JP2015070569A - Processor, processing method, and computer program for acquiring color values - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase in the number of patches printed for acquiring color values indicating a plurality of colors to be printed.SOLUTION: A processor is provided with an estimation unit for estimating the luminosity of a virtual patch using measurement values of the luminosity of a plurality of first mixed color patches; measurement values of the luminosity of a plurality of first single color patches; a measurement value of the luminosity of a specific first mixed color patch printed using N kinds of color materials in a same quantity of β; and a measurement value of the luminosity of a specific first single color patch printed using one kind of a color material in the amount of β among the plurality of single color patches. Each of the plurality of first mixed color patches is printed using the N kinds of color materials in a same quantity, and each of the plurality of first single color patches is printed using one of the N kinds of color materials. The virtual patch is a patch to be printed by using (N-1) kinds of color materials among the N kinds in a same quantity of α, and the rest of one kind among the N kinds of materials in the quantity of β.

Description

  The present invention relates to a technique for acquiring a plurality of color values indicating a plurality of colors printed using a plurality of types of color materials.

  A plurality of color values indicating a plurality of colors printed using a plurality of types of color materials (for example, a color value of a CIELAB color system, which is a device independent color system) is acquired. For example, these color values are converted from image data of a specific color system (for example, RGB color system) to image data of a color system (for example, CMYK color system) corresponding to a plurality of types of color materials. It is used to create a color conversion table for

  For example, in Patent Document 1, these color values are acquired by, for example, measuring a plurality of patches printed using a plurality of types of color materials. Then, a plurality of patches to be additionally printed are determined based on the colorimetric results of the plurality of printed patches. Then, the color value is further acquired by measuring the plurality of additionally printed patches.

JP 2009-164835 A JP 2005-184144 A JP 2005-94160 A

  However, in the above technique, for example, when it is difficult to predict in advance a patch from which a color value is to be acquired, there is a possibility that the number of times the patch is printed increases in order to acquire a necessary color value.

  It is an object of the present invention to suppress an increase in the number of times a patch is printed in order to acquire color values indicating a plurality of colors printed using a plurality of types of color materials.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples.

[Application Example 1] A processing apparatus for acquiring color values indicating a plurality of colors printed using N kinds (N is a natural number of 3 or more) of color materials, and a plurality of first devices having different densities. An acquisition unit that acquires a lightness measurement value of one mixed color patch and a lightness measurement value of a plurality of first single color patches having different densities, each of the plurality of first color mixing patches being N The types of color materials are printed using equal amounts, and each of the plurality of first single color patches is printed using one type of color materials of the N types of color materials. A lightness measurement value of a specific first color patch printed using equal amounts β of the N kinds of color materials among the plurality of first color patches, and the plurality of first color patches. Among the single-color patches, a specific first single-color patch printed using the one type of color material with the amount β. An estimation unit for estimating the brightness of the virtual patch using the measured value of the brightness of the h, wherein the virtual patch has (N-1) types of color materials of the N types equal to each α. A processing apparatus comprising: the estimation unit that is a patch that is used and the remaining one of the N types of color materials is to be printed using the amount β.

  According to the above configuration, (N-1) types of color materials are used in an equal amount α, and the remaining one of the N types of color materials is used in an amount β to determine the brightness of a color to be printed. Color patches can be estimated without actually printing. As a result, it is possible to suppress an increase in the number of times the patch is printed in order to obtain a necessary color value.

Application Example 2 A processing apparatus for obtaining color values indicating a plurality of colors printed using N types (N is a natural number of 3 or more) of color materials, and a plurality of first devices having different densities. An acquisition unit that acquires a lightness measurement value of one color mixture patch and a lightness measurement value of a plurality of second color mixture patches having different densities from each other, wherein each of the plurality of first color mixture patches includes: N types of color materials are printed using equal amounts, and each of the plurality of second color mixing patches uses equal amounts of (N-1) types of color materials among the N types of color materials. The measured value of the brightness of a specific first color mixture patch printed using the same amount α of the N kinds of color materials among the plurality of first color mixture patches. And among the plurality of second mixed color patches, the (N-1) kinds of color materials are used in an equal amount α. An estimation unit for estimating the lightness of the virtual patch using the lightness measurement value of the specific second mixed color patch printed and printed, wherein the virtual patch is the (N-1) types of color materials Is used for each of the equal amounts α, and the estimation unit is a patch to be printed with the remaining one of the N types of color materials using the amount β.

  According to the above configuration, (N-1) types of color materials are used in an equal amount α, and the remaining one of the N types of color materials is used in an amount β to determine the brightness of a color to be printed. Color patches can be estimated without actually printing. As a result, it is possible to suppress an increase in the number of times the patch is printed in order to obtain a necessary color value.

Application Example 3 In the processing apparatus according to Application Example 1 or Application Example 2, the N color materials include cyan, magenta, yellow, and black color materials, and the (N− 1) The processing apparatus, wherein the type of color material includes cyan, magenta, and yellow color materials, and the one type of color material of the virtual patch includes a black color material.
According to this configuration, the color color printed using cyan, magenta, and yellow color materials in equal amounts α and the black color material in amounts β is used to actually print a patch of that color. And can be estimated.

Application Example 4 In the processing apparatus according to Application Example 3, the acquisition unit further measures the lightness of a plurality of first single-color patches printed using the black color material and having different densities. The value is acquired, and the measured value of the brightness of a plurality of second single-color patches that are printed using one of the (N-1) types of color materials and have different densities is used as the value ( N-1) Obtained for each of the types of color materials, and the processing apparatus further determines whether or not the first color mixture patch having a specific density is a patch that exceeds a color material usage amount limit value. And when the first mixed color patch having the specific density is a patch that exceeds the use amount limit value, the first single-color patch and the first color patch and the determination unit so that the use amount limit value is not exceeded. Using the lightness measurement of the second single color patch, The amount of the coloring material of virtual patches alpha, and a determination unit for determining at least one value of beta, the estimation unit estimates the determined measured value of the brightness of the virtual patch processing apparatus.
The patches determined using the lightness measurement values of the first and second monochrome patches are printed only after printing and measurement of the first and second monochrome patches when actually printed. Can not. According to this configuration, the lightness of the virtual patch determined using the lightness measurement values of the first single color patch and the second single color patch can be added after the printing and measurement of the first single color patch and the second single color patch. Estimation can be made without printing a patch. Therefore, it is possible to effectively suppress an increase in the number of times the patch is printed.

Application Example 5 In the processing apparatus according to Application Example 4, in the case where the determination unit is a patch in which the first color mixture patch having the specific density does not exceed the use amount limit value. A processing device that does not determine the virtual patch.
According to this configuration, since the brightness of a virtual patch that does not need to be estimated is not estimated, an increase in processing time can be suppressed.

[Application Example 6] The processing apparatus according to Application Example 4 or Application Example 5, wherein the acquisition unit further includes:
The measurement values of the specific color component of the plurality of first single color patches are acquired, and the measurement values of the specific color component of the plurality of second single color patches are obtained for each of the (N-1) types of color materials. The specific color component is a color component related to at least one of hue and saturation, and the estimation unit further calculates a value of the specific color component of the virtual patch of a specific first single color patch. A process of estimating using the measured value of the specific color component and the measured value of the specific color component of (N-1) specific second single color patches of the (N-1) types of color materials apparatus.
According to this configuration, in addition to the brightness of the virtual patch, the value of a specific color component of the virtual patch can be estimated.

[Application Example 7] The processing apparatus according to any one of Application Example 1 to Application Example 6, and further using the estimated brightness of the virtual patch, the first color data of the first color system And a generation unit that generates a table that associates the second color data of the second color system having a plurality of components corresponding to the plurality of types of color materials, and the first color data includes , A target lightness is associated, and the first color data is associated with the second color data representing a color having the target lightness.
According to this configuration, in order to generate a table that associates the first color data of the first color system and the second color data of the second color system, the number of times the patch is printed is suppressed. can do.

