JP2006191497A - Color gamut compression device, color gamut compression method, color gamut compression program, and the like - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color gamut compression device etc, capable of more naturally reproducing colors in consideration of differences of color gamuts among devices with respect to a technical field of the color gamit compression device etc. in a color DTP system. <P>SOLUTION: The color gamut compression device compresses a color gamut of a second device when a color gamut of a first device is narrower than the color gamut of the second device as a target. The color gamut compression device includes; a means for acquiring a plurality of first chrominance signal data representing a chrominance signal relating to the first device and a plurality of second chrominance signal data representing a chrominance signal relating to the second device; a means for converting the outermost chrominance signal data being outside a color gamut indicated by first gamut data so that it is within a color gamut indicated by the first color gamut data; and a means for interpolating a high saturation area on the basis of first chrominance signal data acquired by the chrominance signal data acquisition means, of second chrominance signal data left after removal by a removal means, and of converted outermost chrominance signal data. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technical field such as a color gamut compression device in a color DTP system, and particularly when the color gamut of a first device is smaller than the color gamut of a target second device. The present invention relates to a color gamut compression device and the like that can perform more natural color reproduction in consideration of the difference.

  In general, the color gamut of a device such as a printer or monitor that handles a color image, that is, the shape of the color reproduction range (Gamut), is different for each device. For example, the printer performs color reproduction with cyan (C), magenta (M), yellow (Y), and black (K) inks, but the color reproduction range (Gamut) (hereinafter referred to as “gamut”) that is actually printed by the printer. The color gamut is different depending on the characteristics of the ink used and the type of printing paper used as an image recording medium.

  By the way, when selling large commercial printers such as offset printers, in order to check the color reproducibility etc. of the commercial printers, print color charts and print test photos etc. Then, it is conceivable to perform sales promotion activities and sales activities by showing the printed matter to customers. In this way, each time a printed matter is presented to a customer, an inkjet printer provided at each sales office, etc., taking into account the trouble of printing with the business printing device to be sold, the operating cost of the business printing device, etc. General-purpose small-sized printing apparatuses may output (print) printed matter having the color reproducibility of a commercial printing apparatus to be sold.

  In such a case, the color gamut of the general-purpose small printing device is adjusted to the color gamut of the commercial printing device in order to perform color reproduction on the commercial printing device to be sold with a general-purpose small printing device such as an inkjet printer. There is a need to. Thus, the concept of device-independent color reproduction technology (Device Independent Color) that attempts to reproduce the same color between devices has been demanded. A system for realizing this device independent color reproduction technology (Device Independent Color) is generally called a color management system (CMS).

  This color management system uses, for example, conversion formulas or conversion tables called profiles to convert input color signals to output signals when connecting various input / output devices such as cameras, scanners, monitors, and printers. This is realized by once converting to a common color space independent of devices (such as 1976 CIELab space defined by the International Commission on Illumination (CIE)).

  In the above color management system, if the color gamut of the general-purpose small printing device is larger than the color gamut of the commercial printing device, the general-purpose small printing device can print the printed matter having the color reproducibility of the commercial printing device. However, if the color gamut of a commercial printing device is larger than the color gamut of a general-purpose small printing device, the color information cannot be accurately reproduced as it is depending on the color chart or print test photograph. . For example, when a printed matter having color reproducibility in a commercial printing device is printed by a general-purpose small printing device, the color gamut of the general-purpose small printing device is smaller than that of the commercial printing device, so the reproduction of the general-purpose small printing device Colors outside the range cannot be reproduced as they are. Therefore, in such a case, it is necessary to perform color correction processing that keeps the color information in the commercial printing apparatus as much as possible and brings colors out of the color gamut within the reproduction range of the general-purpose small-sized printing apparatus.

  In general, this process of pushing (compressing) a physically unreproducible color into the color gamut by some processing is called color gamut compression (Gamut Compression). Techniques related to compression techniques are disclosed.

JP 2002-118764 A JP-A-11-341296 JP-A-9-98998 Japanese Patent Laid-Open No. 7-236069

  Conventionally known compression methods do not convert colors that are in the color gamut of general-purpose compact printers among colors that can be reproduced by commercial printers, but only clips out of the color gamut into the color gamut ( However, such a method has a problem that the gradation of a high saturation portion such as the vicinity of the color gamut boundary of a general-purpose small printing apparatus is deteriorated.

  To solve this problem, a method has been proposed that compresses all colors so that all colors that can be reproduced by a commercial printing device fall within the color gamut of a general-purpose small printing device. There is a problem in that the conversion accuracy is lowered and further calculation time is required, so that a quick compression process cannot be performed.

  Therefore, the present invention has been made in view of the above problems, and in a color DTP system, a color gamut compression method and color gamut compression that enable more natural color reproduction in consideration of the color gamut of each device. An object is to provide a device.

  In order to solve the above-mentioned problem, the invention according to claim 1 is configured such that when the color gamut of the first device is smaller than the target color gamut of the second device, the color gamut of the second device is set. A color gamut compression device that compresses a plurality of first chromaticity signal data indicating a chromaticity signal related to the first device, and a plurality of second chromaticity signals related to the second device. Chromaticity signal data acquisition means for acquiring chromaticity signal data; first gamut data indicating a gamut of a first device based on the first chromaticity signal data; and Gamut data acquisition means for acquiring second gamut data indicating the gamut of the second device based on the chromaticity signal data of the second gamut data, and the first gamut of the second chromaticity signal data Second chromaticity signal data present in the color gamut of the first device indicated by the data. 2nd chromaticity signal data belonging to the high chroma region including the second chromaticity other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second color gamut data Removal means for removing signal data and the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data are converted so as to be within the color gamut indicated by the first color gamut data. The first chromaticity signal data acquired by the conversion means, the chromaticity signal data acquisition means, the remaining second chromaticity signal data after removal by the removal means, and the conversion means converted by the conversion means Interpolation means for interpolating the high saturation region based on the outermost chromaticity signal data is provided.

  According to this, among the second chromaticity signal data that can be reproduced by the second device, the second chromaticity signal data belonging to the high saturation region, and other than the outermost chromaticity signal data, The chromaticity signal data of 2 is removed, the outermost chromaticity signal data is converted to be within the color gamut of the first device, and the converted outermost chromaticity signal data and the second color remaining without being removed are converted. Since the high saturation area is interpolated based on the degree signal data and the acquired first chromaticity signal data, the area changes smoothly near the threshold of the color gamut (high saturation area), and the first The entire color gamut can be quickly compressed without changing the inside of the device gamut, realizing high color conversion accuracy and high gradation reproducibility before and after gamut compression. It becomes possible to do.

  In order to solve the above-mentioned problem, the invention according to claim 2 is directed to the second printing apparatus when the color gamut of the first printing apparatus is smaller than the target color gamut of the second printing apparatus. A color gamut compression device that compresses a color gamut, the color gamut compression color chart printed by the first printing device and the second printing device, wherein the color gamut of the second printing device is The color chart for color gamut compression in which there is no color data in a high saturation area other than the outermost chromaticity signal data belonging to the outermost area of the color gamut indicated by the second color gamut data shown, Chromaticity signal data for acquiring a plurality of chrominance signals related to the printing apparatus and the second printing apparatus, respectively, and acquiring second chromaticity signal data and first chromaticity signal data based on the respective color signals Based on the acquisition means and the first chromaticity signal data; The first color gamut data indicating the color gamut of the first printing device is acquired, and the second color gamut data indicating the color gamut of the second printing device is acquired based on the second chromaticity signal data. Color gamut data acquisition means, and the second gamut data existing outside the color gamut indicated by the acquired first gamut data among the acquired second chromaticity signal data. Conversion means for converting outermost chromaticity signal data belonging to the outermost gamut of the color gamut so as to be within the color gamut indicated by the first gamut data; and the first color acquired by the chromaticity signal data acquisition means Interpolating means for interpolating the high chroma region based on the degree signal data and the second chromaticity signal data and the outermost chromaticity signal data converted by the converting means. .

