JP2006013608A - Color transformation definition correcting device and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color transformation definition correcting device for correcting a color transformation definition defining the relation of coordinate transformation between a first color space dependent on a first device and a second color space dependent on a second device while making a plurality of coordinate points in the first color space and a plurality of coordinate points in the second color space correspond one to one in which color matching precision is compatible with gray scale reproducibility in high dimension. <P>SOLUTION: With regard to a color determined to deviate from a reproducible gamut by a second device, the degree of deviation from the gamut is determined, and coordinate transformation defined by color a transformation definition is combined with more linear coordinate transformation by an amount corresponding to that degree thus correcting the coordinate points in a second color space corresponding to the coordinate points in a first color space representing that color. Furthermore, a plurality of coordinate points in the second color space subjected to the correction of the color transformation definition are smoothed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates a coordinate conversion relationship between a first color space depending on a first device and a second color space depending on a second device to a plurality of coordinate points in the first color space. Conversion definition correcting device for correcting a color conversion definition defined by associating a plurality of coordinate points of the second color space with one-to-one correspondence, and color conversion that causes a computer to operate as such a color conversion definition correcting device It is related to definition correction program.

  Conventionally, an image (hereinafter referred to as an original image) is obtained by an input device such as a color scanner or an electronic still camera, and image data is obtained. Based on the image data, a printer, a printer, or a display screen is now used. A reproduced image is obtained by reproducing the original image with an output device or the like. In this case, the color conversion definition (input profile) that associates the color on the original image with the color representation in the image data according to the input device, and the color representation in the image data according to the output device such as a printing machine or printer. A color conversion definition (output profile) for associating colors on a reproduced image is obtained, and image data obtained from an original image by an input device is combined with both color conversion definitions (input profile and output profile) 1 Based on one color conversion definition (device link profile), the image data is converted into image data suitable for the output device, and a reproduced image is output based on the image data for the output device. By doing so, it is possible to obtain a reproduced image that is as similar in color as possible to the original document image.

  The same is true between output devices. Next, an example will be described.

  Conventionally, when printing a color image using a printing press, before printing, a color printer or the like is used to create a proof image that is as similar as possible to the color of the image printed by the printing press. It has been made. When creating a proof image with a printer, for example, each of C (Cyan), M (Magenta), Y (Yellow: Yellow), and K (Black: Black) of a printing machine that is about to perform printing. Color conversion definition (print profile) that defines the correspondence between color data representing halftone dots and the color of the actual printed matter that is output based on the color data, and, for example, CMYK of the printer that is outputting the proof image Know the color data representing each halftone percentage and the color conversion definition (printer profile) that defines the correspondence between the color of the proof image that is actually printed out based on the color data. Image data for printing based on one color conversion definition (device link profile) Into image data for printer, to create a proof image based on the image data for the converted printer. By doing so, it is possible to create a proof image that is similar in color to the actual printed matter as much as possible.

  In order to obtain images with matching colors as described above, color conversion definitions (input profiles) for input devices such as color scanners and electronic still cameras, and color conversion definitions for output devices such as printing machines and printers ( Output profile) must be determined accurately.

In determining the color conversion definition such as the input profile and the output profile, for example, in the case of an input device, a color chart in which color patches are arranged is read by the input device and converted into image data, for example, C, M, Y, CMYK color space consisting of four colors of K, or a color space on image data such as an RGB color space consisting of three colors of R (Red: Red), G (Green: Green), and B (Blue: Blue) Such coordinate spaces (referred to as device-dependent color spaces) are determined (CMYK values or RGB values, etc.), and each color patch constituting the same color chart is measured with a spectrocolorimeter. L ^* a ^* b ^* color space or color color space measurement, such as XYZ color space (hereinafter, referred to such a color space and a device-independent color space Obtains colorimetric values (L ^* a ^* b ^* values or XYZ values, etc.) of that), and a plurality of colorimetric values of the plurality of coordinate points of the device-dependent color space and a device-independent color space into a one-to-one The input profile can be obtained by associating.

  In the case of an output device, for example, color patches corresponding to each of a plurality of types of color data in which the network% is sequentially changed to 0%, 10%,..., 100% for each of the four colors of CMYK, for example. The image data corresponding to the color chart is created, the color chart is output by the output device based on the image data, each color patch constituting the output color chart is measured by the spectrocolorimeter, and the color chart The output profile can be obtained by associating the plurality of coordinate points of the device-dependent color space obtained in this way with the plurality of colorimetric values of the device-independent color space in a one-to-one relationship.