Application Example 8 A processing apparatus for acquiring color values indicating a plurality of colors printed using N types (N is a natural number of 3 or more) of color materials, and using one type of color material An acquisition unit that acquires, for each of the N types of color materials, a measurement value of a specific color component of a plurality of single-color patches that are printed and have different densities, and the specific color component includes hue and saturation The value of the specific color component of the virtual patch is estimated using the measurement value of the specific color component of each specific single color patch of the N types of color materials, which is a color component related to at least one of In this estimation unit, the virtual patch uses (N-1) types of color materials of the N types in equal amounts α, and the remaining one of the N types of color materials is an amount. the estimator, which is a patch to be printed using β , Processing equipment.

  According to the above configuration, the value of the specific color component of the color printed using two or more first color materials and the second color material in an amount different from the two or more first color materials, Color patches can be estimated without actually printing. As a result, it is possible to suppress an increase in the number of times the patch is printed in order to obtain a necessary color value.

[Application Example 9] The processing apparatus according to Application Example 8, wherein the value of the specific color component of the estimated virtual patch is the specific color component of each specific single color patch of the N types of color materials Or a sum of interpolated values calculated for each of the N color materials based on the measured values of the specific color component of the specific single color patch.
According to this configuration, it is possible to easily estimate an appropriate value of the specific color component of the virtual patch.

  The present invention can be realized in various forms, for example, a color conversion table creation device, a method for obtaining color values, a color conversion table creation method, and these devices or methods. The present invention can be realized in the form of a computer program for recording, a recording medium on which the computer program is recorded, and the like.

It is a block diagram which shows the structure of the printer 200 as a table preparation apparatus. It is a flowchart of a color conversion table generation process. It is a figure which shows an example of the patch sheet | seat 10 showing a patch image. It is a figure which shows an example of the table in which the measured value of each patch is recorded. An example of the interpolation value table is generated. It is a figure explaining the production | generation of a calibration table. It is a figure which shows an example of a calibration table with a graph. It is a flowchart of the estimation process of Lab value. It is a figure which shows the calculation formula of the total usage, and the calculation formula of the virtual CMY usage. It is a figure explaining estimation of L value of a virtual patch of the 1st example. It is a figure explaining estimation of a value and b value of virtual patch ((alpha), (beta)). It is a flowchart of the generation process of a partial color conversion table. It is a figure explaining the production | generation of a partial color conversion table. It is a figure explaining the hue line in RGB color space. It is a figure explaining estimation of the L value of the virtual patch of 2nd Example. It is a figure explaining estimation of the L value of the virtual patch of 3rd Example.

A. First embodiment:
A-1. Multi-function machine configuration:
Next, embodiments of the present invention will be described based on examples. FIG. 1 is a block diagram showing a configuration of a printer 200 as a table creation device in the first embodiment.

  The printer 200 includes a CPU 210, a volatile storage device 220 such as a RAM, a non-volatile storage device 230 such as a hard disk drive and a flash memory, a printing mechanism 240 as a print execution unit, and an operation unit 260 such as a touch panel and buttons. A display unit 270 including a liquid crystal display panel superimposed on the touch panel, a communication unit 280 as an interface for performing data communication with an external device such as a personal computer or a portable terminal, and a colorimeter 290. ing.

  The printing mechanism 240 includes three types of chromatic inks (also referred to as C ink, M ink, and Y ink) of cyan (C), magenta (M), and yellow (Y), and achromatic ink (K) of black (K). This is an ink jet printer that prints an image using four types of ink (color materials). The printing mechanism 240 includes a print head, a main scanning mechanism, and a transport mechanism (not shown). The transport mechanism transports the paper with the power of the transport motor. The main scanning mechanism includes a carriage on which the print head is mounted, and reciprocates (main scans) the carriage on which the print head is mounted in the main scanning direction by the power of the main scanning motor. The print head is provided with a plurality of nozzles for discharging ink (not shown).

  The colorimeter 290 is, for example, a spectroscopic colorimeter, and includes a light source, a lens, and an optical sensor (not shown). The colorimeter 290 is mounted on the carriage, and can measure the color at an arbitrary position on the paper transported by the transport mechanism. Specifically, the colorimeter 290 irradiates light from a light source to a measurement position on a sheet, disperses the reflected light with a lens, and measures the amount of light in each wavelength range that has been dispersed using an optical sensor. The measurement results of the colorimeter 290 are processed by the CPU 210 and converted into color values (also referred to as Lab values) in the CIELAB color space and optical densities (also referred to as OD values).

  For example, the volatile storage device 220 provides a buffer area 221 that temporarily stores various intermediate data generated when the CPU 210 performs processing.

  The nonvolatile storage device 230 stores a program 231 and patch data 232. The program 231 and the patch data 232 are provided in a form downloaded from a server, for example. Further, the program 231 and the patch data 232 may be provided in a form stored in a DVD-ROM, for example.

  The CPU 210 functions as a control device for the printer 200 by executing the program 231. Specifically, the CPU 210 executes a general control process as a printer that controls the printing mechanism 240 to execute printing, and a color conversion table generation process to be described later.

  The patch data 232 is image data representing a patch image used in a color conversion table generation process described later.

A-2. Printing process:
The printer 200 executes print processing based on a print instruction from the user. Specifically, the CPU 210 of the printer 200 receives image data in a predetermined format (for example, JPEG-compressed image data or image data described in a page description language) from an external device based on an instruction from the user. get. The CPU 210 performs rasterization processing, color conversion processing, calibration processing, and halftone processing on the acquired image data to generate dot data.

  The rasterization process is a process for converting acquired image data into RGB image data, for example. The RGB image data includes color data of an RGB color system (for example, sRGB color system) having gradation values (for example, 256 gradations) of three components of RGB for each pixel.

  The color conversion process is a process of converting RGB image data into CMYK image data using a color conversion table. The CMYK image data includes color data of the CMYK color system having four component gradation values (for example, 256 gradations) corresponding to four types of CMYK inks for each pixel. The color conversion table is, for example, a lookup table that associates a plurality of color data of the RGB color system with a plurality of color data of the CMYK color system.

  The calibration process is a process of correcting each component value so that the density of the color printed on the paper changes linearly with respect to the change in each component value of the pixel values (CMYK values) of the CMYK image data. is there. The calibration process is executed using a calibration table prepared for each of the four components of CMYK. The calibration table is a one-dimensional lookup table that associates component values (input values) before correction with component values (output values) after correction.

  Halftone processing is processing for converting CMYK image data into dot data indicating the dot formation state for each pixel. The dot formation state of each pixel is represented by, for example, two gradations of “no dot” and “with dot”, or four gradations of “no dot”, “small”, “medium”, and “large”. For the halftone process, a known process such as an error diffusion method or a dither method is used.

  The CPU 210 generates a print job including print data obtained by rearranging the dot data in the order used for printing and control data for controlling the printing mechanism 240. The CPU 210 controls the printing mechanism 240 according to the generated print job, and prints an image represented by the print data on a sheet.

A-3. Color conversion table generation processing:
In the color conversion table generation process, a color conversion table and a calibration table used in the printing process described above are generated. The color expressed by the ink may differ depending on various printing conditions, for example, the type of paper (glossy paper, plain paper, etc.). For this reason, the ideal color conversion table and calibration table may differ depending on the printing conditions. The printer 200 according to the present exemplary embodiment performs color conversion suitable for a sheet by executing a color conversion table generation process based on a user instruction when, for example, changing a sheet used for printing to a specific type of sheet. A table and a calibration table can be newly generated.

  FIG. 2 is a flowchart of the color conversion table generation process. In step S <b> 10, the CPU 210 creates a patch sheet 10 by printing a patch image including a plurality of patches on a specific type of paper. The patch image is printed using the patch data 232 (FIG. 1). The patch data 232 is, for example, CMYK image data representing a patch image or dot data.

  FIG. 3 is a diagram illustrating an example of the patch sheet 10 representing a patch image. The patch sheet 10 includes four types of single-color patch groups, that is, a cyan patch group 11, a magenta patch group 12, a yellow patch group 13, and a black patch group 14.