  According to this, a color chart for color gamut compression that does not have a high color saturation area is printed in advance by the second printing apparatus and the first printing apparatus, and the color chart for color gamut compression is measured, thereby obtaining a high color saturation area. The second chromaticity signal data and the first chromaticity signal data that do not exist can be acquired, so that the second chromaticity signal data, the first chromaticity signal data, and the outermost contour after conversion are converted. By interpolating the high saturation region based on the chromaticity signal data, the color gamut changes smoothly in the vicinity of the threshold of the gamut (high saturation region), and the inside of the gamut of the first printing apparatus is changed. In addition, since the entire color gamut can be quickly compressed without being compressed, high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above-mentioned problem, the invention according to claim 3 is the color gamut compression device according to claim 1 or 2, wherein the converting means converts the specific color component of the outermost chromaticity signal data. Weighting is performed so that the color difference between the outermost chromaticity signal data before conversion and after conversion is minimized.

  According to this, for example, it is possible to minimize the influence on human vision by weighting and converting color components that greatly affect human vision.

  In order to solve the above problem, the invention according to claim 4 is the color gamut compression device according to claim 3, wherein the specific color component is one of hue, brightness, or saturation. Features.

  According to this, while maintaining the hue that greatly affects human vision, the ratio of the lightness displacement to the saturation displacement is set to 3 to 1, for example, the lightness that has a relatively large effect on human vision is possible. It is possible to perform compression by weighting so as to maintain, and it is possible to perform color gamut compression in consideration of influence on human vision.

  In order to solve the above problem, the invention according to claim 5 is the color gamut compression device according to any one of claims 1 to 4, wherein the interpolation means is based on linear interpolation or nonlinear interpolation. It is characterized by being.

  According to this, it is possible to realize compression with more certainty and high gradation reproducibility.

  In order to solve the above problem, the invention according to claim 6 is the color gamut compression device according to any one of claims 1 to 5, wherein the high saturation area is included in the first color gamut data. It is a region that is 80% or more of the maximum saturation that can be reproduced at each lightness.

  According to this, the color gamut changes smoothly in the vicinity of the color gamut threshold, and the inside of the color gamut of the printing apparatus as the first device can be reproduced by the first device, such as a value measured by printing a color chart. Therefore, it is possible to compress the entire color gamut by using the same value as it is, so that high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above problem, the invention according to claim 7 is the color gamut compression device according to any one of claims 1 to 6, wherein the color gamut data acquisition means is the chromaticity signal data. Based on the second chromaticity signal data acquired by the acquisition means, second gamut data indicating the gamut of the second device is acquired, and the saturation of the second gamut data is 0 (zero). The difference between the minimum brightness value in the case and the minimum brightness value in the case where the saturation of the first color gamut data is 0 (zero) is greater than or equal to a predetermined value, and the saturation of the second color gamut data When the difference between the maximum value of brightness when the degree is 0 (zero) and the maximum value of brightness when the saturation of the first color gamut data is 0 (zero) is greater than or equal to a predetermined value, The high saturation region is a region where a color difference from the first color gamut data is a predetermined value or more.

  According to this, the color gamut changes smoothly in the vicinity of the color gamut threshold, and the inside of the color gamut of the printing apparatus as the first device can be reproduced by the first device, such as a value measured by printing a color chart. Therefore, it is possible to compress the entire color gamut by using the same value as it is, so that high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above problem, according to an eighth aspect of the present invention, in the color gamut compression device according to the seventh aspect, the high saturation region is a region in which a color difference ΔE with respect to the first color gamut data is 5 or more. It is characterized by being.

  This makes it possible to perform color gamut compression considering the effect on human vision.

  In order to solve the above problem, the invention according to claim 9 is the color gamut compression device according to any one of claims 1 to 8, wherein the color gamut conversion is performed based on an interpolation result by the interpolation means. And a lookup table creating means for creating a lookup table.

  According to this, when creating a lookup table for converting a color gamut between devices such as printing apparatuses having different color gamuts, the color gamut conversion lookup table has higher color conversion accuracy and higher gradation reproducibility. Can be created.

  In order to solve the above-described problem, according to a tenth aspect of the present invention, in the color gamut compression device according to any one of the second to ninth aspects, the color signal is a coordinate value in CIELab space. It is characterized by.

  According to this, by replacing the color chart printed by the first printing apparatus with the color signal as the coordinate value in the CIELab space, it is possible to replace the color chart with an optimum device-independent color space.

  In order to solve the above-mentioned problem, the invention according to claim 11 is to set the color gamut of the second device when the color gamut of the first device is smaller than the target color gamut of the second device. A computer included in a color gamut compression device that compresses a plurality of first chromaticity signal data indicating a chromaticity signal related to the first device and a plurality of first chromaticity signals related to the second device. Chromaticity signal data acquisition means for acquiring second chromaticity signal data, acquiring first gamut data indicating a gamut of a first device based on the first chromaticity signal data, and Gamut data acquisition means for acquiring second gamut data indicating the gamut of the second device based on the chromaticity signal data of the second device, and the first gamut of the second chromaticity signal data A second existing in the color gamut of the first device indicated by the data The second chromaticity signal data belonging to the high chroma region including the chromaticity signal data, and the other chromaticity signal data excluding the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second gamut data. Removing means for removing the second chromaticity signal data and the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data within the color gamut indicated by the first color gamut data Conversion means for converting to fit, the first chromaticity signal data acquired by the chromaticity signal data acquisition means, the remaining second chromaticity signal data after removal by the removal means, and the conversion means Based on the converted outermost chromaticity signal data, it functions as an interpolating means for interpolating the high chroma region.

  According to this, among the second chromaticity signal data that can be reproduced by the second device, the second chromaticity signal data belonging to the high saturation region, and other than the outermost chromaticity signal data, The chromaticity signal data of 2 is removed, the outermost chromaticity signal data is converted to be within the color gamut of the first device, and the converted outermost chromaticity signal data and the second color remaining without being removed are converted. Since the high saturation area is interpolated based on the degree signal data and the acquired first chromaticity signal data, the area changes smoothly near the threshold of the color gamut (high saturation area), and the first The entire color gamut can be quickly compressed without changing the inside of the device gamut, realizing high color conversion accuracy and high gradation reproducibility before and after gamut compression. It becomes possible to do.

  In order to solve the above-described problem, the invention according to claim 12 is directed to the second printing apparatus when the color gamut of the first printing apparatus is smaller than the target color gamut of the second printing apparatus. A computer included in a color gamut compression device that compresses a color gamut is a color chart for color gamut compression printed by the first printing device and the second printing device, the color of the second printing device. Measuring the color gamut compression color chart in which there is no color data in a high saturation region other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second color gamut data indicating the color gamut, Chromaticity for acquiring a plurality of color signals related to one printing apparatus and the second printing apparatus, and acquiring second chromaticity signal data and first chromaticity signal data based on the respective color signals Signal data acquisition means, said first color The first color gamut data indicating the color gamut of the first printing apparatus is acquired based on the signal data, and the second color indicating the color gamut of the second printing apparatus based on the second chromaticity signal data. Gamut data acquisition means for acquiring gamut data; and the second gamut existing outside the gamut indicated by the acquired first gamut data among the acquired second chromaticity signal data The outermost chromaticity signal data belonging to the outermost gamut of the color gamut indicated by the data is converted by the conversion means so as to be within the color gamut indicated by the first gamut data, and acquired by the chromaticity signal data acquisition means Based on the first chromaticity signal data and the second chromaticity signal data, and the outermost chromaticity signal data converted by the conversion means, functioning as an interpolation means for interpolating the high chroma region. Features.