  Basically, color conversion definitions such as an input profile and an output profile are obtained in this way, but the number of color patches constituting the color chart is not so large as to correspond to each point of the color conversion definition. Such a correspondence relationship is a correspondence relationship corresponding to sparse coordinate points that are considerably coarse in the color space, and is too rough as a color conversion definition. Therefore, one-to-one correspondence between a plurality of coordinate points in the device-dependent color space and a plurality of colorimetric values in the device-independent color space obtained by measuring the color patches constituting the color chart as described above. The number of one-to-one correspondence pairs between a plurality of coordinate points in the device-dependent color space and a plurality of colorimetric values in the device-independent color space is increased by interpolation or the like based on the association between As a result, a desired color conversion definition is finally obtained.

However, even if the color conversion definition such as the input profile and output profile is accurately obtained as described above, the measurement error by the spectrocolorimeter and the position dependence of the output color in the target device for which the color conversion definition is to be created Add color patches of specific important colors represented by skin color as color patches that make up the color chart in order to improve the color error of color patches due to device characteristics such as sexuality and practical color matching accuracy As a result, the created color conversion definition is distorted, and noise that breaks the monotonicity of changes such as L ^* a ^* b ^* data and XYZ data corresponding to monotonous coordinate changes in the device-dependent color space is included. May end up. If such a noise is included in the created color conversion definition, when an image is output on the device based on the color-converted image data obtained by performing color conversion using this color conversion definition, A color density discontinuous change (hereinafter referred to as a tone jump) occurs in a gradation portion where the color density continuously changes on the color image, and the tone Jumps are visually recognized and can result in degradation of image quality. In addition, when trying to calculate the inverse conversion profile that calculates the coordinate point of the device-dependent color space from the colorimetric values of the device-independent color space based on the created color conversion definition, the noise included in the color conversion definition There is also a possibility that the inverse transformation profile cannot be obtained accurately due to a calculation error factor.

  It is known that the distortion of the color conversion definition is alleviated by performing a smoothing process on the color conversion definition including noise that breaks such monotonicity. If color conversion is performed using the color conversion definition after smoothing processing, tone jump is relaxed and a smooth gradation is expressed, and a color image with high color quality can be output. .

  However, performing the smoothing process on the color conversion definition changes the data of the color conversion definition, which may reduce the accuracy of color matching.

As a color conversion definition correction device that eliminates such problems, the color conversion coordinates after color conversion based on the color conversion definition after the smoothing process is applied to the color conversion definition. Find the color difference between the color represented by the point and the set reference color, and if the calculated color difference is larger than the arbitrarily set reference color difference, the color whose coordinates are corrected so that this color difference is reduced A conversion definition correcting device is disclosed (for example, see Patent Document 1).
JP 2003-331276 A

  The color conversion definition correcting apparatus disclosed in Patent Document 1 performs the smoothing process and the coordinate points of the color space after the color conversion based on the color conversion definition after the smoothing process is performed as described above. In this color conversion definition correcting device, the color conversion accuracy is prevented from being significantly reduced, the predetermined color matching accuracy is maintained, and the density discontinuity is reduced. To achieve both color matching accuracy and gradation reproducibility, but to handle colors that are out of the color range that the output device can reproduce (hereinafter, the color range that the device can reproduce is called gamut) Not mentioned.

  The color conversion definition adjusted to create a high-accuracy color proof is partially distorted. For example, if the target printer gamut is larger than the printer gamut, the color conversion definition When color conversion is performed using the definition, a large gamut is crushed in accordance with the small gamut, and as a result, the gradation tends to be lost at a portion outside the gamut of the printer. Since the lost gradation is difficult to improve even if smoothing processing is performed on the entire color conversion definition, color conversion is performed using the color conversion definition after smoothing processing. Even when the image is output by the device based on the image data after the color conversion, the image quality may be deteriorated. Further, even when the smoothing process is limited as in the correction by the color conversion definition correcting apparatus disclosed in Patent Document 1, for example, a color chart for color matching evaluation in a portion out of the printer gamut When there is a specific important color typified by a skin color for enhancing practical color matching accuracy, color matching accuracy and gradation reproducibility may not be compatible.

  The present invention solves the above-described problems, and a color conversion definition correcting device that achieves both color matching accuracy and gradation reproducibility at a high level, and a color conversion definition correcting program that causes a computer to operate as such a color conversion definition correcting device. Is intended to provide.

The first color conversion definition correcting device of the color conversion definition correcting device according to the present invention that achieves the above-described object comprises:
The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points in the first color space and the first color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated with the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit by the color conversion definition The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree obtained by the above-described deviation degree calculation unit. A conversion definition correction section;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. And a smoothing processing unit for correcting the color conversion definition.