  Each of the plurality of patches included in one single color patch group is a single color patch printed using one kind of ink. For example, the cyan patch group 11 includes 100 patches having different C ink densities. FIG. 1 illustrates some patches CPa to CPd out of 100 single-color patches. In other words, 100 patches use different amounts of C ink per unit area. The amount of ink used per unit area is expressed using the ratio (%) of the number of dots formed to the number of positions where dots can be formed. In other words, the usage amount per unit area is represented by using the ratio (%) of the number of pixels to form dots to the total number of pixels of dot data representing a patch. Hereinafter, the amount of ink used per unit area is also simply referred to as ink usage. The ink usage of 100 patches of the cyan patch group 11 is a value in 1% increments from 1% to 100%.

  Similarly, each of the magenta patch group 12, the yellow patch group 13, and the black patch group 14 is printed using a corresponding type of ink (M ink, M ink, Y ink, K ink), and the amount of ink used. Contains 100 single color patches in 1% increments from 1% to 100%.

  The patch sheet 10 further includes a CMY patch group 15 and a CMYK patch group 16. The CMY patch group 15 includes 100 CMY mixed color patches that are printed using equal amounts of three types of CMY inks and have different densities. The CMYK patch group 16 includes 100 CMYK mixed-color patches that are printed using equal amounts of four types of CMYK inks and have different densities. The amount of ink used per one type of ink of 100 CMY color mixture patches is a value in increments of 1% from 1% to 100%. Similarly, the amount of ink used per one type of ink of 100 CMYK mixed color patches is a value in 1% increments from 1% to 100%. The CMY mixed color patch and the CMYK mixed color patch have colors close to an achromatic color, but are not completely achromatic colors and may have a slight saturation.

  The patch sheet 10 further includes three types of secondary color patch groups, that is, a red patch group 17, a green patch group 18, and a blue patch group 19. Each of the plurality of patches included in one secondary color patch group is a secondary color patch printed by using an equal amount of two types of CMY three types of ink. For example, the red patch group 17, the green patch group 18, and the blue patch group 19 are printed using two types of inks of magenta and yellow, yellow and cyan, and cyan and magenta, respectively, and have 100 different densities. Contains patches. The amount of ink used per one type of 100 patches included in each secondary color patch group is a value in 1% increments from 1% to 100%.

  In step S20, the CPU 210 calculates the colorimetric values of each patch in the patch sheet 10, that is, the measured values of each component value (L value, a value, b value) of Lab and the optical density (OD value). get. The L value indicates lightness, and the a value and b value indicate values related to hue and saturation. Specifically, the patch sheet 10 sufficiently dried by the user is set on a paper feed tray (not shown) of the printer 200. The CPU 210 controls the transport mechanism and the main scanning mechanism of the printing mechanism 240 to sequentially move the colorimeter 290 to the position of each patch, while using the colorimeter 290 to determine the L value of each patch, a Get the value, b value, and OD value.

  FIG. 4 is a diagram illustrating an example of a table in which measured values of each patch are recorded. In this table 20, 100 sets of measurement values (L value, a value, b value, OD value) of 100 patches of the cyan patch group 11 are recorded. In FIG. 4, the L value, a value, b value, and OD value of a cyan single color patch whose ink usage amount is M% (M is an integer of 0 to 100) are respectively represented by L_CM, a_CM, b_CM, D_CM, It is represented by The value of M = 0 (ink usage amount 0%) is a measured value (measured value of paper color) of the patch sheet 10 where no patch is printed. In step S20, such a table is generated for each of the nine patch groups 11-19.

  In subsequent step S30, CPU 210 determines a limit value for the ink amount. Specifically, the limit value for black ink (also referred to as K single color limit value IMX_K), the limit value for single color of chromatic ink (CMY ink) (also referred to as color single color limit value IMX_CL), and the CMY A limit value (referred to as CMY limit value IMX_CMY) for the total use amount of three types of ink and a limit value (also referred to as total limit value IMX_total) for the total use amount of the four types of CMYK inks are determined. The reference density (reference OD value) D_Kth of the black monochrome patch, the reference density D_Cth, D_Mth, D_Yth of the CMY monochrome patch, the reference density D_CMYth of the CMY mixed patch, the reference density D_CMYKth of the CMYK mixed patch, and RGB Next color patches D_Rth, D_Gth, and D_Bth are determined in advance. IMX

  The CPU 210 selects the patch with the minimum ink usage amount from among the 100 single-color patches of black having the OD value equal to or higher than the reference density D_Kth. The CPU 210 determines the ink usage amount of the selected patch as the K single color limit value IMX_K.

  The CPU 210 selects the patch with the minimum ink usage amount from among the 100 single-color patches of cyan among patches having an OD value equal to or higher than the reference density D_Cth. Similarly, a patch having the minimum ink use amount is selected from among the 100 single-color patches of magenta and yellow, among patches having an OD value equal to or higher than the reference densities D_Mth and D_Yth. The CPU 210 determines the average value of the ink usage of the three selected patches of cyan, magenta, and yellow as the color single color limit value IMX_CL. For example, in the example of FIG. 4, a patch with an OD value of D_C90 is selected, and the ink usage of the selected patch is 90%.

  The CPU 210 selects a patch with the minimum ink usage amount from patches having an OD value equal to or higher than the reference density D_CMYth from among 100 CMY mixed color patches. The CPU 210 determines the total value of the three CMY ink usage amounts of the selected patch as the CMY limit value IMX_CMY.

  The CPU 210 selects a patch with the minimum ink usage amount from patches having an OD value equal to or higher than the reference density D_CMYKth from among 100 CMYK mixed color patches. The CPU 210 determines the total value of the four types of CMYK ink usage of the selected patch as the total limit value. Here, for the calculation of the total limit value, a value (color conversion value) obtained by multiplying the black ink usage amount by (color single color limit value IMX_CL / K single color limit value IMX_K) is used as a conversion coefficient. The conversion factor is multiplied because chromatic ink (C, M, Y) is more likely to bleed than black ink. That is, by multiplying by the conversion factor, the total limit value IMX_total when using chromatic color inks that tend to bleed is calculated in consideration of the degree of bleed between chromatic ink (C, M, Y) and black ink. Is done.

  The values of the K single color limit value IMX_K, the color single color limit value IMX_CL, the CMY limit value IMX_CMY, and the total limit value IMX_total are, for example, about 90%, about 80%, about 100%, and about 120%.

  Furthermore, the CPU 210 sets ink amount limit values (also referred to as G limit value IMX_R, G limit value IMX_G, and B limit value IMX_B) for each secondary color of red (R), green (G), and blue (B). Decide each. Specifically, as with the other limit values, two types of ink use are made of patches with the smallest ink use amount among secondary color patches having OD values of RGB reference densities D_Rth, D_Gth, and D_Bth. The total amount is set as a limit value for each of the RGB ink amounts.

  In step S40, the CPU 210 calculates an interpolated value of the measured value in consideration of the ink usage limit value. In FIG. 5, an example of the interpolation value table is generated. The CPU 210 sets the minimum value of the ink use amount to “0”, sets the maximum value of the ink use amount as the limit value calculated in step S30, and sets the minimum value to the maximum value to a predetermined number (for example, 16). Divide. Then, the L value, a value, b value, and OD value for a plurality (for example, 17) of ink usage at equal intervals from the minimum value to the maximum value are calculated using the measured values (FIG. 4). For example, in the example of FIG. 5B, an example of the cyan interpolation value table 21 when the color single color limit value IMX_CL is 90% is shown. In this example, the L value, the a value, the b value, and the OD value are calculated for each of the 17 ink usage amounts in increments of 5.625% from 0% to 90%. For example, the L value L_Ca15 corresponding to the ink usage amount of 84.375% uses the measured value L_C84 of the 84% cyan single color patch and the measured value L_C85 of the 85% cyan single color patch. Calculated by linear interpolation.