  According to this, a color chart for color gamut compression that does not have a high color saturation area is printed in advance by the second printing apparatus and the first printing apparatus, and the color chart for color gamut compression is measured, thereby obtaining a high color saturation area. The second chromaticity signal data and the first chromaticity signal data that do not exist can be acquired, so that the second chromaticity signal data, the first chromaticity signal data, and the outermost contour after conversion are converted. By interpolating the high saturation region based on the chromaticity signal data, the color gamut changes smoothly in the vicinity of the threshold of the gamut (high saturation region), and the inside of the gamut of the first printing apparatus is changed. In addition, since the entire color gamut can be quickly compressed without being compressed, high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above-mentioned problem, the invention described in claim 13 is the color gamut compression program according to claim 11 or claim 12, wherein the conversion means is used as a specific color component of the outermost chromaticity signal data. Weighting is performed so that the conversion is performed so that the color difference between the outermost chromaticity signal data before conversion and after conversion is minimized.

  According to this, for example, it is possible to minimize the influence on human vision by weighting and converting color components that greatly affect human vision.

  In order to solve the above-described problem, the invention according to claim 14 is the color gamut compression program according to claim 13, wherein the specific color component is one of hue, brightness, or saturation. Features.

  According to this, while maintaining the hue that greatly affects human vision, the ratio of the lightness displacement to the saturation displacement is set to 3 to 1, for example, the lightness that has a relatively large effect on human vision is possible. It is possible to perform compression by weighting so as to maintain, and it is possible to perform color gamut compression in consideration of influence on human vision.

  In order to solve the above-mentioned problem, according to a fifteenth aspect of the present invention, in the color gamut compression program according to any one of the eleventh to fourteenth aspects, the interpolation means is based on linear interpolation or non-linear interpolation. It is characterized by being.

  According to this, it is possible to realize compression with more certainty and high gradation reproducibility.

  In order to solve the above-described problem, the invention described in claim 16 is the color gamut compression program according to any one of claims 11 to 15, wherein the high saturation area is included in the first color gamut data. It is a region that is 80% or more of the maximum saturation that can be reproduced at each lightness.

  According to this, the color gamut changes smoothly in the vicinity of the color gamut threshold, and the inside of the color gamut of the printing apparatus as the first device can be reproduced by the first device, such as a value measured by printing a color chart. Therefore, it is possible to compress the entire color gamut by using the same value as it is, so that high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above-described problem, the invention according to claim 17 is the color gamut compression program according to any one of claims 11 to 16, wherein the saturation of the second color gamut data is 0 ( The difference between the minimum brightness value in the case of zero) and the minimum brightness value in the case where the saturation of the first color gamut data is 0 (zero), and the second color gamut The difference between the maximum brightness value when the data saturation is 0 (zero) and the maximum brightness value when the saturation of the first color gamut data is 0 (zero) is greater than or equal to a predetermined value. The high saturation region is a region where a color difference from the first color gamut data is a predetermined value or more.

  According to this, the color gamut changes smoothly in the vicinity of the color gamut threshold, and the inside of the color gamut of the printing apparatus as the first device can be reproduced by the first device, such as a value measured by printing a color chart. Therefore, it is possible to compress the entire color gamut by using the same value as it is, so that high color conversion accuracy and high gradation reproducibility can be realized before and after color gamut compression.

  In order to solve the above problem, according to an eighteenth aspect of the present invention, in the color gamut compression program according to the seventeenth aspect, the high saturation region is a region in which a color difference ΔE with respect to the first color gamut data is 5 or more. It is characterized by being.

  This makes it possible to perform color gamut compression considering the effect on human vision.

  In order to solve the above-mentioned problem, the invention described in claim 19 is the color gamut compression program according to any one of claims 11 to 18, wherein the computer is based on an interpolation result by the interpolation means. The color gamut conversion lookup table is further functioned as lookup table creation means for creating a color gamut conversion lookup table.

  According to this, when creating a lookup table for converting a color gamut between devices such as printing apparatuses having different color gamuts, the color gamut conversion lookup table has higher color conversion accuracy and higher gradation reproducibility. Can be created.

  In order to solve the above problem, the invention described in claim 20 is the color gamut compression program described in claims 12-19, wherein the color signal is a coordinate value in CIELab space.

  According to this, by replacing the color chart printed by the first printing apparatus with the color signal as the coordinate value in the CIELab space, it is possible to replace the color chart with an optimum device-independent color space.

  In order to solve the above problem, the invention according to claim 21 is characterized in that the color conversion program according to any one of claims 11 to 20 is stored so as to be readable by a computer. .

  In order to solve the above-described problem, the invention according to claim 22 is directed to the second device color gamut when the color gamut of the first device is smaller than the target color gamut of the second device. A gamut compression method for compressing a plurality of first chromaticity signal data indicating a chromaticity signal related to the first device and a plurality of second chromaticity signals indicating a chromaticity signal related to the second device. Obtaining chromaticity signal data; obtaining first gamut data indicating a gamut of a first device based on the first chromaticity signal data; and obtaining the second chromaticity signal data. Obtaining the second color gamut data indicating the color gamut of the second device based on the first gamut data, and the first device indicated by the first color gamut data among the second chromaticity signal data The second belonging to the high saturation region including the second chromaticity signal data existing in the color gamut of Removing the second chromaticity signal data other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second gamut data, which is chromaticity signal data; A conversion step of converting the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data so as to be within the color gamut indicated by the first color gamut data; An interpolation step for interpolating the high saturation region based on the chromaticity signal data of the image, the remaining second chromaticity signal data after the removal, and the outermost chromaticity signal data after the conversion, It is characterized by having.

  In order to solve the above-described problem, the invention according to claim 23 is directed to the second printing apparatus when the color gamut of the first printing apparatus is smaller than the target color gamut of the second printing apparatus. A color gamut compression method for compressing a color gamut, a color gamut compression color chart printed by the first printing device and the second printing device, wherein the color gamut of the second printing device is The color chart for color gamut compression in which there is no color data in a high saturation area other than the outermost chromaticity signal data belonging to the outermost area of the color gamut indicated by the second color gamut data shown, Acquiring a plurality of color signals relating to the printing device and the second printing device, respectively, obtaining second chromaticity signal data and first chromaticity signal data based on the respective color signals; and First printing based on the first chromaticity signal data Obtaining first color gamut data indicating the color gamut of the second printing device and obtaining second color gamut data indicating the color gamut of the second printing device based on the second chromaticity signal data; and Out of the acquired second chromaticity signal data, the outermost contour belonging to the outermost contour of the color gamut indicated by the second color gamut data existing outside the color gamut indicated by the acquired first color gamut data. A conversion step of converting chromaticity signal data so as to be within the color gamut indicated by the first color gamut data; the acquired first chromaticity signal data and second chromaticity signal data; and the conversion And an interpolation step for interpolating the high saturation region based on the later outermost chromaticity signal data.

  In order to solve the above problem, according to a twenty-fourth aspect of the present invention, in the color gamut compression method according to the twenty-second or twenty-third aspect, the converting step converts a specific color component of the outermost chromaticity signal data. Weighting is performed so that the color difference between the outermost chromaticity signal data before conversion and after conversion is minimized.

  In order to solve the above-mentioned problem, the invention according to claim 25 is the color gamut compression method according to claim 24, wherein the specific color component is one of hue, brightness, or saturation. Features.