  The first color conversion definition correcting device of the color conversion definition correcting device of the present invention obtains the degree of deviation from the color range for the color determined to be outside the color range that can be reproduced by the second device, Corresponding to the coordinate point of the first color space representing the color by synthesizing the coordinate conversion defined by the color conversion definition and the coordinate conversion that is more linear than the coordinate conversion by the amount corresponding to the degree Since the coordinate point of the second color space is corrected, the color matching accuracy is maintained in the inner portion of the color range, and gradation loss is avoided in the portion outside the color range. Tone reproducibility is maintained. In addition, the first color conversion definition correcting device performs smoothing processing on a plurality of coordinate points of the second color space in the corrected color conversion definition. The distortion of the color conversion definition is alleviated, the tone jump on the output color image is alleviated and a smooth gradation is expressed, and a color image having a high color image quality is obtained. Therefore, according to such a first color conversion definition correcting apparatus, it is possible to achieve both color matching accuracy and gradation reproducibility at a high level.

The second color conversion definition correcting device of the color conversion definition correcting device according to the present invention that achieves the above-described object,
The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points in the first color space and the first color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A reference color setting unit that receives a reference color setting for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the above-described deviation degree calculation unit,
A smoothing processing unit that applies a smoothing process to smooth discontinuities between coordinate points of the second color space in the color conversion definition to correct the color conversion definition. When,
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after the smoothing processing is performed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, after the smoothing processing is performed by the smoothing processing unit A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. .

  The second color conversion definition correcting device of the color conversion definition correcting device of the present invention obtains the degree of deviation from the color range for the color determined to be outside the color range that can be reproduced by the second device, For the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color, the set reference color difference is enlarged by an amount corresponding to the degree. Further, the second color conversion definition correcting device performs a smoothing process on a plurality of coordinate points in the second color space, and a reference color set for the coordinate points in the second color space. When the color difference with the coordinate point of the second color space after the smoothing process is obtained and this color difference is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained Includes correcting the coordinate point of the second color space after the smoothing process to reduce the color difference between the color represented by the coordinate point of the second color space and the reference color. is there. Therefore, according to such a second color conversion definition correcting device, the color matching accuracy is prevented from being significantly reduced in the inner portion of the color range, the predetermined color matching accuracy is maintained, and the color range is maintained. In a portion that is out of the range, gradation deletion is avoided and gradation reproducibility is maintained.

Furthermore, the third color conversion definition correcting device of the color conversion definition correcting device of the present invention that achieves the above-described object is
The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points in the first color space and the first color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated with the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit by the color conversion definition The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree obtained by the above-described deviation degree calculation unit. A conversion definition correction section;
A reference color setting unit that receives a reference color setting for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the above-described deviation degree calculation unit,
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A smoothing processing unit for correcting the color conversion definition;
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after the smoothing processing is performed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, after the smoothing processing is performed by the smoothing processing unit A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. .

  The third color conversion definition correcting device of the color conversion definition correcting device of the present invention obtains the degree of deviation from the color range for the color determined to be outside the color range that can be reproduced by the second device, Corresponding to the coordinate point of the first color space representing the color by synthesizing the coordinate conversion defined by the color conversion definition and the coordinate conversion that is more linear than the coordinate conversion by the amount corresponding to the degree The coordinate point of the second color space to be corrected is corrected. In addition, the third color conversion definition correcting device can coordinate the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range reproducible by the second device. As for the point, the set reference color difference is enlarged by an amount corresponding to the above degree. Further, the third color conversion definition correcting device performs a smoothing process on a plurality of coordinate points in the second color space in the color conversion definition after correction, and coordinates points in the second color space. The color difference between the reference color set for and the coordinate point of the second color space after the smoothing process is obtained, and this color difference is the second color space when the color difference is obtained. If the difference is larger than the reference color difference with respect to the coordinate point, the coordinate point of the second color space after the smoothing process is corrected and the color represented by the coordinate point of the second color space and the reference color It is intended to reduce the color difference. Therefore, according to the third color conversion definition correcting apparatus, the color matching accuracy can be prevented from being greatly reduced in the inner portion of the color range, the predetermined color matching accuracy can be maintained, and the color range can be maintained. In a portion that is out of the range, tone deletion is avoided and tone reproducibility is maintained. That is, according to such a third color conversion definition correcting apparatus, it is possible to achieve both color matching accuracy and gradation reproducibility at a high level.

The first color conversion definition correction program of the color conversion definition correction program of the present invention that achieves the above object is
Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on the first device and a second color space dependent on the second device; A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in a second color space in a one-to-one correspondence. There,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated with the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit by the color conversion definition The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree obtained by the above-described deviation degree calculation unit. A conversion definition correction section;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. And a smoothing processing unit for correcting the color conversion definition.

  The first color conversion definition correction program of the color conversion definition correction program of the present invention is installed when the first color conversion definition correction program is installed and operated on the computer. It is configured to operate as a first color conversion definition correcting device among the definition correcting devices.