  Similarly, interpolation values for the magenta (M), yellow (Y), and black (K) single color patches, the CMY mixed color patch, and the red (R), green (G), and blue (B) secondary color patches, respectively. A table is generated.

  In step S50, the CPU 210 generates a calibration table. FIG. 6 is a diagram illustrating generation of a calibration table.

  Optical density target values (OD target values) for four component values (C value, Y value, M value, K value (for example, 256 gradations)) corresponding to four types of CMYK inks are determined in advance. Yes. FIG. 6A shows the target value of the optical density with respect to the cyan component value (C value). The OD target value Dtar_C0 of the minimum C value (0) is the optical density of the paper. The OD target value Dtar_C255 of the maximum C value (255) is the reference concentration D_Cth described above. The OD target value between the minimum value and the maximum value of the C value changes linearly with respect to the change of the C value. In other words, the graph with the C value on the horizontal axis and the OD target value on the vertical axis is a straight line connecting the OD target value Dtar_C0 having the minimum value “0” and the OD target value Dtar_C255 having the maximum value “255”. (FIG. 6A).

  The CPU 210 determines the OD for each of a plurality (for example, 17) of representative values (for example, 0, 16, 32, 64,..., 240, 255) at equal intervals from the minimum value to the maximum value of the C value. Get the target value. Then, with reference to the interpolation value table 21 of FIG. 5, the ink usage corresponding to the acquired OD target value is calculated. For example, a specific ink usage amount V_C128 is calculated as the ink usage amount corresponding to the OD target value Dtar_C128 of the C value “128”. The CPU 210 multiplies the ink usage amount corresponding to the OD target value of the representative value of the C value by the maximum value “255” of the C value to calculate a calibration correction value (C ′ value) of the representative value of the C value. . For example, (255 × V_C128) is calculated as the C ′ value corresponding to the C value “128” (FIG. 6B). The C ′ value corresponding to the maximum C value “255” is represented by 255 × 90% (about 230) when the color single-color limit value IMX_CL is 90%. By calculating C ′ values corresponding to all representative values of the C values, a cyan component value calibration table is completed.

  FIG. 7 is a graph showing an example of the calibration table. The calibration table is a one-dimensional lookup table in which the C value is an input value and the C ′ value is an output value. The calibration table includes a plurality of input values and a plurality of usage amounts of corresponding color materials (in this embodiment, usage amounts converted to 256 gradations) with respect to changes in the input values. It can be said that this is a table for associating so that the density of the color to be printed changes linearly. In the example of FIG. 7, the graph in which the values of the calibration table are plotted is a downwardly convex curve. The calibration table is generated for each of the four types of CMYK inks. In this embodiment, a common table may be used as the calibration table for the three components CMY.

  In subsequent step S60, CPU 210 executes Lab value estimation processing. Among the 100 CMYK mixed color patches, the CPU 210 prints a virtual CMYK mixed color patch (also referred to as a virtual patch) corresponding to the CMYK mixed color patch for a patch printed using an ink amount exceeding the total limit value IMX_total described above. ) To estimate the Lab value of the virtual patch. The Lab value estimated for the virtual patch is used to generate the color conversion table (partial color conversion table) of the achromatic color axis in step S70.

FIG. 8 is a flowchart of Lab value estimation processing.
In step S100, the CPU 210 determines a plurality of patches to be processed from the 100 CMYK mixed color patches in the CMYK patch group 16 (FIG. 3). In this embodiment, the CPU 210 treats all 100 CMYK mixed color patches. Instead of this, the plurality of patches to be processed may be only a specific number of patches necessary for generating an achromatic color axis color conversion table to be described later.

  In step S105, the CPU 210 selects one patch as a target patch from among a plurality of CMYK mixed color patches to be processed. In step S110, the CPU 210 calculates the total ink usage IV_total of the patch of interest.

  FIG. 9 is a diagram illustrating a calculation formula for the total usage amount IV_total and a calculation formula for the virtual CMY usage amount IV_CLvir. The total usage amount IV_total is calculated using Expression (1) in FIG. IV_CL in equation (1) is the amount of cyan, magenta, and yellow ink (CMY ink) used per one type of ink. If the target patch is a 10% CMYK mixed color patch, IV_CL = 10 It is. IV_Ka is a color conversion value of the amount of black ink (K ink) used, and is expressed using equation (2) in FIG.

  IV_K in Expression (2) is the usage amount of K ink, and IV_K = 10 when the target patch is a 10% CMYK mixed color patch. As described above, the K ink use amount IV_Ka is calculated by multiplying the K ink use amount IV_K by the conversion coefficient (color single color limit value IMX_CL / K single color limit value IMX_K) (formula (2) )).

  In step S115, the CPU 210 determines whether or not the calculated total ink usage IV_total of the target patch exceeds the total limit value IMX_total (for example, 120%). When the total amount of ink IV_total used in the patch of interest does not exceed the total limit value IMX_total (step S115: NO), the CPU 210 sets the measured value of the Lab value of the patch of interest as the Lab value of the patch of interest. That is, in this case, the CPU 210 does not determine a virtual CMYK mixed color patch (virtual patch) described later. Therefore, in this case, the Lab value of the virtual patch is not estimated.

  If the total usage IV_total of the ink of the patch of interest exceeds the total limit value IMX_total (step S115: YES), the CPU 210 does not change the usage of the K ink of the patch of interest and uses the CMY ink. Is changed so that the total limit value IMX_total is not exceeded. In other words, the usage amount IV_CLvir per one type of virtual CMY ink is calculated.

  The virtual CMY usage amount IV_CLvir is calculated using Equation (3) in FIG. Re in Equation (3) is a reduction rate that should reduce the amount of CMY ink used so that the total limit value IMX_total is satisfied on the assumption that the amount of K ink used is not changed. The decrease rate Re is expressed using Expression (4).

  The denominator (IV_total-IV_Ka) on the right side of Equation (4) is the total value of the amount of CMY ink used for the patch of interest. The numerator (IMX_total-IV_Ka) on the right side of Equation (4) is the upper limit of the total amount of CMY inks that can be used within a range not exceeding the total limit value IMX_total.

  An example of calculation is shown by taking as an example a case where a CMYK mixed color patch with 50% ink usage is the target patch. The values of the K single color limit value IMX_K, the color single color limit value IMX_CL, and the total limit value IMX_total are 90%, 80%, and 120%. The color conversion value IV_Ka (50 × 80/90) of the usage amount of the K ink in Expression (2) is about 44.4. Therefore, the total usage amount IV_total (3 × 50 + 44.4) is about 194.4, which exceeds the total limit value IMX_total = 120%. In this case, the reduction rate Re {(120-44.4) / (194.4-44.4)} is about 0.504. Therefore, the virtual CMY usage IV_CLvir {0.504 × (194.4-44.4)} is approximately 25.2%.

  The ink usage amount per color of the target patch (CMYK mixed color patch) is “β”, and the virtual CMY usage amount IV_CLvir calculated using the equation (3) is “α”. In this case, the virtual patch determined in this step is a patch to be printed using three types of CMY inks of equal amounts α and K ink amounts β. Such a virtual patch is called a virtual patch (α, β). “Β” can also be said to be the usage amount of the K ink of the virtual patch (α, β). A virtual patch corresponding to a CMYK mixed color patch with an ink usage amount of 50% is a virtual patch (25.2, 50).

  In step S130, the CPU 210 estimates the L value L_vir (α, β) of the virtual patch (α, β). FIG. 10 is a diagram illustrating the estimation of the L value L_vir (α, β) of the virtual patch (α, β) according to the first embodiment. The L value L_vir (α, β) is calculated using the equation (5) in FIG. L_K (β) is a measured value of the L value of the K single-color patch with the usage amount β. L_CMYK (β) is a measured value of the L value of the CMYK mixed color patch with the usage amount β.