  In order to solve the above-mentioned problem, according to a twenty-sixth aspect of the present invention, in the color gamut compression method according to any one of the twenty-second to twenty-fifth aspects, the interpolation step is performed by linear interpolation or non-linear interpolation. It is characterized by being.

  In order to solve the above-mentioned problem, according to a twenty-seventh aspect of the present invention, in the color gamut compression method according to any one of the twenty-second to twenty-sixth aspects, the high saturation region is the first color gamut data. It is a region that is 80% or more of the maximum saturation that can be reproduced at each lightness.

  In order to solve the above problem, the invention described in claim 28 is the color gamut compression method according to any one of claims 22 to 27, wherein the saturation of the second color gamut data is 0 ( The difference between the minimum brightness value in the case of zero) and the minimum brightness value in the case where the saturation of the first color gamut data is 0 (zero), and the second color gamut The difference between the maximum brightness value when the data saturation is 0 (zero) and the maximum brightness value when the saturation of the first color gamut data is 0 (zero) is greater than or equal to a predetermined value. The high saturation region is a region where a color difference from the first color gamut data is a predetermined value or more.

  In order to solve the above problem, according to a twenty-ninth aspect of the present invention, in the color gamut compression method according to the twenty-eighth aspect, the high saturation region is a region where a color difference ΔE from the first color gamut data is 5 or more. It is characterized by being.

  In order to solve the above problem, the invention described in claim 30 is the color gamut compression method according to any one of claims 22 to 29, wherein the color gamut conversion is performed based on the interpolation result of the interpolation step. And a step of creating a look-up table.

  In order to solve the above-mentioned problem, the invention described in claim 31 is the color gamut compression method according to any one of claims 23 to 29, wherein the color signal is a coordinate value in CIELab space. It is characterized by.

  According to the present invention, among the second chromaticity signal data that can be reproduced by the second device, the second chromaticity signal data belonging to the high saturation region, and other than the outermost chromaticity signal data, The second chromaticity signal data is removed, and the outermost chromaticity signal data is converted so as to be within the color gamut of the first device, and the converted outermost chromaticity signal data and the second chromaticity signal data remaining without being removed are converted. Since the high saturation area is interpolated based on the chromaticity signal data and the acquired first chromaticity signal data, the color changes smoothly near the threshold of the color gamut (high saturation area), and the first The entire color gamut can be quickly compressed without changing the inside of the device's color gamut, so high color conversion accuracy and high gradation reproducibility can be achieved before and after color gamut compression. Can be realized.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In this embodiment, color reproduction of color printing by a printing main machine as an example of a large-sized business printing apparatus such as an offset printing apparatus is smaller than other printing apparatuses having different color gamuts, for example, a printing main machine. An example in which the present invention is applied to a color gamut compression apparatus that can be reproduced by an inkjet printer as a general-purpose small-sized printing apparatus will be described.

[Configuration and function of color gamut compression device]
First, the configuration and function of the color gamut compression device according to the present embodiment will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating a schematic configuration example of a color gamut compression device according to the present embodiment, and FIG. 2 is an explanatory diagram of color gamut compression processing according to the present embodiment.

  As shown in FIG. 1, the color gamut compression device 1 includes a storage unit 11 including an HDD (Hard Disc Drive) that stores (stores) various data, tables, programs, and the like, a liquid crystal display monitor, and the like. Display unit 12, printing device Po (second device) that is a target of color reproduction, inkjet printer Pi (first device), and external device connection unit 13 for connecting with spectrocolorimeter X, calculation function It has a CPU (Central Processing Unit), a working RAM (Random-Access Memory), an arithmetic control unit 14 as a computer, which is composed of a ROM (Read-Only Memory) that stores various data and programs, and the like. These components are connected to each other via a bus 15.

  The storage unit 11 associates the device signal Dd (coordinate value in the device-specific CMYK color space) of each device with the color signal Dc (coordinate value in the device-independent color space) that can reproduce the device signal Dd. In addition, it is stored as a color conversion table. In the present embodiment, as shown in FIG. 2, IT8.7 /, which is standardized by ISO (International Organization for Standardization) 12642, respectively, in the printing main unit Po and the inkjet printer Pi as devices. A color chart composed of CMYK such as 3 is printed (output) (see FIG. 2A), and the color chart is measured by the spectrocolorimeter X (see FIG. 2B). The color signal Dc corresponding to each device signal Dd constituting the color chart is acquired, and the color conversion table To of the printing apparatus Po and the color conversion table Ti of the ink jet printer Pi are respectively created and stored in the storage unit 11. (See FIG. 2C).

  In other words, the color conversion table To and the color conversion table Ti, as shown in FIG. 3, represent the device-specific color information (device signal Dd) of the printing machine Po and the ink jet printer Pi as a common color space (international illumination). The 1976 CIELab space, etc. (color signal Dc) determined by the committee (CIE). In this way, by replacing the device-specific color information with a common color space that does not depend on the device, even if the color gamut of the inkjet printer Pi is smaller than the color gamut of the printing machine Po, printing can be performed. It is possible to perform color gamut compression (Gamut Compression) processing for clipping a color outside the color gamut to the color gamut of the inkjet printer Pi while maintaining the color information in the printer Po as much as possible. Note that the color gamut compression process will be described together with the description of the color gamut conversion lookup table creation process described in detail later.

  Further, the color chart printed by the printing apparatus Po and the ink jet printer Pi has coordinate values in CMYK color space specific to each device, C (cyan: 0 ≦ C ≦ 255), M (magenta: 0 ≦ M ≦ 255). , Y (yellow: 0 ≦ Y ≦ 255), and K (black: 0 ≦ K ≦ 255). The color chart is stored in the storage unit 11 in advance, for example. By operating an operation input unit (not shown) or the like, the color chart is printed from the printing machine Po and the inkjet printer Pi via the external device connection unit 13, and measured by the spectrocolorimeter X. The created color conversion table To and color conversion table Ti are created and stored in the storage unit 11 as shown in FIG.

  Since C, M, Y, and K each have one of values from 0 to 255, it is difficult and cumbersome to measure all these combinations with a spectrocolorimeter or the like. Therefore, in practice, for example, C (cyan), M (magenta), Y (yellow), and K (black), each of 6 steps (0%, 20%, 40%, 60%, 80%, 100%) ) For a total of 3125 device signals Dd, the corresponding color signals Dc (that is, the device signals Dd can be reproduced) are acquired to obtain the color conversion table To and the color conversion table Ti. In this case, the obtained CMYK values may be interpolated to obtain a desired number of device signals Dd and color signals Dc corresponding to the device signals Dd. As the number of combinations of the device signal Dd and the color signal Dc increases, the accuracy of the color gamut conversion lookup table created in the color gamut conversion lookup table creation process described in detail later improves.

  The display unit 12 operates a color input signal Dc desired to be displayed by a user operating an operation input unit configured with a mouse or the like (not shown) among the color signals Dc included in the color conversion table To and the color conversion table Ti. When is selected, a color based on the selected color signal Dc is displayed. Further, based on the various processing signals from the arithmetic control unit 14, the display instructed by the processing signals is performed.

  The external device connection unit 13 is for connecting to the spectrocolorimeter X, the printing machine Po, and the ink jet printer Pi.

  The arithmetic control unit 14 includes a CPU (Central Processing Unit) (not shown), a working RAM (Random Access Memory), a ROM (Read Only Memory) that stores various control programs and data including the color conversion program of the present invention, and an oscillation. In order to control each of the above components to realize an operation corresponding to operation information included in the operation signal based on an operation signal from an operation input unit (not shown). Control information is generated, and the control information is output to the corresponding constituent member via the bus 15 to control the operation of each constituent member. Further, the arithmetic control unit 14 executes a program stored in a ROM or the like, thereby creating a chromaticity signal data acquisition unit, a color gamut data acquisition unit, a removal unit, a conversion unit, an interpolation unit, and a lookup table according to the present invention. It is designed to function as a means.

