JP2006086968A - Image processing apparatus, method thereof and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a colorimetric color separation table in an ink system consisting of key colors of cyan, magenta, yellow and black, high saturation specific color inks and light color inks obtained by thinning the key colors. <P>SOLUTION: In forming eight-color separation table in which a three-dimensional input signal (RGB) is separated into CMYKLcLmRdGr, a process is divided into a step of realizing separation of the specific color from RGB into CMYKRdGr, and a step of realizing of contrast separation from CMYKRdGr into CMYKLcLmRdGr. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus, a method, and a recording medium for a color printer, and more particularly, to a method for selecting a color separation table for separating color material (ink, toner) colors used in a color printer. It is.

  Conventionally, the image processing technology of a color printer is configured as shown in FIG. In FIG. 6, 601 is a color matching processing unit, 602 is a color separation processing unit, 603 is an output γ correction processing unit, 604 is a halftone processing unit, 605 is a color printer engine unit, 606 is a color separation table unit, and 607 is an output. Reference numeral 608 denotes a maximum total ink amount, and 609 denotes a printing paper (printing medium). Reference numeral 601 denotes a color matching processing unit for matching the color reproduction characteristics of the input image data RGB with the color of the printer. Reference numeral 602 denotes a color separation table unit 606 that converts input multi-value R′G′B ′ image data. Is separated into cyan C, magenta M, yellow Y, and black K, which are color material colors (hereinafter referred to as ink colors) of the color printer, by interpolation processing such as tetrahedral interpolation. The multivalued CMYK data output from the color separation processing unit 602 is corrected by the output γ correction processing unit 603 through the CMYK one-dimensional LUT according to the color reproduction characteristics of the color printer engine, Multi-value C'M'Y'K 'is output. By this processing, correction processing according to the characteristics of the color printer is realized. Here, in the image processing system, the maximum CMYK total ink amount used is defined by the combination of the color separation table unit 606 and the output γ correction table unit 607. The halftone processing unit 604 performs halftone processing for binarizing the corrected multi-value C′M′Y′K ′ data to the number of gradations that can be printed by a color printer, for example, a binary printer. The C "M" Y "K" binary data is output. The color printer engine unit 904 performs printing based on the input C "M" Y "K" binary data. Reference numeral 608 denotes a maximum value of the CMYK total ink amount that can be accepted by the print media A to E indicated by 609.

In this conventional technology,
As a table for printing processing on the print medium A, a color separation table part A and an output γ correction table A are
As a table for printing processing on the print medium B, a color separation table section B and an output γ correction table B are
As a table for performing print processing on the print medium C, a color separation table unit C and an output γ correction table C are provided.
A color separation table and an output γ correction table are prepared so as to be optimal for each medium. For example, since the maximum allowable CMYK total ink amount of the print medium A is 200%, the maximum CMYK total ink amount specified by the combination of the color separation table unit A and the output γ correction table A is , 200% is set. Similarly, for the print media B and C, the maximum allowable CMYK total ink amount is set to 250% and 300% (Patent Document 1).
JP 2001-136401 A

  However, in the above-described conventional example, since a color separation table and an output γ correction table corresponding to each print medium are prepared, the output γ correction table is not suitable for a new print medium that is not assumed in advance. There is a problem that the γ correction is not suitable and the output γ characteristic is biased. Similarly, there is no suitable color separation table for the color separation table. Therefore, when a color separation table having a large maximum CMYK total ink amount is used, the ink absorption allowable amount of the print medium is exceeded. There is a problem that the ink overflows. In addition, when a color separation table having a small maximum CMYK total ink amount is used, the maximum CMYK total ink amount can be increased even though the color reproduction range can be enlarged using more inks. Since a small color separation table is used, there is a problem that the color reproduction range becomes small. Furthermore, when trying to create a color separation table suitable for a new print medium that is not assumed in advance, a complicated process is required, so it takes a lot of time to create and cannot be easily created. There was a problem.

  Accordingly, an object of the first invention according to the present application is to provide an image processing apparatus and method capable of easily setting a suitable color separation table and an optimum output γ correction table even for a new print medium that is not assumed in advance. And to propose a recording medium.

  In order to achieve the above object, a first invention according to the present invention comprises the following arrangement.

In an image processing apparatus for processing color separation from a color image signal to a color material color in a color image forming apparatus using an LUT,
Γ correction table means for correcting the γ characteristic of the printed matter for each color material color, a plurality of color separation table means set so that the maximum value of the total color material amount is stepwise different, and the plurality of color separation tables A maximum total color material amount calculating means for calculating the maximum value of the total color material amount for each combination of the means and the γ correction table means; and a maximum total color material amount setting means for setting the maximum total color material amount; Means for selecting an optimum color separation table means from the plurality of color separation table means based on the results of the maximum total color material amount setting means and the maximum total color material amount calculation means; and the selected color separation And a means for executing color separation processing into the color material color based on the table means.

