference table of the second color image output device. In the first lookup table of the first color image output device, the values of the color characteristics corresponding to the combinations of the maximum values of the CMY three colors in the first reference table are used as the values of the CMY three colors as the values obtained by correcting the K parameters with the correction characteristics. Mapping the combination having the maximum value to the value of the color characteristic obtained from the first reference table of the second color image output device;
A combination of parameters of the four basic colors on the output side of the created color conversion table is converted by the first reference table of the second color image output device to obtain a value of a color characteristic, and the obtained value is obtained. Obtaining a saturation from the value of the color characteristic;
A combination of parameters of the four basic colors on the input side of the created color conversion table corresponding to a combination of the parameters of the four basic colors on the output side at which the calculated saturation is not more than a predetermined saturation. , The K parameter is corrected using the correction characteristics, and the four basic color parameters of the output side corresponding to the combination of the four basic color parameters of the input side in the created color conversion table. , A combination of three CMY parameters with the corrected K parameter is obtained using the first reference table of the second color image output apparatus, and the output of the created color conversion table The combination of the parameters of the four basic colors on the side is determined by the combination of the parameters of the three CMY colors obtained above and the parameter of the corrected K. Color adjustment method characterized by comprising the steps of recreating the color conversion table by replacing data, the. The combination of the calculated three CMY color parameters is determined by using the first reference table of the second color image output device from the combination of the four basic color parameters on the output side, 5. The color adjustment method according to claim 3, wherein a parameter of K of the first reference table is obtained from the value of the color characteristic using a case of the corrected parameter. Further, the parameters of the four basic colors on the input side of the re-created color conversion table are C = M = Y = 0, and the parameters of the four basic colors on the output side corresponding to the combination in which K is not zero. The C, M, and Y parameters of the combination are changed to the four colors on the output side corresponding to the combination of C = M = Y = K = 0 when the parameters of the four basic colors on the input side of the recreated color conversion table are set. 6. The color adjustment method according to claim 3, wherein the C, M, and Y parameters of the combination of the basic color parameters are replaced with C, M, and Y parameters. Further, C, M, and Y of the four basic color parameters on the input side of the recreated color conversion table correspond to the combinations of the maximum values of the four basic color parameters C and M of the output side. 7. The color adjustment method according to claim 1, wherein the M and Y parameters are set to maximum values. The correction characteristic is obtained by using each of the first reference tables of the first color image output device and the second color image output device to determine the first reference table of the first color image output device. The color adjustment according to any one of claims 1 to 7, wherein the brightness obtained from the value of the color characteristic for the maximum value of the K parameter to 0 is created so as to be reproduced by the second color image output device. Method. 9. The correction characteristic according to claim 8, wherein the K parameter of the second color image output device is set to the maximum value when the K parameter of the first color image output device is the maximum value. Color adjustment method. A program for causing a computer to execute the color adjustment method according to claim 1. A recording medium on which the program according to claim 10 is recorded so as to be readable by the computer.

Images