The second color conversion definition correction program of the color conversion definition correction program of the present invention that achieves the above object is
Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on the first device and a second color space dependent on the second device; A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in a second color space in a one-to-one correspondence. There,
A reference color setting unit that receives a reference color setting for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the above-described deviation degree calculation unit,
A smoothing processing unit that applies a smoothing process to smooth discontinuities between coordinate points of the second color space in the color conversion definition to correct the color conversion definition. When,
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after the smoothing processing is performed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, after the smoothing processing is performed by the smoothing processing unit And a coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small.

  The second color conversion definition correction program of the color conversion definition correction program of the present invention is installed when the second color conversion definition correction program is installed in a computer and operated. It is configured to operate as a second color conversion definition correcting device among the definition correcting devices.

Furthermore, the third color conversion definition correction program of the color conversion definition correction program of the present invention that achieves the above-described object is
Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on the first device and a second color space dependent on the second device; A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in a second color space in a one-to-one correspondence. There,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated with the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit by the color conversion definition The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree obtained by the above-described deviation degree calculation unit. A conversion definition correction section;
A reference color setting unit that receives a reference color setting for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the above-described deviation degree calculation unit,
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A smoothing processing unit for correcting the color conversion definition;
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after the smoothing processing is performed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, after the smoothing processing is performed by the smoothing processing unit And a coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small.

  The third color conversion definition correction program among the color conversion definition correction programs of the present invention is such that when the third color conversion definition correction program is installed and operated in a computer, the computer converts the color conversion definition correction program of the present invention. It is configured to operate as a third color conversion definition correcting device among the definition correcting devices.

  In addition, the constituent elements such as the determination unit constituting the color conversion definition correction program of the present invention may be one in which the function of one constituent element is carried by one program component, and a plurality of functions of one constituent element. May be carried by the program parts, and the functions of a plurality of components may be carried by one program part. In addition, these components may execute such actions themselves, or may be executed by giving instructions to other programs and program components incorporated in the computer. Also good.

  In the color conversion definition correcting device and the color conversion definition correcting program of the present invention, the same names are given to the components, but these components mean hardware and software in the color conversion definition correcting device, In the color conversion definition correction program, it means only software.

  According to the present invention, there are provided a color conversion definition correcting apparatus that achieves both color matching accuracy and gradation reproducibility at a high level, and a color conversion definition correcting program that causes a computer to operate as such a color conversion definition correcting apparatus. .

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

  In the present embodiment, the color on the proof image printed out by the color printer matches or sufficiently approximates the color on the printed matter obtained by the printing press corresponding to an example of the first device according to the present invention. An example of correcting a device link profile corresponding to an example of color conversion definition according to the present invention will be described.

  FIG. 1 is an overall configuration diagram of a printing and proof image creation system employing a device link profile modified according to an embodiment of the present invention. Here, first, the positioning of the present invention will be described with reference to FIG.

  In the color scanner 10, the document image 11 is read, and from C (Cyan), M (Magenta), Y (Yellow: yellow), and K (Black: black) representing the read document image 11. The four color separation image data is generated. The CMYK image data is input to the workstation 20. In the workstation 20, an electronic plate collection based on the input image data is performed by the operator, and image data representing an image for printing is generated. The image data for printing is input to the film printer 30 when printing is performed, and the film printer 30 creates CMYK printing film originals corresponding to the input image data.

  A printing plate is created from the printing film original plate, and the created printing plate is mounted on the printing machine 40. Ink is applied to the printing plate mounted on the printing machine 40, and the applied ink is transferred onto a printing sheet to form a printed image 41 on the sheet.

  A series of operations in which a film original plate is prepared by the film printer 30, a printing plate is further prepared and mounted on the printing machine 40, ink is applied to the printing plate, and printing is performed on paper is a large-scale operation. Cost too. For this reason, before the actual printing operation is performed, a proof image 61 is created as follows by the printer 60 corresponding to an example of the second device according to the present invention, and the finished prediction of the printed image 41 is predicted in advance. Done.

  In creating a proof image, image data created by electronic plate collection on the workstation 20 is input to the personal computer 50. Here, the image data input to the personal computer 50 is description language data described in so-called PDL (Page Description Language). In the personal computer 50, the image data is developed into a bitmap by a so-called RIP (Raster Image Processor). The converted CMYK four-color image data. The CMYK four-color image data is substantially the same as the image data for printing input to the film printer 30.

  The spectrocolorimeter 70 and the personal computer 80 shown in FIG. 1 are related to the creation and correction of profiles, and the personal computer 80 constitutes an embodiment of the color conversion definition correcting apparatus according to the present invention. The spectrocolorimeter 70 is an auxiliary device. The personal computer 50 stores a device link profile having a LUT (Look Up Table) format created and modified in advance using the personal computer 80. The CMYK four-color printing image data described above is converted into CMYK four-color image data suitable for the printer 60 by referring to the device link profile in the personal computer 50. The printer 60 receives CMYK four-color image data for the printer, and the printer 60 creates a proof image 61 based on the input CMYK four-color image data for the printer.