  In the above configuration, by using the corrected γ correction table, the γ characteristics of CMYK single colors are corrected and the biased output γ characteristics are calibrated. In addition, by selecting an optimal color separation table from a plurality of color separation table means set so that the maximum value of the total color material amount is different in stages, the complexity required when creating a new one is created. Color separation processing can be realized by using a color separation table suitable for a new print medium that is not assumed without requiring much time for processes and creation. As a result, it is possible to solve the problems such as the ink absorption amount exceeding due to the incompatibility of the color separation table and the problem that the color reproduction range of the printed material becomes small.

  According to the present invention, for a new print medium that has not been assumed, the monochromatic γ characteristic of the color material color of the color printer is corrected and a complicated process and a large amount for the creation are required. Color separation processing can be realized by using a color separation table suitable for a new print medium that is not assumed without requiring a long time. As a result, it is possible to solve the problems such as the ink absorption amount exceeding due to the incompatibility of the color separation table and the problem that the color reproduction range of the printed material becomes small.

  The best mode for carrying out the present invention will be described below based on examples.

(First embodiment)
FIG. 1 is a diagram best representing the features of the present invention, and the configuration of the present invention is shown in a block diagram. In FIG. 1, 101 is a color matching processing unit, 102 is a color separation processing unit, 103 is an output γ correction processing unit, 104 is a halftone processing unit, 105 is a color printer engine unit, 106 is a maximum total ink amount setting unit, 107 is a color separation table selection unit, and 108 is a color separation table unit. A to E so that the maximum total value of the total amount of CMYK inks changes stepwise. The five-stage color separation table is stored. Reference numeral 109 denotes an output γ correction table unit, which is one-dimensional corresponding to color material colors (ink colors) C (cyan), M (magenta), Y (yellow), and K (black) used in the color printer 203. It is composed of the table. Reference numeral 110 denotes a maximum total ink amount calculation unit, and reference numeral 111 denotes an output γ correction table creation unit. A color matching processing unit 101 matches the color reproduction characteristics of the input image data RGB with the colors of the printer. Based on the content of the built-in color matching table, the RGB image data is subjected to tetrahedral interpolation processing or cube interpolation processing. A color matching process is executed by a three-dimensional interpolation process such as the above, and color conversion to R′G′B ′ is performed. Reference numeral 102 denotes a color separation processing unit. Based on the results from the maximum total ink amount setting unit 106 and the maximum total ink amount calculation unit 110, the color separation table selection unit 107 selects a suitable color from the color separation table unit 108. A decomposition table is selected. The color separation processing unit 102 performs color material color (ink color) C (cyan), M (masent) of the color printer by three-dimensional interpolation processing such as tetrahedral interpolation processing and cube interpolation processing based on the selected color separation table. , Y (yellow), K (black) for color separation processing is executed. Reference numeral 103 denotes an output γ correction processing unit for correcting CMYK color material color data for γ characteristics due to the combination of the processing content of the halftone processing unit 104 and the color printer engine unit 105. A halftone processing unit 104 is a halftone process for converting C′M′Y′K ′ multi-value data from the output γ correction processing unit 103 into the number of gradations that can be expressed by the color printer engine unit 105. Part. A color printer engine unit 105 performs development printing processing based on C "M" Y "K" from the halftone processing unit 104.

  Hereinafter, a method for creating an output γ correction table suitable for a target print medium and a method for selecting a suitable color separation table will be described in detail with reference to FIG. FIG. 2 shows an example of a system configuration including a color printer in which the present invention is implemented. In FIG. 2, 201 is a computer for controlling the color printer and the colorimeter, and 202 is held in the computer 201. A monitor 203 for displaying data and the like, 203 is a color printer for printing image data, and 204 is a colorimeter for measuring colors of patches printed by the color printer 203. 205 denote patches printed by the color printer 203. The present embodiment shown in FIG. 1 is implemented in the color printer 203 in FIG.

  FIG. 3 is a flowchart for explaining a method for creating a new output γ correction table for a target print medium and a method for selecting a suitable color separation table.