  First, the calculation control unit 14 functions as a chromaticity signal data acquisition unit, and stores a color signal Dc reproducible by the ink jet printer Pi and a color signal Dc reproducible by the printing apparatus Po in the storage unit 11. The first chromaticity signal data and the second chromaticity signal data indicating the chromaticity signal are acquired based on the respective color signals Dc, respectively, with reference to Ti and To.

  The arithmetic control unit 14 functions as color gamut data acquisition means, acquires color gamut data indicating the color gamut of the inkjet printer Pi based on the chromaticity signal data of the inkjet printer Pi, and acquires the chromaticity of the printing apparatus Po. Color gamut data indicating the color gamut of the printing apparatus Po is acquired based on the signal data. The color gamut data will be described in detail in the description of the color gamut conversion lookup table creation process.

  Further, the arithmetic control unit 14 functions as a removing unit, and is chromaticity signal data belonging to a high saturation area including chromaticity signal data existing in the color gamut of the inkjet printer Pi among the chromaticity signal data of the printing apparatus Po. Therefore, the chromaticity signal data other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut of the printing apparatus Po is removed. Note that the method of removing the outermost chromaticity signal data will also be described in detail in the description of the color gamut conversion lookup table creation process.

  Further, the arithmetic control unit 14 functions as a conversion unit, and converts the outermost chromaticity signal data existing outside the color gamut of the inkjet printer Pi so as to be within the color gamut of the inkjet printer Pi.

  The arithmetic control unit 14 functions as an interpolation unit, and the chromaticity signal data of the ink jet printer Pi, the chromaticity signal data of the remaining printing machine Po after the removal, and the outermost chromaticity signal after the conversion. And interpolating the high saturation region based on the data.

  In addition, the arithmetic control unit 14 functions as a lookup table creation unit, and creates a color gamut conversion lookup table between the printing apparatus Po and the inkjet printer Pi based on the interpolation result obtained by interpolating the high saturation area.

  Note that further specific processing in the arithmetic control unit 14 will be described in detail in the following description of the color gamut conversion table creation processing.

[Lookup table creation processing for color gamut conversion]
Next, a specific method of color gamut conversion lookup table creation processing will be described with reference to FIGS. In the color gamut conversion lookup table creation process, the color gamut compression (Gamut Compression) is performed to compress the color gamut of the printing machine Po in the CIE / L ^* C ^* h color space into the color gamut of the inkjet printer Pi. The method will be described in detail. Here, the CIE / L ^* C ^* h color space means lightness (lightness: L ^* ) representing the brightness of the color, which is perception of human colors, and chroma (chroma: C ^* ) representing the vividness of the color. A color space based on three attributes of hue (hue: h) representing a color system is shown, and these three attributes can be handled as independent color components (parameters). As will be described below, it is easy to perceive that gamut compression is performed in the CIE / L ^* C ^* h color space. Generally, the hue (h) is constant and the lightness (L ^* ) And saturation (C ^* ) are preferably performed on a two-dimensional plane.

  FIG. 4 is a flowchart showing the color gamut conversion lookup table creation processing in the arithmetic control unit 14, and the processing shown in the flowchart is a program (stored in advance in a ROM or the like (not shown) in the arithmetic control unit 14. (Including a color gamut compression program)) based on the control of the arithmetic control unit 14.

  The process shown in FIG. 4 is a color gamut conversion lookup table in which the user of the color gamut compression device 1 operates an operation input unit or the like (not shown) to compress the color gamut of the printing apparatus Po into the color gamut of the inkjet printer Pi. The process starts when an LUT creation is instructed.

  First, the color signal Dc is acquired with reference to the color conversion table To stored in the storage unit 11 (step S1).

Next, based on each acquired color signal Dc, chromaticity signal data Df as second chromaticity signal data indicating lightness (L ^* ) and saturation (C ^* ) as chromaticity signals is calculated. (Step S2). According to the example shown in FIG. 2C, m chromaticity signal data Df are calculated and acquired from m color signals Dc.

Next, referring to the color conversion table Ti stored in the storage unit 11, based on each color signal Dc stored in the color conversion table Ti, brightness (L *) and saturation (C ^* ) As a first color gamut data indicating a color range (color gamut) that can be reproduced by the inkjet printer Pi on a two-dimensional plane (hereinafter referred to as an L ^* -C ^* plane). The area data Ri is calculated (acquired) (step S3).

In FIG. 5, the chromaticity signal data Df of the m number of printing machines Po acquired in step S2 and the gamut data Ri of the ink jet printer Pi acquired in step S3 are represented by lightness (L ^* ) and saturation (C ^* ) L ^* -C ^* coordinates plotted on the L ^* -C ^* plane.

In FIG. 5, black circles indicate chromaticity signal data Df applied to the printing main unit Po, and solid line curves indicate color gamut data Ri indicating the color gamut of the inkjet printer Pi. Note that the color gamut of the inkjet printer Pi has a saturation (C ^* ) from 0 (zero) to a value on the solid line curve indicating the color gamut data Ri, that is, the color gamut data Ri at each lightness (L ^* ). Is a region surrounded by a solid curve indicating L ^* and the L ^* axis. The color gamut data Ri is acquired to each of the chromaticity signal data based on the chrominance signal Dc acquired with reference to the color conversion table Ti, and the gamut signal data is shown to the extent that the outline of the gamut is clearly indicated. By performing the interpolation operation, the outline of the color gamut specified on the L ^* -C ^* plane is finally used as the color gamut data Ri indicating the color gamut of the inkjet printer Pi.

Then, among the m chromaticity signal data Df acquired in step S2, each luminosity of the chromaticity signal data Df having saturation (C ^* ) near the threshold of the color gamut, that is, the color gamut data Ri indicated by the solid curve. The chromaticity signal data Df belonging to the high saturation region having a value of 80% or more of the maximum saturation (C ^* ) reproducible in (L ^* ) is selected (step S4).

Subsequently, of the chromaticity signal data Df selected in step S4, color gamut data as second color gamut data indicating a color range (color gamut) that can be reproduced by the printing apparatus Po. Based on Ro, the chromaticity signal data Df other than the outermost chromaticity signal data Df ′ are removed (removed) (step S5). The chromaticity signal data Df having the highest saturation (C ^* ) at each lightness (L ^* ) is the outermost chromaticity signal data Df ′ belonging to the outermost gamut of the gamut indicated by the gamut data Ro. .

According to the example shown in FIG. 6, the curve indicated by the broken line is the 80% threshold line of the maximum saturation (color gamut data Ri indicated by the solid curve) that can be reproduced at each lightness (L ^* ), and the color indicated by the white circle The chromaticity signal data Df indicates the chromaticity signal data Df belonging to the high saturation region removed in step S5. As an example, as shown in the figure, when the chromaticity signal data Dfa and the chromaticity signal data Dfb are compared, the chromaticity signal data including the highest saturation (C ^* ) in the lightness L1 ^* is the chromaticity signal data. Since it is Dfb, the chromaticity signal data Dfb is the outermost chromaticity signal data Df ′. Similarly, when the chromaticity signal data Dfc and the chromaticity signal data Dfd are compared, the chromaticity signal data including the highest saturation (C ^* ) in the lightness L2 ^* is the chromaticity signal data Dfd. The chromaticity signal data Dfd becomes the outermost chromaticity signal data Df ′.

As described above, in step S5, colors other than the outermost chromaticity signal data Df ′ having the highest saturation (C ^* ) at each lightness (L ^* ) among the chromaticity signal data Df belonging to the high saturation region are excluded. All the degree signal data Df are removed.