  Here, the degree of color matching between the image 41 obtained by printing by the printer 40 and the proof image obtained by the printer 60 is determined by the device link profile in the personal computer 50. This device link profile is created for each print condition for each printer.

  Further, FIG. 1 shows only one printing machine, but there may be a plurality of printing machines, or even a single printing machine may have a plurality of different printing conditions. Often, the device link profile is created in accordance with each of a plurality of printing conditions including differences in printing presses. That is, the device link profile is created in accordance with a combination of each printing condition and each printer (each printing condition when a plurality of printing conditions exist in one printer). A method for creating the device link profile will be described later.

  Thus, by creating a proof image and confirming the proof image, it is possible to predict the print finish in advance.

  Here, the feature of the printing and proof image creation system shown in FIG. 1 as an embodiment of the present invention relates to the processing contents executed in the personal computer 80. First, the personal computer will be described below. 80 will be described.

  2 is an external perspective view of the spectrocolorimeter 70 shown as a block in FIG. 1 and a personal computer 80 constituting one embodiment of the color conversion definition correcting apparatus of the present invention. FIG. 3 is a hardware diagram of the personal computer 80. It is a hardware block diagram.

  Here, an embodiment of the color conversion definition correcting apparatus of the present invention is realized by the hardware and OS (Operation System) of the personal computer 80 and the color conversion definition correcting program installed and executed in the personal computer 80. It is configured.

A spectrocolorimeter 70 shown in FIG. 2 is mounted with a color chart 90 in which a plurality of color patches are arranged, and the color of each of the plurality of color patches constituting the color chart 90 is measured. A colorimetric value representing the color of each color patch obtained by the colorimetry by the spectrocolorimeter 70 (here, L ^* a ^* b ^* value as an example of the colorimetric value) passes through the cable 91. And input to the personal computer 80.

  The color chart 90 is created by printing on the printing machine 40 shown as one block in FIG. 1 or by printing output on the printer 60. The personal computer 80 is configured by each of the color charts 90 constituting the color chart 90. The color data corresponding to the color patch (coordinate points in the device-dependent color space; each value of CMYK or RGB) is known. In this personal computer 80, the color data of each color patch of the color chart 90 and the spectrocolorimeter Based on the colorimetric values obtained in 70, a print profile and a printer profile are created. A detailed description of this point will be given later. Here, the hardware configuration of the personal computer 80 will be described next.

  As shown in FIG. 2, the personal computer 80 includes a main body device 81, an image display device 82 that displays an image on a display screen 82 a according to an instruction from the main body device 81, and the main body device 81. By specifying an arbitrary position on the display screen 82a and a keyboard 83 for inputting various information according to key operations, an instruction corresponding to, for example, an icon or the like displayed at that position at the time of the specification is input. A mouse 84 is provided. The main unit 81 has an FD loading port 81a for loading a flexible disk (FD) and a CD-ROM loading port 81b for loading a CD-ROM.

  As shown in FIG. 3, the main body 81 includes a CPU 811 that executes various programs, a main memory 812 that reads programs stored in the hard disk device 813 and develops them for execution by the CPU 811, and various programs. , A hard disk device 813 storing data and the like, an FD drive 814 loaded with the FD 100 and accessing the loaded FD 100, a CD-ROM 110 loaded with the CD-ROM 110, and a CD-ROM drive 815 accessing the loaded CD-ROM 110 An I / O interface 816 that is connected to the spectrocolorimeter 70 shown in FIGS. 1 and 2 and receives colorimetric values from the spectrophotometer 70 is built-in. The image display device 82, the keyboard 83, and the mouse 84 are connected to each other via the bus 85. It is.

  Here, the CD-ROM 110 stores a color conversion definition correction program for operating the personal computer 80 as a color conversion definition correction device. The CD-ROM 110 is loaded into a CD-ROM drive 815, and The color conversion definition correction program stored in the CD-ROM 110 is uploaded to the personal computer 80 and stored in the hard disk device 813.

  Note that the profile creation function described below by the personal computer 80 is not the subject of the present invention, and it is assumed that a program or the like necessary for realizing the function has already been installed in the personal computer 80. .

  Next, a profile creation function built in the personal computer 80 will be described.

  In general, the printer profile described below is already created by the printer manufacturer and delivered together with the printer. Therefore, it is not necessary to create a new printer profile here. A basic creation method when it is newly created will be described.

  FIG. 4 is an explanatory diagram of profile creation and correction.

  The correction of the profile here is a correction for improving the accuracy of color matching in the color conversion based on the created profile, and is different from the “correction of color conversion definition” in the present invention.