  As shown in FIG. 10 (B), the absolute value of (L_CMYK (β) −L_K (β)) is the L when three types of CMY inks are added to the K single color patch of the usage amount β by the amount β. It represents the amount of change in value. Therefore, (L_CMYK (β) −L_K (β)) × (α / β) is the amount of change in the L value when three types of CMY inks are added to the K single color patch of the usage amount β by the amount α. It is thought that it represents. Since the virtual patch (α, β) is considered to be a patch obtained by adding three types of CMY inks by the amount α to the K single color patch of the usage amount β, the equation (5) in FIG. 10A is used. Thus, the L value (lightness) of the virtual patch (α, β) can be estimated.

  In step S135, the CPU 210 calculates the estimated value a_vir (α, β) of the a value of the virtual patch (α, β) and the estimated value b_vir (α, β) of the b value. FIG. 11 is a diagram illustrating estimation of the a value a_vir (α, β) and the b value b_vir (α, β) of the virtual patch (α, β). The a value a_vir (α, β) is calculated using equation (6) in FIG. a_K (β) is a measured value of the a value of the K single-color patch with the usage amount β. a_C (α), a_M (α), and a_Y (α) are measured values of the a value of each single-color patch of CMY of the usage amount α. If there is no single-color patch with a usage amount α, the single-color patch with the largest usage amount among the single-color patches with a usage amount smaller than the usage amount α and the smallest one of the single-color patches with a usage amount larger than the usage amount α. It is calculated by linear interpolation using a single color patch. As can be seen from FIG. 11A, the sum of the measurement values a_C (α), a_M (α), a_Y (α), and a_K (β) for each ink is used as the estimated value a_vir (α, β). Calculated. As a result, it is possible to easily calculate an estimated value a_vir (α, β) of an appropriate a value. Similarly, b value b_vir (α, β) is calculated using equation (7) in FIG.

  In step S140, the CPU 210 calculates the L value L_vir (α, β), the a value a_vir (α, β), and the b value b_vir (α, β) calculated for the virtual patch (α, β), respectively. Associate with virtual patches (α, β).

  In step S145, the CPU 210 determines whether or not all CMYK mixed color patches to be processed have been processed as the target patch. If there is an unprocessed patch (step S145: NO), the CPU 210 returns to step S105, selects the unprocessed patch as a target pixel, and repeats the above-described processing. If all the patches have been processed (step S145: YES), the process is terminated.

  In step S70, the CPU 210 generates an achromatic color axis color conversion table (also referred to as a partial color conversion table) in the RGB color system. FIG. 12 is a flowchart of a partial color conversion table generation process. FIG. 13 is a diagram illustrating generation of a partial color conversion table.

  In step S200, the CPU 210 acquires the target value L_tar of the L value of the representative value (also referred to as representative color data) on the achromatic color axis in the RGB color system. The representative values on the achromatic axis are, for example, a plurality of (for example, 17) representative values (for example, 17 values) from the black value K (0, 0, 0) of the RGB color system to the white value (255, 255, 255) ( For example, the RGB component values are 0, 16, 32, 64,..., 240, 255). A table in which the target value L_tar of the L value is associated with these representative values is incorporated in the program 231 in advance. As shown in FIG. 13A, for example, a graph in which the representative value on the achromatic color axis is taken and the target value L_tar of the L value is taken on the vertical axis is convex downward from the white value W toward the black value K. The curve decreases monotonously.

  In step S210, the CPU 210 determines the usage amount of K ink to be associated with the representative value on the achromatic color axis with reference to the target value of the L value L_tar. Specifically, the amount of K ink used for associating a plurality of representative values from the position Tth (FIG. 13) on the achromatic color axis where the target value of the L value L_tar becomes the reference value Lth to the black value is determined. Is done. First, the CPU 210 does not drop below the target value L_tar of the representative value to which the K ink use amount should be associated, and considers the decrease in the L value due to the CMY ink use amount to be determined later. Determine the amount of use. Further, in order to prevent the amount of ink used for association from exceeding the total limit value IMX_total, for example, the representative value close to the black value is associated with a larger amount of K ink used so that the amount of CMY ink used is reduced. It is done. At this time, in the region RB (FIG. 13B) where the amount of K ink used is less than the amount of CMY ink used, the measured value of the L value of the K single color ink (FIG. 4) and the colorimetric value are used. Reference is made to the interpolated value (FIG. 5). Further, in the region RC on the black side from the position where the assumed usage amount of CMY ink and the usage amount of K ink are substantially equal (FIG. 13B), the measured value of the L value of the CMYK mixed color patch or in step S60. The L value of the estimated virtual patch is used. As a result, as shown in FIG. 13B, a K ink usage amount curve with respect to the achromatic color axis is set.

  In step S220, the CPU 210 determines the amount of CMY ink used to be associated with each representative value on the achromatic color axis. For example, in the region RA (FIG. 13B) where the usage amount of K ink is not associated, an approximate value of the associated CMY ink usage amount is determined so as to achieve the target L value. In this area RA, the measurement value (FIG. 4) of the L value of the CMY mixed color patch and the interpolation value (FIG. 5) based on the measurement value are used.

  In the region RB and the region RC, the L value L_k (measured value or interpolated value) of the K single color patch of the K ink usage amount V_K associated with the representative value on the achromatic color axis and the L value target value L_tar Using the difference (L_k-L_tar), the approximate value V_CMY of the amount of CMY ink used is calculated by the following equation (8).

  V_CMY = V_K × {(L_K−L_tar) / (L_K−L_CMYK)} (8)

  Here, L_CMYK is an L value of the CMYK mixed color patch having the same usage amount as the usage amount V_K of the K ink associated with the representative value on the achromatic color axis.

  When the approximate value of the CMY usage amount is determined, the CPU 210 determines the CMY usage amounts V_C, V_M, and V_Y to be associated with the representative values on the achromatic color axis by correcting the approximate value. That is, the saturation of the color obtained by mixing the inks with the ink usage amounts V_C, V_M, V_Y, and V_K to be matched is set to 0, that is, the a value and the b value are set for each target representative value. The approximate value is adjusted for each ink so that the target a value and the target b value are obtained. These adjustments are performed by adjusting the a and b values (measured value, interpolated value, and estimated value) of the CMY mixed color patch, the CMYK mixed color patch, the virtual patch, and the a and b values (measured value and interpolated value) of the CMY single color patch, respectively. Value) and are executed.

For example, the target a value of the minimum representative value “0” is the a value of the color of the paper that is not printed. The target a value of the maximum representative value “255” is the a value of the color printed on the paper using only the K ink having the maximum ink usage amount within a range not exceeding the K single color limit value IMX.
The target a value of another representative value is calculated by linear interpolation using the target a value of the minimum representative value “0” and the maximum representative value “255”. The same applies to the target b value. When the target a value and the target b value of the minimum representative value “0” are “0” and the target a value and the target b value of the maximum representative value “255” are “0”. The target a value and the target b value of all the representative values are “0”.

  The partial color conversion table of the achromatic color axis is generated by the processing described above.

  The CMYK ink usage (unit:%) associated with each of the plurality of representative values of the achromatic color axis is represented by 256 gradation component values (C ′ value, M ′ value, Y ′ value, K ′). Value), and further using the calibration table, the C value, M value, Y value, and K value before calibration correction are converted to complete the achromatic color partial color conversion table. FIG. 13B shows an example of an achromatic color axis partial color conversion table. It can be seen that the amounts of CMY ink used are substantially equal, but do not completely match.

  In step S80, the CPU 210 determines an ink usage amount that is associated with a representative value on a hue line passing on the surface of the RGB color space. That is, the CPU 210 generates a partial color conversion table on the hue line.

  FIG. 14 is a diagram illustrating a hue line in the RGB color space. The RGB color system color space SCP shown in FIG. 14 includes a black point (K point), a white point (W point), three primary color points, three secondary color points, and six. And an intermediate color point.

  The primary color points are the three points corresponding to the three chromatic inks (C, M, Y), the C point, the M point, and the Y point. In other words, the primary color point is a point on the color space SCP in which two of the RGB color components have the maximum value (255 in the present embodiment) and the remaining one has the minimum value (0 in the present embodiment). is there. The primary hue line is a line connecting the W point and the primary color point in the color space SCP and connecting the primary color point and the black point. FIG. 14 shows three primary hue lines, that is, a C hue line CLC passing through the point C, an M hue line CLM passing through the M point, and a Y hue line CLY passing through the Y point.