  Subsequently, the outermost chromaticity signal data Df ′ existing outside the color gamut of the ink jet printer Pi is clipped (converted) into the color gamut of the ink jet printer Pi indicated by the color gamut data Ri (step S6) (see FIG. 7). At this time, it is desirable to perform conversion so that the color difference between the outermost chromaticity signal data Df ′ before and after conversion is minimized.

Further, as shown in FIG. 7, before clipping, the chromaticity signal data belonging to the high saturation area is removed by the process of step S5 and hardly exists. Therefore, the outermost chromaticity signal data Df ′ is out of the color gamut of the inkjet printer Pi. The conversion (clipping) from to the color gamut only shortens the data interval. That is, as shown in FIG. 8, the chromaticity signal data Df belonging to the high saturation area that can be reproduced by the printing apparatus Po in the process of step S5, except the outermost chromaticity signal data Df ′, When the signal data Df (indicated by a white circle in the figure) is removed, the saturation (C ^* ) of the remaining chromaticity signal data Df (indicated by a black circle in the figure) is the ink jet printer Pi as indicated by the broken line in the figure. A smooth change is shown near the threshold of the color gamut (high saturation region). Since the entire color gamut can be compressed without changing the inside of the color gamut of the ink jet printer Pi that is not near the color gamut threshold (high saturation area), high color conversion accuracy before and after color gamut compression is achieved. High gradation reproducibility can be realized.

Next, since the chromaticity signal data Df belonging to the high saturation area has been removed in the process of step S5, the highest saturation area after clipping is obtained in order to obtain the high saturation area data indicated by the broken line in FIG. 8 by interpolation. Based on the outline chromaticity signal data Df ′, the chromaticity signal data Df remaining without being removed in step S5, and the chromaticity signal data Df stored in the color conversion table Ti, an operation by multiple regression interpolation is performed. For example, a forward look-up table (CMYK → L ^* a ^* b ^* ) of k steps is created (step S7). The forward lookup table (CMYK → L ^* a ^* b ^* ) created in this way is temporarily stored in a RAM (not shown) of the arithmetic control unit 14. Note that the interpolation method in step S7 may be a non-linear interpolation calculation using a neural network or the like, or may be linear interpolation.

Next, based on each color signal Dc (L ^* a ^* b ^* ) of the forward lookup table created in step S7, the device signal Dd ( CMYK) is calculated, and a color gamut conversion lookup table LUT (CMYK → CMYK) between the printing main unit Po and the inkjet printer Pi is created (step S8).

  FIG. 9 shows an example of the color gamut conversion lookup table LUT created in step S8. Normally, the device signal Dd is a four-dimensional color signal expressed in CMYK such as IT8.7 / 3 standardized by ISO12642 as described above. Therefore, this color signal is derived from the three-dimensional color signal. If CMYK is to be obtained, there are a plurality of color signals CMYK corresponding to the three-dimensional color signal Dc. In step S8 in the present embodiment, one color signal that can be reproduced by the inkjet printer Pi is obtained as the device signal Dd from among the plurality of color signals CMYK corresponding to the color signal Dc.

  As described above, according to the color gamut compression device 1 in the present embodiment, the chromaticity signal data Df that belongs to the high saturation area among the chromaticity signal data Df that can be reproduced by the printing apparatus Po, and is the outermost contour. The chromaticity signal data Df other than the chromaticity signal data Df ′ is removed, the outermost chromaticity signal data Df ′ is clipped (converted) so as to be within the color gamut of the inkjet printer Pi, and the outermost contour after clipping (converted). A gamut conversion look based on the chromaticity signal data, the chromaticity signal data Df remaining without being removed, and the chromaticity signal data Df obtained by printing (outputting) the color table with the inkjet printer Pi. Since the uptable LUT is created, the color changes smoothly in the vicinity of the color gamut threshold (high saturation area), and the color gamut of the inkjet printer Pi is colored. Since the entire color gamut can be compressed using the values measured by printing the chart as they are, high color conversion accuracy and high gradation reproducibility can be achieved before and after color gamut compression. It becomes possible.

When clipping the outermost chromaticity signal data Df ′ into the color gamut of the inkjet printer Pi in step S6, a specific color such as lightness (L ^* ), saturation (C ^* ), or hue (H) is used. Clipping so that the color difference ΔE between the outermost chromaticity signal data Df ′ before movement and the outermost chromaticity signal data Df ′ after movement is minimized while maintaining the components or weighting specific color components Thus, the color gamut may be compressed. For example, while maintaining the hue (H) that greatly affects human vision, the ratio of lightness (L ^* ) displacement to saturation (C ^* ) displacement is 3 to 1, and compared with human vision. It is configured to perform weighting and compression so as to maintain the lightness (L ^* ) having a large influence as much as possible. FIG. 10 shows an example in which the outermost chromaticity signal data Df ′ is clipped by weighting the lightness (L ^* ). With this configuration, it is possible to minimize the influence on human vision.

In step S4, the high saturation area is set to 80% or more of the saturation (C ^* ) of the color gamut data Ri of the inkjet printer Pi. However, the present invention is not limited to this. For example, as shown in FIG. a minimum brightness and L ^* (low_i), which is the difference [Delta] L ^*, and / or maximum brightness of the color gamut of an inkjet printer Pi of L ^* and (low_o) is a minimum brightness of the color gamut of printing the machine Po L of ^{* When} the difference ΔL ^* between (Hi_i) and L ^* (Hi_o), which is the maximum brightness of the color gamut of the printing apparatus Po, is equal to or greater than a predetermined value, the difference between the color gamut data Ri of the inkjet printer Pi and A range having a saturation (C ^* ) in which the color difference ΔEa is equal to or greater than a predetermined value is desirably used as the high saturation region.

More specifically, a range having a saturation (C ^* ) in which the color difference ΔEa from the color gamut data Ri of the inkjet printer Pi is equal to or greater than a predetermined value (for example, ΔEa is equal to or greater than 5), that is, indicated by a chain line curve in FIG. A range from the color difference limit line to the color gamut data Ri of the ink jet printer Pi is configured as a high saturation area. The reason why the color difference ΔEa is set to 5 as an example of the predetermined value is that if a difference of about 5 occurs in the color difference, the human vision is surely affected. It should be noted that the color gamut of the printing machine Po is from the saturation (C ^* ) from 0 (zero) to the value on the one-dot chain line curve indicating the gamut data Ro at each lightness (L ^* ), that is, the gamut data. The region is surrounded by a one-dot chain line curve indicating Ro and the L ^* axis. The color gamut data Ro is similar to the color gamut data Ri of the inkjet printer Pi, so that the outline of the color gamut is clearly shown in the m pieces of chromaticity signal data Df acquired with reference to the color conversion table To. By performing the interpolation calculation, the outline of the color gamut specified on the L ^* -C ^* plane is finally used as the color gamut data Ro.

  Further, in the above-described embodiment, the color signal Dc (color conversion shown in FIG. 2C) that can be reproduced by the ink-jet printer Pi is performed by outputting the specified color chart stored in the storage unit 11. The chromaticity signal data Df related to the ink jet printer Pi is acquired based on the table Ti), and the print book based on the color signal Dc (color conversion table To shown in FIG. 2C) that can be reproduced by the printing book machine Po. The color conversion table To and the color conversion table having the color signal Dc for which the color conversion table To and the color conversion table Ti cannot acquire the color signal Df in the high saturation region in advance are obtained. Ti may also be used.