  In FIG. 3, step S301 is a start step, and S302 is a printing step for a gamma correction patch. Image processing from the halftone processing unit 104 to the color printer engine unit 105 in FIG. Processing is executed. The printed result is shown in the print patch 205 in FIG. As shown in the figure, the print patch 205 prints the gradation characteristics of the primary colors of CMYK, which are the color material colors of the color printer 203, as a patch. S303 is a color measurement step for the γ correction patch. The print patch 205 in FIG. 2 is measured using the colorimeter 204, and the result is transmitted to the computer 201. In the computer 201, the color measurement result is transferred to the image processing apparatus in the color printer 203. S304 is an output γ correction table creation step. The output γ correction table creation unit 111 creates an output γ correction table based on the colorimetry result from the computer 201, and the result is the output γ correction table unit 109. Transferred to and stored. FIG. 4 is a diagram showing the color measurement results, and shows the density characteristics of the print results with respect to the halftone processing unit input signal (C′M′Y′K ′). As is apparent from FIG. 4, when the output γ correction is not performed on a new medium that is not assumed, nonlinear characteristics are obtained. Therefore, as shown in FIG. 5, a one-dimensional output γ correction table is created for each CMYK color material color so that the printing characteristics are linear with respect to the ink amount signal (CMYK). Next, S305 is a step of calculating a color separation table maximum total ink amount. The maximum total ink amount calculation unit 110 performs the five color separation tables A to E of the color separation table unit 108 and the output γ correction table unit 109. The maximum total ink amount in five stages is calculated on the basis of the contents of. S 306 is a step of setting the maximum total ink amount, and the setting content is stored in the maximum total ink amount setting unit 106. Step S <b> 307 is a color separation table selection step, and the color separation table selection unit 107 selects a suitable color separation table from the color separation table unit 108. For example, the result set in the maximum total ink amount setting step S306 is 255%, and the results corresponding to the color separation tables A to E calculated in the color separation table maximum total ink amount calculating step S305 are shown. In the case of 200%, 220%, 240%, 260%, and 280%, respectively, in the color separation table selection step S307, the maximum total ink amount closest to 255% with a value larger than the set 255% is 260. % Color separation table D is selected.

  As described above, a plurality of color separation tables are prepared so that the maximum total value of the total ink amount of CMYK inks changes stepwise, and the output γ characteristic is obtained for a new print medium that is not assumed in advance. An output γ correction table for correction is created. Then, a maximum total ink amount corresponding to each color separation table is calculated from a plurality of color separation tables and an output γ correction table, and a suitable color separation table is calculated from the calculated maximum total ink amount and the set maximum total ink amount. And the color separation process is executed using the selected color separation table. By performing a series of these processes, γ correction is performed even on a new print medium that is not assumed, so that the problem that the γ characteristics of CMYK single colors are biased is solved. In addition, by selecting a color separation table suitable for the print medium from the color separation tables prepared so that the maximum total value of the CMYK total ink amount varies step by step, the ink absorption allowable amount is exceeded. And the problem that the color reproduction range becomes small is solved. Furthermore, since a plurality of color separation tables are prepared in advance, suitable color separation processing can be realized without creating a new color separation table even for a new print medium that is not assumed in advance.

(Second embodiment)
In the first embodiment, the ink system uses four colors of cyan, magenta, yellow, and black as the color material colors of the color printer. However, the configuration of the ink system is not limited to this, and light cyan ink or A color printer may be a six-color ink system using light magenta ink or an ink system using other colors such as red and green. Needless to say, the color material can be applied not only to ink but also to a system such as toner used in electrophotography.

It is a figure which best represents the characteristic of 1st Example, and is a block diagram which shows the structure of this invention. An example of a system configuration including a color printer in which the present invention is implemented is shown. 6 is a flowchart for explaining a method for creating a new output γ correction table for a target print medium and a method for selecting a suitable color separation table. A density characteristic of a print patch of a primary color of CMYK which is a color material color of a color printer for a new print medium is shown. FIG. 6 is a diagram showing density characteristics as a result of output γ correction. It is a figure for demonstrating a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Color matching process part 102 Color separation process part 103 Output gamma correction process part 104 Halftone process part 105 Color printer engine part 106 Maximum total ink amount setting part 107 Color separation table selection part 108 Color separation table part 109 Output gamma correction table part 110 Maximum Total Ink Amount Calculation Unit 111 Output γ Correction Table Creation Unit 201 Computer 202 Monitor 203 Color Printer 204 Colorimeter 205 Print Patch S301 Start Step S302 Print γ Correction Patch Step S303 γ Correction Patch Color Measurement Step S304 Output Gamma correction table creation step S305 Color separation table maximum total ink amount calculation step S306 Maximum total ink amount setting step S307 Color separation table selection step S308 End step 601 Tatching processing unit 602 Color separation processing unit 603 Output gamma correction processing unit 604 Halftone processing unit 605 Color printer engine unit 606 Color separation table unit 607 Output gamma correction table unit 608 Maximum total ink amount 609 Print media

Claims (10)