  The secondary color points are the three points corresponding to the secondary colors R, G, and B, the R point, the G point, and the B point. In other words, the secondary color point is a point on the color space SCP in which one of the RGB color components has the maximum value and the remaining two have the minimum value. The secondary hue line is a line connecting the W point and the secondary color point in the RGB color space SCP and connecting the secondary color point and the black point. FIG. 14 shows three secondary hue lines, that is, an R hue line CLR passing through the R point, a G hue line CLG passing through the G point, and a B hue line CLB passing through the B point.

  The intermediate color points are midpoints of six sides connecting the primary color point and the secondary color point among the 12 sides of the rectangular parallelepiped that is the color gamut of the color space SCP. That is, the intermediate color points are the RY point that is the midpoint of the RY side, the YG point that is the midpoint of the YG side, the GC point that is the midpoint of the GC side, and the BC side. There are six points: a BC point which is the midpoint, an MB point which is the midpoint of the MB side, and an MR point which is the midpoint of the MR side (FIG. 14)). In other words, the intermediate color point is a point on the color space SCP in which one of the RGB color components has the maximum value, one has the minimum value, and the other one has the intermediate value (128 in this embodiment). . FIG. 14 illustrates an MB hue line CLMB passing through the MB point and a BC hue line CLBD passing through the BC point, among the six intermediate hue lines. The other four intermediate hue lines, that is, the RY hue line passing through the RY point, the YG hue line passing through the YG point, the GC hue line passing through the GC point, and the MR hue line passing through the MR point make the figure complicated. The illustration is omitted for the sake of avoidance.

  The CPU 210 uses a plurality of ink value limit values determined in step S30 and a plurality of interpolation value tables generated in step S40 to generate a plurality of representative values (for example, a rectangular parallelepiped) on each hue line. 4 types of ink use amounts of CMYK to be associated with (17 representative values per side of the RGB color space). At this time, the ink amount is determined so that the limit value of the ink amount is not exceeded and the range of colors that can be expressed (for example, the color gamut size in the CIELAB color space) is as large as possible. The CMYK ink usage (unit:%) associated with the representative value of each hue line is converted into 256 gradation component values (C ′ value, M ′ value, Y ′ value, K ′ value). Further, the partial color conversion table for each hue line is completed by converting the C value, M value, Y value, and K value before calibration correction using the calibration table.

  In step S80, the CPU 210 uses the achromatic color axis GL (FIG. 14) and the partial color conversion table of the 12 hue lines, and RGB color system color data (RGB values) and CMYK color system color data. A color conversion table that associates (CMYK values) with each other is generated. That is, CMYK values associated with a predetermined number of representative values (grid values) in the RGB color space other than the achromatic color axis GL and the 12 hue lines are calculated by interpolation processing.

  A method for determining the ink amount of the CMYK values on these hue lines and other grid interpolation processing methods are executed using various known methods. For example, one known method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-33930.

  According to the first embodiment described above, the color conversion table can be generated without additionally printing a patch after the ink amount limit value is determined in step S30 of FIG. As a result, when the color conversion table is generated, the number of times the patch is printed can be reduced. Printing a patch necessitates a step of drying the patch sheet and a step of measuring the color of the patch in the patch sheet, which increases the work load for generating the color conversion table. In this embodiment, the work load for generating the color conversion table can be reduced by reducing the number of times the patch is printed.

  More specifically, in step S40, the interpolation value table 21 of FIG. 5 is generated using the limit values of the four types of ink, and in step S50, the calibration table is referred to the interpolation value table 21. Generated. In order to generate the calibration table, it is necessary to print a new patch group in which the ink use amount is changed in consideration of the ink limit value. In the present embodiment, no additional patches are printed to generate the calibration table, so that the number of times the patches are printed can be further reduced.

  Further, after the ink amount limit value is determined in step S30, a partial color conversion table on the achromatic color axis is generated using the ink amount limit value without additionally printing a patch (step S30). S40 to S70). Specifically, the ink usage amount of K ink or CMY ink associated with the representative value on the achromatic color axis is determined so as not to exceed the total limit value IMX_total. Also, a partial color conversion table on the achromatic color axis is generated (step S70) using the calibration table (step S50) generated using the ink amount limit value. As a result, in order to generate the partial color conversion table, no additional patches are printed, so that the number of times the patches are printed can be further reduced.

  Further, in step S60, the colorimetric values (measured values of L value, a value, and b value) of the virtual patch required for generating the achromatic color partial color conversion table are estimated (FIG. 8). . As a result, it is possible to generate an achromatic color axis partial color conversion table without actually printing a patch having a virtual patch color. As a result, an appropriate color conversion table can be generated without increasing the number of times the patch is printed.

  More specifically, the measurement value L_CMYK (β) of the L value of a specific CMYK mixed color patch printed using equal amounts β of four types of CMYK inks, and K ink is printed using the amount β. Using the measured value L_K (β) of the L value of a specific K single-color patch, three types of CMY inks are used in equal amounts α, and the virtual patch to be printed using the K ink amount β. The L value L_vir (α, β) is estimated (formula (5) in FIG. 10). As a result, an appropriate L value can be estimated without actually printing the virtual patch. Therefore, it is possible to reduce the number of times the patch is printed to obtain a necessary L value. As a result, the number of times of printing patches for generating the color conversion table can be reduced.

  Further, in the Lab value estimation process (FIG. 8), a virtual CMY usage amount IV_CLvir is determined (step S125), that is, a virtual patch is determined. The usage amount IV_CLvir is calculated using the measured value of the OD value of the CMYK single color patch when the usage amount of the ink of the CMYK mixed color patch to be processed exceeds the total limit value IMX_total (step S115: YES). Ink amount limit values IMX_CL, IMX_K, and IMX_total are determined (FIG. 9). That is, the virtual patch to be estimated can be printed only after printing and measurement of CMYK single-color patches when actually printing. In the above-described embodiment, the L value of the virtual patch can be estimated without printing an additional patch after printing the CMYK single-color patch. Therefore, it is possible to effectively suppress an increase in the number of times the patch is printed.

  Furthermore, in the Lab value estimation process (FIG. 8), when the ink usage of the CMYK mixed color patch to be processed does not exceed the total limit value IMX_total (step S115: NO), the virtual patch is not determined. As a result, since the brightness of a virtual patch that does not need to be estimated is not estimated, an increase in processing time can be suppressed.

  Further, in the Lab value estimation process (FIG. 8), the a value and b value of the virtual patch are estimated using the a value and b value of the single color patch of each specific ink amount of the three types of CMY inks. (FIG. 11). As a result, three types of CMY inks are used in equal amounts α and K ink is used in an amount β to estimate the a value and b value of a color to be printed without printing a patch of that color. be able to. Therefore, it is possible to reduce the number of times the patch is printed to obtain the necessary a value and b value. As a result, the number of times of printing patches for generating the color conversion table can be reduced.

B. Second embodiment:
In the second embodiment, a method for estimating the L value of a virtual patch (α, β) to be printed using three types of CMY inks of equal amounts α and K ink amounts β is used in the first embodiment. And different. FIG. 15 is a diagram illustrating the estimation of the L value L_vir (α, β) of the virtual patch (α, β) according to the second embodiment. In the second embodiment, for example, the CMY ink use amount α of the CMYK mixed color patch to be processed is fixed and the K ink use amount is reduced, that is, the K ink use amount β is calculated. Thus, the virtual patch (α, β) to be estimated is determined.