  That is, as shown in FIG. 12, 4 steps (0%, 20%, 40%, 60%, 100%) for each color of C (cyan), M (magenta), and Y (yellow) and 5 for K (black). A color chart for color gamut compression, which is a combination of steps (0%, 25%, 50%, 75%, 100%), is printed as the second printing device Po and the inkjet printer Pi as the first printing device. To output. As described above, the color gamut conversion lookup table described above is obtained by using a color chart that does not have “80%” steps of C (cyan), M (magenta), and Y (yellow), which are high-saturation regions in advance. The processes in steps S4 and S5 in the creation process are not necessary. In this case, the chromaticity signal data Df obtained based on the color signal Dc obtained by measuring the steps of “100%” of C (cyan), M (magenta), and Y (yellow) is the outermost color. Degree signal data Df ′.

  In the above embodiment, coordinate values in the 1976 CIELab space determined by the International Commission on Illumination (CIE) are used as the color signals. It may be a value or a coordinate value in the RGB space.

It is a block diagram which shows the example of a schematic structure of the color gamut compression apparatus concerning this embodiment. It is explanatory drawing of the color gamut compression process concerning this embodiment. It is a conceptual explanatory diagram of color gamut conversion. 5 is a flowchart showing a color gamut conversion lookup table creation process in an arithmetic control unit 14; This is an L ^* -C ^* coordinate plotting the chromaticity signal data Df of the printing machine Po and the gamut data Ri of the ink jet printer Pi. It is explanatory drawing of the high chroma area | region and outermost chromaticity signal data Df 'in the L ^* -C ^* coordinate which plotted the chromaticity signal data Df of this printing apparatus Po, and the gamut data Ri of the inkjet printer Pi. It is explanatory drawing of clipping of the outermost chromaticity signal data Df 'into the color gamut of the inkjet printer Pi. It is explanatory drawing of the chromaticity signal data Df which belongs to the high saturation area | region before and after interpolation. It is an example of the created color gamut conversion lookup table LUT. It is an example of clipping of outermost chromaticity signal data Df ′ into the color gamut of the inkjet printer Pi when weighted. It is explanatory drawing which shows the other determination method about a high saturation area | region. It is explanatory drawing of the color chart for color gamut compression.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color gamut compression apparatus 11 Memory | storage part 12 Display part 13 External apparatus connection part 14 Operation control part 15 Bus Po Printing this machine Pi Inkjet printer X Spectral colorimeter Ti, To Color conversion table L ^* Lightness C ^* Saturation H Hue C Cyan M Magenta Y Yellow K Black Dd Device signal Dc Color signal Df Chromaticity signal data Df 'Outermost chromaticity signal data Ri Color gamut data Ro of inkjet printer Pi Color gamut data ΔEa of printing machine Po Color difference

Claims (31)