  Here, a method for creating a print profile will be described first.

For example, the workstation 20 shown in FIG. 1 generates halftone data represented by four colors of CMYK that are sequentially changed, for example, 0%, 10%,..., 100%, and is generated as described above according to the printing procedure described above. A color chart 42 is created based on the halftone data. Each color patch constituting the color chart 42 is measured with a spectrocolorimeter 70 (see FIG. 2). By doing so, obtain the CMYK values of the CMYK color space of CMYK four colors, the correspondence between the L ^* a ^* b ^* values of the L ^* a ^* b ^* color space.

Since the correspondence obtained in this way is limited in the number of color patches constituting the color chart, the CMYK values and the L ^* a ^* b ^* values for coordinate points with a fairly coarse interval in the CMYK color space are used. It is correspondence. For this reason, after obtaining this correspondence, an interpolation operation or the like is applied to this correspondence to create a print profile 400 in which the correspondence regarding coordinate points at desired fine intervals in the CMYK space is defined.

  FIG. 5 is a conceptual diagram of the print profile 400.

The print profile 400 receives halftone data represented by CMYK, and the halftone data represented by CMYK is converted into a colorimetric value represented by L ^* a ^* b ^* . Here, the print profile 400 for converting the halftone data represented by CMYK into a colorimetric value represented by L ^* a ^* b ^* is represented by T.

  Next, returning to FIG. 4, a printer profile creation method will be described.

This printer profile creation method is the same as the print profile 400 creation method except that the output device that outputs the color chart is not a printing press but a printer. That is, here, in the personal computer 50 shown in FIG. 1, the halftone data represented by four colors of CMYK is sequentially changed to 0%, 10%,... The data is sent to the printer 60, and the printer 60 prints out a color chart 62 based on the halftone data. Here, it is assumed that a color chart 62 of the same type as the color chart 42 created by printing on the printing press 40 is created to create the print profile 400, and each color patch constituting the color chart 62 is spectrally measured. The color is measured with a total of 70 (see FIG. 2). Thereby, obtained about the printer 60, the CMYK values of the CMYK color space of four colors of CMYK, the correspondence between the L ^* a ^* b ^* values of the L ^* a ^* b ^* color space.

Since the correspondence obtained in this way is limited in the number of color patches constituting the color chart, as in the case of creating the print profile 400, the CMYK values for coordinate points with fairly coarse intervals in the CMYK color space. And a L ^* a ^* b ^* value, and an interpolation operation is applied to this correspondence relationship to define a printer profile 500 in which a correspondence relationship regarding coordinate points at desired fine intervals in the CMYK space is defined. Created.

  FIG. 6 is a conceptual diagram of the printer profile 500.

This printer profile 500 receives halftone data represented by CMYK, and the halftone data represented by CMYK is converted into a colorimetric value represented by L ^* a ^* b ^* . Here, a printer profile 500 (forward conversion printer profile) for converting the halftone data represented by CMYK into a colorimetric value represented by L ^* a ^* b ^* is represented by P, and its inverse conversion, that is, L A printer profile (reverse conversion printer profile) for converting the colorimetric value represented by ^* a ^* b ^* into halftone data represented by CMYK is represented by P- ¹ .

  Here, the printer 60 is described as a printer that outputs an image based on halftone data represented by CMYK. However, for example, a printer that outputs an image based on RGB data is also used by the personal computer 50. By generating data defined in RGB space and outputting a color chart, a printer profile suitable for the printer can be created in the same manner.

  However, here, it is assumed that the printer 60 that outputs an image based on halftone data represented by CMYK is used.

  FIG. 7 is a conceptual diagram of a device link profile 600 in which the print profile 400 shown in FIG. 5 and the printer profile 500 shown in FIG. 6 are combined.

This device link profile 600 is a combination of a print profile 400 (T) and an inverse conversion printer profile (P ⁻¹ ), and the halftone data represented by CMYK for printing is used as the print profile 400 (T). Table with CMYK for the printer by L ^* a ^* b ^* is converted into colorimetric values represented by, and then the L ^* a ^* b ^* in the inverse transform printer profile colorimetric values represented (P ^-1) by The result equivalent to the two-stage conversion of conversion to halftone data is realized by one data conversion. That is, this device link profile 600 converts image data defined in the CMYK color space for printing into image data defined in the CMYK color space for printers. Based on the halftone data represented by CMYK for a printer generated by the device link profile 600, the printer 60 can output a proof image that is as similar as possible to the color of the image to be printed.

  Such a device link profile 600 is created by the personal computer 80 constituting the printing and proof image creation system shown in FIG. 1, and the created device link profile 600 is used as the personal computer constituting the printing and proof image creation system shown in FIG. After being installed in the computer 50 and converting image data described in PDL input from the workstation 20 into CMYK image data, the CMYK image data for printing is converted into a printer using the device link profile 600. 1 is converted to CMYK image data for the printer, and an image based on the CMYK image data for the printer is printed out by the printer 60, so that it is the same color as the image printed by the printer 40 shown in FIG. Pull resembling Full image is created.