  In the second embodiment, the L value L_vir (α, β) is calculated using equation (9) in FIG. L_CMY (α) is a measured value of the L value of the CMY color mixture patch with the usage amount α. L_CMYK (α) is a measured value of the L value of the CMYK mixed color patch with the usage amount α. As can be seen from FIG. 10, in the first embodiment, L_vir (α, β) is estimated based on the L value L_K (β) of the K single-color patch with the usage amount β. Instead, as can be seen from FIG. 15, in the second embodiment, the L value L_vir (α, β) is estimated based on the L value L_CMY (α) of the CMY color mixture patch of the usage amount α.

  As shown in FIG. 15B, the absolute value of (L_CMYK (α) −L_CMY (α)) is the amount of change in the L value when K ink is added by the amount α to the CMY color mixture patch of the usage amount α. Represents. Therefore, (L_CMYK (α) −L_CMY (α)) × (β / α) represents the amount of change in the L value when K ink is added by the amount β to the CMY color mixture patch of the usage amount α. Conceivable. Since the virtual patch (α, β) is considered to be a patch obtained by adding the amount K of K ink to the CMY color mixture patch of the usage amount α, the virtual patch is expressed by using the equation (9) in FIG. The L value (brightness) of (α, β) can be estimated.

  As a result, as in the first embodiment, three types of CMY inks are used in equal amounts α and K ink is used in amounts β, and the L value of the color to be printed is actually printed on the patch of that color. Can be estimated without. As a result, it is possible to suppress an increase in the number of times the patch is printed in order to obtain a necessary L value.

  Specifically, the measured value L_CMYK (α) of the L value of a specific CMYK mixed color patch printed by using four equal amounts of CMYK color materials α and equal amounts of the three color materials CMYK. Using the measured value L_CMY (α) of the L value of a specific CMY mixed color patch printed using α at a time, three types of CMY inks are used in an equal amount α and K ink is used in an amount β. The L value L_vir (α, β) of the virtual patch to be printed is estimated (formula (9) in FIG. 15A). As a result, an appropriate L value can be estimated without actually printing the virtual patch. Therefore, it is possible to reduce the number of times the patch is printed to obtain a necessary L value. As a result, the number of times of printing patches for generating the color conversion table can be reduced.

C. Third embodiment:
In the third embodiment, a method for estimating the L value of a virtual patch (α, β) to be printed by using three types of CMY inks of equal amounts α and K ink amounts β is used in the first embodiment. And different. FIG. 16 is a diagram illustrating the estimation of the L value L_vir (α, β) of the virtual patch (α, β) according to the third embodiment.

  In the third embodiment, the L value L_vir (α, β) is calculated using the equation (10) in FIG. L_K (β) is a measured value of the L value of the K single-color patch with the usage amount β. L_CMYK (β) is a measured value of the L value of the CMYK mixed color patch with the usage amount β. As can be seen from FIG. 10, in the first embodiment, L_vir (α, β) is estimated based on the L value L_K (β) of the K single-color patch with the usage amount β. Instead, as can be seen from FIG. 16, in the third embodiment, the L value L_vir (α, β) is estimated based on the L value L_CMYK (β) of the CMYK color mixture patch of the usage amount β.

  As shown in FIG. 16B, the absolute value of (L_CMYK (β) −L_K (β)) is the amount of change in the L value when the K ink is subtracted by the amount β from the CMYK mixed color patch of the usage amount β. Represents. Therefore, {(((L_CMYK (β) −L_K (β)) × (β−α) / α)} is obtained when the K ink is subtracted by the amount (β−α) from the CMYK mixed color patch of the usage amount β. It is considered that it represents the amount of change in the L value. Since the virtual patch (α, β) is considered to be a patch obtained by subtracting K ink by (β−α) from the CMYK mixed color patch of the usage amount β, the equation (10) in FIG. The L value (brightness) of the virtual patch (α, β) can be estimated.

  As a result, as in the first embodiment, three types of CMY inks are used in equal amounts α and K ink is used in amounts β, and the L value of the color to be printed is actually printed on the patch of that color. Can be estimated without. As a result, it is possible to suppress an increase in the number of times the patch is printed in order to obtain a necessary L value.

  Specifically, the measurement value L_CMYK (β) of the L value of a specific CMYK mixed color patch that is printed using equal amounts β of four types of CMYK inks, and the K ink is printed using the amount β. Using the measured value L_K (β) of the L value of a specific K single color patch, three types of CMY inks are used in equal amounts α, and the L of the virtual patch to be printed using the K ink amount β. The value L_vir (α, β) is estimated (formula (10) in FIG. 16A). As a result, an appropriate L value can be estimated without actually printing the virtual patch. Therefore, it is possible to reduce the number of times the patch is printed to obtain a necessary L value. As a result, the number of times of printing patches for generating the color conversion table can be reduced.

D. Variation:
(1) In each of the above embodiments, the CPU 210 uses three types of CMY inks of equal amounts α and uses K ink amount β, and the L value of a virtual patch (α, β) to be printed, a Value and b value are estimated. It is not limited to this. For example, N types of ink (N is a natural number of 3 or more), for example, three or more types of known inks such as cyan, magenta, yellow, black, light cyan, and light magenta used for printing are used for printing. Consider the case where it is used. In this case, for example, the CPU 210 uses the equal amount α of (N−1) types of ink and the amount β of the remaining one type of ink for the virtual patch (α, β) to be printed. You may estimate L value, a value, and b value.

  For example, when using the same method as in the first embodiment and the third embodiment, the CPU 210 uses the measured value of the L value of a specific patch printed using equal amounts β of N types of ink, It is preferable to estimate the L value of the virtual patch (α, β) using the measured value of the L value of a specific patch printed by using the remaining one type of ink as described above.

  In the case of using the same method as that of the second embodiment, the CPU 210 performs measurement of the L value of a specific patch printed by using an equal amount α of N kinds of color materials, and (N−1). It is preferable to estimate the L value of the virtual patch (α, β) using the measured value of the L value of a specific patch printed using the amount α of each kind of ink.

  Further, it is preferable that the CPU 210 estimates the a value and the b value of the virtual patch (α, β) by using the a value and the b value of each specific single color patch of the N kinds of color materials.

(2) In the second embodiment, the CPU 210 fixes the amount of K ink to β when determining the virtual patch of the CMYK mixed-color patch printed by using the same amount β of four types of CMYK inks. In addition, the amount of CMY ink is decreased from β to α so as not to exceed the total limit value IMX_total. Instead, the CPU 210 may fix the amount of CMY ink to β and decrease the amount of K ink so as not to exceed the total limit value IMX_total. Further, the CPU 210 may reduce both the CMY ink amount and the K ink amount so as not to exceed the total limit value IMX_total.

(3) Each of the patch groups 11 to 19 of the patch sheet 10 of the above embodiment includes a plurality of patches whose ink usage is changed at regular intervals (for example, in increments of 1%). Instead of this, the interval of the amount of ink used between the plurality of patches may not be equal. For example, based on the approximate shape of the predicted calibration table, the range of ink usage for which patches should be prepared at relatively narrow intervals and the range of ink usage for which patches should be prepared at relatively wide intervals are predicted. it can. Based on such prediction, the interval of the ink usage between patches may be set to a different value for each of a plurality of ranges of usage. In this way, the number of patches to be printed can be reduced.

(4) The measured value of the patch and the estimated value estimated from the measured value of the patch are not limited to the L value, the a value, the b value, and the OD value. For example, component values of other color systems such as the CIEXYZ color system may be included. In general, a measured value of a patch and an estimated value estimated from the measured value of the patch are a value indicating brightness (L value in the embodiment) and a value related to at least one of hue and saturation (implementation). In the example, it is preferable to include at least one of a value and b value).

(5) In each of the above-described embodiments, the creation of the color conversion table used in the ink jet printer 200 has been described. However, a similar method can be used to create the color conversion table used in the laser printer. . In this case, for example, a color conversion table for converting RGB color data into color data including a plurality of types of color components corresponding to a plurality of types of toner used can be created.