A color gamut compression device that compresses the color gamut of the second device when the color gamut of the first device is smaller than the target color gamut of the second device,
Colors for obtaining a plurality of first chromaticity signal data indicating the chromaticity signal related to the first device and a plurality of second chromaticity signal data indicating the chromaticity signal related to the second device. Degree signal data acquisition means,
First gamut data indicating a color gamut of the first device is acquired based on the first chromaticity signal data, and a color gamut of the second device is indicated based on the second chromaticity signal data. Gamut data acquisition means for acquiring second gamut data;
Of the second chromaticity signal data, the second chromaticity belonging to the high chroma region including the second chromaticity signal data existing in the gamut of the first device indicated by the first gamut data. Removing means for removing the second chromaticity signal data other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second gamut data, which is signal data;
Conversion means for converting the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data so as to be within the color gamut indicated by the first color gamut data;
The first chromaticity signal data acquired by the chromaticity signal data acquisition means, the remaining second chromaticity signal data after removal by the removal means, and the outermost color converted by the conversion means Interpolation means for interpolating the high saturation region based on the degree signal data;
A color gamut compression device characterized by comprising: A color gamut compression device that compresses the color gamut of the second printing device when the color gamut of the first printing device is smaller than the target color gamut of the second printing device,
A color gamut compression color chart printed by the first printing device and the second printing device, the color gamut indicated by the second color gamut data indicating the color gamut of the second printing device. Color measurement is performed on the color chart for color gamut compression in which there is no color data in the high saturation region other than the outermost chromaticity signal data belonging to the outermost contour, and a plurality of the first printing device and the second printing device are related to each other. Chromaticity signal data acquisition means for acquiring chromaticity signals and acquiring second chromaticity signal data and first chromaticity signal data based on the respective color signals;
First color gamut data indicating a color gamut of the first printing apparatus is acquired based on the first chromaticity signal data, and a color gamut of the second printing apparatus is acquired based on the second chromaticity signal data. Gamut data acquisition means for acquiring second gamut data indicating
Of the acquired second chromaticity signal data, the outermost color belonging to the outermost contour of the color gamut indicated by the second color gamut data existing outside the color gamut indicated by the acquired first color gamut data. Conversion means for converting the outer chromaticity signal data so as to be within the color gamut indicated by the first color gamut data;
Based on the first chromaticity signal data and the second chromaticity signal data acquired by the chromaticity signal data acquisition means, and the outermost chromaticity signal data converted by the conversion means, the high saturation An interpolation means for interpolating the region;
A color gamut compression device characterized by comprising: In the color gamut compression device according to claim 1 or 2,
The converting means weights a specific color component of the outermost chromaticity signal data and performs conversion so that a color difference between the outermost chromaticity signal data before conversion and after conversion is minimized. Color gamut compression device. The gamut compression device according to claim 3.
The color gamut compression device characterized in that the specific color component is one of hue, brightness, or saturation. The color gamut compression device according to any one of claims 1 to 4,
The color gamut compression device characterized in that the interpolation means is based on linear interpolation or nonlinear interpolation. The gamut compression device according to any one of claims 1 to 5,
The color gamut compression device, wherein the high saturation region is a region that is 80% or more of the maximum saturation that can be reproduced at each lightness related to the first color gamut data. In the color gamut compression device according to any one of claims 1 to 6,
The gamut data acquisition unit acquires second gamut data indicating the gamut of the second device based on the second chromaticity signal data acquired by the chromaticity signal data acquisition unit,
The difference between the minimum brightness value when the saturation of the second gamut data is 0 (zero) and the minimum brightness value when the saturation of the first gamut data is 0 (zero) is The maximum brightness when the saturation of the second color gamut data is 0 (zero) or more and the brightness when the saturation of the first color gamut data is 0 (zero) When the difference from the maximum value of the color gamut is equal to or greater than a predetermined value, the high saturation region is a region where the color difference from the first color gamut data is equal to or greater than a predetermined value. The color gamut compression device according to claim 7.
The color gamut compression apparatus, wherein the high saturation region is a region where a color difference ΔE from the first color gamut data is 5 or more. In the color gamut compression device according to any one of claims 1 to 8,
2. A color gamut compression device comprising: a look-up table creating means for creating a color gamut conversion look-up table based on an interpolation result by the interpolation means. The color gamut compression device according to any one of claims 2 to 9,
The color gamut compression device, wherein the color signal is a coordinate value in CIELab space. A computer included in a color gamut compression device that compresses the color gamut of the second device when the color gamut of the first device is smaller than the target color gamut of the second device;
Colors for obtaining a plurality of first chromaticity signal data indicating the chromaticity signal related to the first device and a plurality of second chromaticity signal data indicating the chromaticity signal related to the second device. Degree signal data acquisition means,
First gamut data indicating a color gamut of the first device is acquired based on the first chromaticity signal data, and a color gamut of the second device is indicated based on the second chromaticity signal data. Gamut data acquisition means for acquiring second gamut data;
Of the second chromaticity signal data, the second chromaticity belonging to the high chroma region including the second chromaticity signal data existing in the gamut of the first device indicated by the first gamut data. Removing means for removing the second chromaticity signal data other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second gamut data, which is signal data;
Conversion means for converting the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data so as to be within the color gamut indicated by the first color gamut data;
The first chromaticity signal data acquired by the chromaticity signal data acquisition means, the remaining second chromaticity signal data after removal by the removal means, and the outermost color converted by the conversion means A color gamut compression program that functions as an interpolating means for interpolating the high saturation area based on degree signal data. A computer included in the color gamut compression device that compresses the color gamut of the second printing device when the color gamut of the first printing device is smaller than the target color gamut of the second printing device;
A color gamut compression color chart printed by the first printing device and the second printing device, the color gamut indicated by the second color gamut data indicating the color gamut of the second printing device. Color measurement is performed on the color chart for color gamut compression in which there is no color data in the high saturation region other than the outermost chromaticity signal data belonging to the outermost contour, and a plurality of the first printing device and the second printing device are related to each other. Chromaticity signal data acquisition means for acquiring chromaticity signals and acquiring second chromaticity signal data and first chromaticity signal data based on the respective color signals;
First color gamut data indicating a color gamut of the first printing apparatus is acquired based on the first chromaticity signal data, and a color gamut of the second printing apparatus is acquired based on the second chromaticity signal data. Gamut data acquisition means for acquiring second gamut data indicating
Of the acquired second chromaticity signal data, the outermost color belonging to the outermost contour of the color gamut indicated by the second color gamut data existing outside the color gamut indicated by the acquired first color gamut data. Conversion means for converting the outer chromaticity signal data so as to be within the color gamut indicated by the first color gamut data; and
Based on the first chromaticity signal data and the second chromaticity signal data acquired by the chromaticity signal data acquisition means, and the outermost chromaticity signal data converted by the conversion means, the high saturation A color gamut compression program which functions as an interpolation means for interpolating a region. The color gamut compression program according to claim 11 or 12,
The converting means functions to weight a specific color component of the outermost chromaticity signal data and perform conversion so that a color difference between the outermost chromaticity signal data before conversion and after conversion is minimized. Color gamut compression program characterized by The color gamut compression program according to claim 13,
The color gamut compression program characterized in that the specific color component is one of hue, brightness, or saturation. The color gamut compression program according to any one of claims 11 to 14,
A color gamut compression program characterized in that the interpolation means is based on linear interpolation or nonlinear interpolation. The color gamut compression program according to any one of claims 11 to 15,
The color gamut compression program characterized in that the high saturation area is an area of 80% or more of the maximum saturation that can be reproduced at each lightness related to the first color gamut data. The color gamut compression program according to any one of claims 11 to 16,
The difference between the minimum brightness value when the saturation of the second gamut data is 0 (zero) and the minimum brightness value when the saturation of the first gamut data is 0 (zero) is The maximum brightness when the saturation of the second color gamut data is 0 (zero) or more and the brightness when the saturation of the first color gamut data is 0 (zero) A color gamut compression program characterized in that the high saturation region is a region where the color difference from the first color gamut data is greater than or equal to a predetermined value when the difference from the maximum value is greater than or equal to a predetermined value. The color gamut compression program according to claim 17,
The color gamut compression program, wherein the high saturation area is an area where a color difference ΔE with respect to the first color gamut data is 5 or more. The gamut compression program according to any one of claims 11 to 18, wherein the computer is
A gamut compression program that further functions as lookup table creation means for creating a gamut conversion lookup table based on an interpolation result by the interpolation means. The color gamut compression program according to any one of claims 12 to 19,
The color gamut compression program characterized in that the color signal is a coordinate value in CIELab space.   21. A recording medium in which the color conversion program according to claim 11 is stored so as to be readable by a computer. A color gamut compression method that compresses the color gamut of the second device when the color gamut of the first device is smaller than the target color gamut of the second device,
Obtaining a plurality of first chromaticity signal data indicating a chromaticity signal related to the first device and a plurality of second chromaticity signal data indicating a chromaticity signal related to the second device; When,
First gamut data indicating a color gamut of the first device is acquired based on the first chromaticity signal data, and a color gamut of the second device is indicated based on the second chromaticity signal data. Obtaining second color gamut data;
Of the second chromaticity signal data, the second chromaticity belonging to the high chroma region including the second chromaticity signal data existing in the gamut of the first device indicated by the first gamut data. Removing the second chromaticity signal data other than the outermost chromaticity signal data belonging to the outermost contour of the color gamut indicated by the second gamut data, which is signal data;
A conversion step for converting the outermost chromaticity signal data existing outside the color gamut indicated by the first color gamut data so as to be within the color gamut indicated by the first color gamut data;
Based on the acquired first chromaticity signal data, the remaining second chromaticity signal data after the removal, and the outermost chromaticity signal data after the conversion, the high saturation region is determined. An interpolation process to interpolate;
A color gamut compression method characterized by comprising: A color gamut compression method for compressing the color gamut of the second printing device when the color gamut of the first printing device is smaller than the target color gamut of the second printing device,
A color gamut compression color chart printed by the first printing device and the second printing device, the color gamut indicated by the second color gamut data indicating the color gamut of the second printing device. Color measurement is performed on the color chart for color gamut compression in which there is no color data in the high saturation region other than the outermost chromaticity signal data belonging to the outermost contour, and a plurality of the first printing device and the second printing device are related to each other. Obtaining each chrominance signal and obtaining the second chromaticity signal data and the first chromaticity signal data based on the respective chrominance signals;
First color gamut data indicating a color gamut of the first printing apparatus is acquired based on the first chromaticity signal data, and a color gamut of the second printing apparatus is acquired based on the second chromaticity signal data. Obtaining a second color gamut data indicating:
Of the acquired second chromaticity signal data, the outermost color belonging to the outermost contour of the color gamut indicated by the second color gamut data existing outside the color gamut indicated by the acquired first color gamut data. A conversion step of converting the outline chromaticity signal data so as to be within the color gamut indicated by the first color gamut data;
An interpolation step of interpolating the high saturation region based on the acquired first chromaticity signal data and second chromaticity signal data, and the outermost chromaticity signal data after the conversion;
A color gamut compression method characterized by comprising: The color gamut compression method according to claim 22 or claim 23,
In the converting step, the specific color component of the outermost chromaticity signal data is weighted and converted so that the color difference between the outermost chromaticity signal data before conversion and after conversion is minimized. Color gamut compression method. The color gamut compression method according to claim 24, wherein:
The color gamut compression method, wherein the specific color component is any one of hue, lightness, and saturation. The color gamut compression method according to any one of claims 22 to 25,
The color gamut compression method, wherein the interpolation step is performed by linear interpolation or nonlinear interpolation. The color gamut compression method according to any one of claims 22 to 26,
The color gamut compression method, wherein the high saturation region is a region of 80% or more of the maximum saturation that can be reproduced at each lightness related to the first color gamut data. The color gamut compression method according to any one of claims 22 to 27,
The difference between the minimum brightness value when the saturation of the second gamut data is 0 (zero) and the minimum brightness value when the saturation of the first gamut data is 0 (zero) is The maximum brightness when the saturation of the second color gamut data is 0 (zero) or more and the brightness when the saturation of the first color gamut data is 0 (zero) The color gamut compression method is characterized in that, when the difference from the maximum value is equal to or greater than a predetermined value, the high saturation region is a region where the color difference from the first color gamut data is equal to or greater than a predetermined value. The color gamut compression method according to claim 28.
The color gamut compression method, wherein the high saturation region is a region where a color difference ΔE with respect to the first color gamut data is 5 or more. The color gamut compression method according to any one of claims 22 to 29,
A color gamut compression method comprising a step of creating a color gamut conversion lookup table based on an interpolation result obtained by the interpolation step. The color gamut compression method according to any one of claims 23 to 29,
The color gamut compression method, wherein the color signal is a coordinate value in CIELab space.

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