  Next, referring back to FIG. 4, a conventional correction method for the device link profile 600 for improving the accuracy of color matching in color conversion based on the device link profile 600 will be described.

  For example, a network represented by CMYK four colors for printing represented by a color chart in which color patches including specific important colors represented by skin color are arranged (hereinafter, this color chart is referred to as a color chart for color matching evaluation). The color chart 43 based on the% data is created according to the printing procedure described above. Each color patch constituting the color chart 43 is measured by the spectrocolorimeter 70 (see FIG. 2).

  Further, the device link profile 600 created as described above is installed in the personal computer 50 constituting the printing and proof image creation system shown in FIG. 1, and the printing is represented by the color matching evaluation color chart described above. The network% data expressed in four colors of CMYK is converted into CMYK image data for a printer using the device link profile 600, and the printer 60 prints a color chart 64 based on the CMYK image data for the printer. Output. Each color patch constituting the color chart 64 is measured by the spectrocolorimeter 70 (see FIG. 2).

  The device link profile 600 is based on the color difference between the colorimetric value obtained by measuring each color patch constituting the color chart 43 and the colorimetric value obtained by measuring each color patch constituting the color chart 64. By correcting the above, it is possible to obtain a device link profile with more practical color matching accuracy.

However, as described in the “Background Art” section, the color caused by the characteristics of the device such as the measurement error by the spectrocolorimeter 70 and the position dependency of the output color in the target device for which the profile is to be created. Specificity represented by skin color in order to increase practical color matching accuracy such as correction of device link profile 600 for improving color matching accuracy in color conversion based on the above-described device link profile 600 and color error of the patch When the color patches of the important colors are added as the color patches constituting the color chart, the created profile may be distorted, and noise that disrupts the monotonicity of data changes may be included. If such a noise is included in the created profile, when an image is output on the device based on the color-converted image data obtained by performing color conversion using this profile, In the gradation portion where the color density changes continuously, a discontinuous change in the color density (hereinafter referred to as a tone jump) occurs, and the tone jump is visually May be recognized and may result in degradation of image quality. In addition, attempts to find by calculation the inverse conversion profile to determine the CMYK values of the L ^* a ^* b ^* color space L ^* a ^* b ^* consists four CMYK from the value CMYK color space based on the created profile In some cases, noise included in the profile may cause a calculation error, and the inverse transformation profile may not be accurately obtained.

  It is known that the above-described smoothing process is performed on a profile including noise that breaks such monotonicity, so that distortion of the profile is alleviated. If color conversion is performed using a profile, tone jump is relaxed and a smooth gradation is expressed, and a color image with high color quality can be output. However, since smoothing the profile changes the profile data, the smoothness of the device link profile 600 is corrected in order to improve the color matching accuracy as described above. There is a possibility that the accuracy of color matching is lowered by the conversion processing.

  As described in the “Background Art” and “Problems to be Solved by the Invention” section, such a problem is caused by performing a smoothing process on the profile and a profile after the smoothing process is performed. Obtain the color difference between the color represented by the coordinate point of the color space after color conversion based on the color and the set reference color, and if the calculated color difference is larger than the arbitrarily set reference color difference, this color difference is small. For example, a color range that can be reproduced by a target printing machine (hereinafter, a color range that can be reproduced by various devices is referred to as a gamut) is a gamut of a printer. If the color conversion is performed using the color conversion definition, the large gamut collapses to fit the small gamut, and as a result, is out of the printer gamut. Portions tend to gradation is lost in.

  Since the lost gradation is difficult to improve even if the entire profile is smoothed, even if color conversion is performed using the profile after smoothing, When an image is output by the device based on the image data after the color conversion, there is a possibility that the image quality is deteriorated. Further, even when smoothing processing is limited as described above, for example, a flesh color for enhancing practical color matching accuracy included in the color chart for color matching evaluation in a portion out of the printer gamut When there is a specific important color represented by the above, there is a possibility that color matching accuracy and gradation reproducibility may not be compatible.

  FIG. 8 is a diagram in which Y and M values after the halftone data represented by CMYK are color-converted with the profile after the smoothing process are plotted. The horizontal axis represents the dot percentage of M (Magenta) ink (gradation in which the color continuously changes from C color to B (Blue) color) with respect to the dot percentage of C (Cyan) ink being 100%. The vertical axis indicates the dot percentage of Y (Yellow: yellow) ink with respect to 100% dot percentage of C ink (gradation in which the color continuously changes from C color to R (Red) color).