(6) In each of the above embodiments, the control device of the printer 200 executes the color conversion table generation process. However, a system including the printer may execute the color conversion table generation process. For example, a color conversion table generation process may be executed in cooperation by a printer as a print execution unit, a colorimeter separate from the printer, and a computer such as a personal computer. For example, the computer may supply patch data to a printer to print the patch sheet 10 (FIG. 3) (step S10 in FIG. 2). Then, the colorimeter may measure the color of each patch on the patch sheet 10 and supply the colorimetric data to the computer (step S20 in FIG. 2). Then, the computer may generate the color conversion table by executing the processing from steps S30 to S80 in FIG. 2 using the colorimetric data.

(7) The color conversion table to be generated is not limited to a table that associates RGB color system color data with CMYK color system color data. For example, a table for associating color data of the YCrCb color system and color data of the CMYK color system may be generated.

(8) In the above embodiment, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced with hardware. Also good.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

    10 ... patch sheet, 200 ... multifunction machine, 200 ... printer, 210 ... CPU, 220 ... volatile storage device, 230 ... nonvolatile storage device, 231 ... program, 232 ... Patch data, 240 ... Print mechanism, 250 ... Scanner unit, 260 ... Operation unit, 270 ... Display unit, 280 ... Communication unit, 290 ... Colorimeter

Claims (11)

A processing device for acquiring color values indicating a plurality of colors printed using N types (N is a natural number of 3 or more) of color materials,
An acquisition unit that acquires a lightness measurement value of a plurality of first mixed color patches having different densities and a lightness measurement value of a plurality of first single color patches having different densities. Each of the one mixed color patch is printed using an equal amount of N kinds of color materials, and each of the plurality of first single color patches is used by one kind of color material among the N kinds of color materials. The acquisition unit printed and printed,
Among the plurality of first mixed color patches, the lightness measurement value of a specific first mixed color patch printed using the same amount β of the N kinds of color materials, and the plurality of first single color patches. Among them, an estimation unit for estimating the brightness of a virtual patch using a measurement value of the brightness of a specific first single-color patch printed by using the amount β of the one type of color material, the virtual patch Is a patch to be printed by using (N-1) types of color materials of the N types by an equal amount α and using the remaining one of the N types of color materials by an amount β. The estimating unit;
A processing apparatus. A processing device for acquiring color values indicating a plurality of colors printed using N types (N is a natural number of 3 or more) of color materials,
An acquisition unit that acquires a lightness measurement value of a plurality of first color mixture patches having different densities and a lightness measurement value of a plurality of second color mixture patches having different densities. Each of the mixed color patches is printed by using an equal amount of the N types of color materials, and each of the plurality of second mixed color patches is (N-1) types of the N types of color materials. The acquisition unit printed using equal amounts of the color material
Among the plurality of first mixed color patches, the lightness measurement value of a specific first mixed color patch printed using the N kinds of color materials in equal amounts α, and the plurality of second mixed color patches. Among them, an estimation unit that estimates the lightness of the virtual patch using the measured value of the lightness of the specific second mixed color patch printed by using the (N-1) types of color materials in equal amounts α. The virtual patch is a patch to be printed by using (N-1) kinds of color materials in an equal amount α and using the remaining one of the N types of color materials in an amount β. And the estimator,
A processing apparatus comprising: The processing apparatus according to claim 1 or 2, wherein
The N types of color materials include cyan, magenta, yellow, and black color materials,
The (N-1) types of color materials of the virtual patch include cyan, magenta, and yellow color materials,
The processing apparatus, wherein the one type of color material of the virtual patch includes a black color material. The processing apparatus according to claim 3,
The acquisition unit further includes:
The measurement value of the brightness of a plurality of first single color patches printed using the black color material and having different densities is obtained.
Lightness measurement values of a plurality of second single color patches printed using one of the (N-1) types of color materials and having different densities are used as the (N-1) types of color materials. Get for each of the coloring materials,
The processing apparatus further includes:
A determination unit that determines whether the first mixed color patch having a specific density is a patch that exceeds a limit value of a color material usage amount;
When the first mixed color patch having the specific density is a patch that exceeds the use amount limit value, the first single color patch and the second single color patch are set so as not to exceed the use amount limit value. A determination unit that determines at least one of the amounts α and β of the color material of the virtual patch using the measured value of brightness of
With
The processing unit is configured to estimate a measured value of brightness of the determined virtual patch. The processing apparatus according to claim 4,
The processing unit, wherein the determination unit does not determine the virtual patch when the first mixed color patch having the specific density is a patch that does not exceed the use amount limit value. The processing apparatus according to claim 4 or 5, wherein
The acquisition unit further includes:
Obtaining a measurement value of a specific color component of the plurality of first single color patches;
The measurement values of the specific color component of the plurality of second single color patches are acquired for each of the (N-1) types of color materials,
The specific color component is a color component related to at least one of hue and saturation,
The estimation unit further determines the value of the specific color component of the virtual patch, the measured value of the specific color component of the specific first single color patch, and (N-1) of the (N-1) types of color materials. And a measured value of the specific color component of each specific second single color patch. The processing apparatus according to any one of claims 1 to 6, further comprising:
Using the estimated lightness of the virtual patch, the first color data of the first color system and the second color system of the second color system having a plurality of components corresponding to the plurality of types of color materials. A generation unit that generates a table that associates color data with
A target brightness is associated with the first color data,
The processing apparatus, wherein the first color data is associated with the second color data representing a color having the target brightness. A processing device for obtaining color values indicating a plurality of colors printed using N kinds of color materials (N is a natural number of 3 or more),
An acquisition unit that acquires, for each of the N color materials, measurement values of specific color components of a plurality of single-color patches that are printed using one type of color material and have different densities. Is the color component related to at least one of hue and saturation, and the acquisition unit;
An estimation unit that estimates a value of the specific color component of a virtual patch using a measurement value of the specific color component of each specific single color patch of the N types of color materials, wherein the virtual patch is the N (N-1) types of color materials of the types are used for each equal amount α, and the remaining one of the N types of color materials is a patch to be printed using the amount β. And
A processing apparatus. The processing apparatus according to claim 8, wherein
The estimated value of the specific color component of the virtual patch is the measured value of the specific color component of each specific single color patch of the N kinds of color materials or the measurement of the specific color component of the specific single color patch. A processing apparatus, which is a sum of interpolation values calculated for each of the N types of color materials based on a value. A method for obtaining color values indicating a plurality of colors printed using N kinds (N is a natural number of 3 or more) of color materials,
(A) a step of obtaining a lightness measurement value of a plurality of first color-mixed patches having different densities and a lightness measurement value of a plurality of first single-color patches having different densities; Each of the first mixed color patches is printed using N types of color materials in equal amounts, and each of the plurality of first single color patches is one type of the N types of color materials. Is used to be printed, and
(B) Among the plurality of first color mixture patches, a lightness measurement value of a specific first color mixture patch printed using an equal amount β of the N kinds of color materials, and the plurality of first color patches. A step of estimating the lightness of a virtual patch using a measured value of the lightness of a specific first single-color patch printed using the amount β of the one type of color material among the single-color patches, The virtual patch should be printed by using (N-1) types of color materials of the N types in equal amounts α and using the remaining one of the N types of color materials in an amount β. A process that is a patch,
A method comprising: A computer program for obtaining color values indicating a plurality of colors printed using N kinds (N is a natural number of 3 or more) of color materials,
An acquisition function for acquiring a lightness measurement value of a plurality of first color mixture patches having different densities and a lightness measurement value of a plurality of first single color patches having different densities. Each of the one mixed color patch is printed using an equal amount of N kinds of color materials, and each of the plurality of first single color patches is used by one kind of color material among the N kinds of color materials. The acquisition function being printed,
Among the plurality of first mixed color patches, the lightness measurement value of a specific first mixed color patch printed using the same amount β of the N kinds of color materials, and the plurality of first single color patches. An estimation function for estimating the lightness of a virtual patch using a lightness measurement value of a specific first single-color patch printed using the amount β of the one type of color material, the virtual patch Is a patch to be printed by using (N-1) types of color materials of the N types by an equal amount α and using the remaining one of the N types of color materials by an amount β. The estimation function;
A computer program that causes a computer to realize

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