In an image processing apparatus for processing color separation from a color image signal to a color material color in a color image forming apparatus using an LUT,
Γ correction table means for correcting the γ characteristic of the printed matter for each color material color, a plurality of color separation table means set so that the maximum value of the total color material amount is stepwise different, and the plurality of color separation tables A maximum total color material amount calculating means for calculating the maximum value of the total color material amount for each combination of the means and the γ correction table means; and a maximum total color material amount setting means for setting the maximum total color material amount; Means for selecting an optimum color separation table means from the plurality of color separation table means based on the results of the maximum total color material amount setting means and the maximum total color material amount calculation means; and the selected color separation An image processing apparatus comprising: means for performing color separation processing on the color material color based on table means. In an image processing apparatus for processing color separation from a color image signal to a color material color in a color image forming apparatus using an LUT,
A means for printing a patch for gamma correction for each color material color; a means for measuring the color of the printed patch; a means for creating a gamma correction table based on the colorimetric result; Γ correction table means to be held, a plurality of color separation table means set so that the maximum value of the total color material amount is stepwise different, and a combination of the plurality of color separation table means and the γ correction table means A maximum total color material amount calculating means for calculating a maximum value of the total color material amount; a maximum total color material amount setting means for setting a maximum total color material amount; and the maximum total color material amount setting means and the maximum Means for selecting an optimum color separation table means from among the plurality of color separation table means based on the result of the total color material amount calculating means; and color to the color material color based on the selected color separation table means With the means to perform the decomposition process An image processing apparatus configured to be configured. The color material color according to claim 1 or 2,
An image processing apparatus comprising a total of four colors of cyan, magenta, yellow, and black. The color material color according to claim 1 or 2,
An image processing apparatus comprising a total of six colors of cyan, magenta, yellow, black, and light cyan and light magenta. In an image processing method for processing color separation from a color image signal into a color material color in a color image forming method using an LUT,
A γ correction table step for correcting the γ characteristic of the printed material for each color material color, a plurality of color separation table steps set so that the maximum value of the total color material amount is stepwise different, and the plurality of color separation tables A maximum total color material amount calculating step for calculating the maximum value of the total color material amount for each combination of the step and the γ correction table step; and a maximum total color material amount setting step for setting the maximum total color material amount; Selecting an optimum color separation table step from the plurality of color separation table steps based on the results of the maximum total color material amount setting step and the maximum total color material amount calculation step; and the selected color separation An image processing method comprising: performing color separation processing on the color material color based on a table step. In an image processing method for processing color separation from a color image signal into a color material color in a color image forming method using an LUT,
A step of printing a gamma correction patch for each color material color, a step of measuring the color of the printed patch, a step of creating a gamma correction table based on the colorimetric result, and the gamma correction table Γ correction table step to be held, a plurality of color separation table steps set so that the maximum value of the total color material amount is stepwise different, and for each combination of the plurality of color separation table steps and the γ correction table step A maximum total color material amount calculating step for calculating the maximum total color material amount, a maximum total color material amount setting step for setting the maximum total color material amount, the maximum total color material amount setting step, and the maximum Selecting an optimal color separation table step from the plurality of color separation table steps based on the result of the total color material amount calculating step; and the selected color separation table An image processing method comprising: performing color separation processing on the color material color based on a color step. The color material color according to claim 5 or 6 is:
An image processing method comprising four colors of cyan, magenta, yellow, and black. The color material color according to claim 5 or 6 is:
An image processing method comprising a total of six colors of cyan, magenta, yellow, black, and light cyan and light magenta. In a medium for recording a program for realizing an image processing method for processing color separation from a color image signal to a color material color in a color image forming method using an LUT,
A γ correction table step for correcting the γ characteristic of the printed material for each color material color, a plurality of color separation table steps set so that the maximum value of the total color material amount is stepwise different, and the plurality of color separation tables A maximum total color material amount calculating step for calculating the maximum value of the total color material amount for each combination of the step and the γ correction table step; and a maximum total color material amount setting step for setting the maximum total color material amount; Selecting an optimum color separation table step from the plurality of color separation table steps based on the results of the maximum total color material amount setting step and the maximum total color material amount calculation step; and the selected color separation And a step of executing color separation processing into the color material color based on a table step. In a medium for recording a program for realizing an image processing method for processing color separation from a color image signal to a color material color in a color image forming method using an LUT,
A step of printing a gamma correction patch for each color material color, a step of measuring the color of the printed patch, a step of creating a gamma correction table based on the colorimetric result, and the gamma correction table Γ correction table step to be held, a plurality of color separation table steps set so that the maximum value of the total color material amount is stepwise different, and for each combination of the plurality of color separation table steps and the γ correction table step A maximum total color material amount calculating step for calculating the maximum total color material amount, a maximum total color material amount setting step for setting the maximum total color material amount, the maximum total color material amount setting step, and the maximum Selecting an optimal color separation table step from the plurality of color separation table steps based on the result of the total color material amount calculating step; and the selected color separation table And a step of executing a color separation process into the color material color based on a color step.

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