  FIG. 8 shows an example in which the values of Y and M after color conversion by the device link profile modified so that the above-described smoothing process is restricted are plotted. The example shown in FIG. In this case, gradation loss appears remarkably in a portion where the Y ink halftone is 5% or less and a portion where the Y ink halftone is 75% or more.

  Therefore, next, the color matching accuracy and gradation reproducibility realized by the personal computer 80 shown in FIGS. 1, 2, and 3 operating as an embodiment of the color conversion definition correcting apparatus of the present invention are obtained. An example of a color conversion definition correcting device compatible with high dimensions will be described.

  FIG. 9 is a diagram showing an embodiment of the color conversion definition correction program of the present invention.

  The color conversion definition correction program 210 shown in FIG. 9 is stored in the CD-ROM 110 shown in FIG.

  The color conversion definition correction program 210 is executed in the personal computer 80 shown in FIGS. 1, 2, and 3, and the personal computer 80 is used for printing corresponding to an example of the first color space referred to in the present invention. Color conversion definition correction for correcting a device link profile for converting image data defined in the CMYK color space into image data defined in the CMYK color space for a printer corresponding to an example of the second color space according to the present invention A color conversion definition correction program that operates as a device. The color conversion definition correction program 210 includes a determination unit 211, a deviation degree calculation unit 212, a color conversion definition correction unit 213, a reference color setting unit 214, a reference color difference setting unit 215, a reference color difference enlargement unit 216, A smoothing processing unit 217, a color difference calculation unit 218, and a coordinate point correction unit 219 are included.

  The operation of each element of the color conversion definition correction program 210 will be described later.

  FIG. 10 is a functional block diagram showing an embodiment of the color conversion definition correcting apparatus of the present invention.

  The color conversion definition correcting apparatus 300 shown in FIG. 10 is loaded with the color conversion definition correcting program 210 shown in FIG. 9 on the personal computer 80 shown in FIGS. This is realized by being executed in the personal computer 80.

  The color conversion definition correcting apparatus 300 shown in FIG. 10 corrects a device link profile for converting image data defined in the CMYK color space for printing into image data defined in the CMYK color space for printers. The color conversion definition correcting device 300 includes a determination unit 311, a degree of deviation calculation unit 312, a color conversion definition correction unit 313, a reference color setting unit 314, a reference color difference setting unit 315, and a reference color difference enlargement unit. 316, a smoothing processing unit 317, a color difference calculation unit 318, and a coordinate point correction unit 319 are provided.

  The color conversion definition correcting apparatus 300 includes a determination unit 311, a degree of deviation calculation unit 312, a color conversion definition correction unit 313, a reference color setting unit 314, a reference color difference setting unit 315, a reference color difference enlargement unit 316, and a smoothing process. Each of the elements of the unit 317, the color difference calculation unit 318, and the coordinate point correction unit 319 includes a determination unit 211, a deviation degree calculation unit 212, and a color conversion as software components constituting the color conversion definition correction program 210 shown in FIG. Each element of the definition correction unit 213, the reference color setting unit 214, the reference color difference setting unit 215, the reference color difference enlargement unit 216, the smoothing processing unit 217, the color difference calculation unit 218, and the coordinate point correction unit 219, and software components thereof The hardware and OS (Operat) of the personal computer 80 shown in FIGS. It is composed of a combination of on System) and application programs.

  Hereinafter, by describing each element of the color conversion definition correcting apparatus 300 shown in FIG. 10, each element of the color conversion definition correcting program 210 shown in FIG. 9 will also be described.

  Here, the conceptual operation of each element of the color conversion definition correcting apparatus 300 will be described, and the specific operation of each element will be described later.

  The determination unit 311 of the color conversion definition correction apparatus 300 shown in FIG. 10 is an element corresponding to the determination unit 211 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and CMYK for printing in the device link profile. For the color represented by the CMYK value in the color space, the inside and outside of the printer gamut is determined. The determination unit 311 shows an example of the function of the determination unit referred to in the present invention, and the function is a program component built in the main unit 81 of the personal computer 80 shown in FIGS. This is mainly realized by the CPU 811 that executes the determination unit 211 (see FIG. 9).

  In each element of the color conversion definition correcting apparatus 300 described below, the function of each element is mainly realized by the CPU 811 incorporated in the main body 81 of the personal computer 80 shown in FIGS. Therefore, in order to avoid redundant description, description of these elements on hardware is omitted.

  The detachment degree calculation unit 312 is an element corresponding to the detachment degree calculation unit 212 of the color conversion definition correction program 210 shown in FIG. 9 in the application software, and is determined to be out of the printer gamut by the determination unit 311. The degree to which the color deviates from the printer's gamut is obtained. The detachment degree calculation unit 312 shows an example of the function of the detachment degree calculation unit according to the present invention.

  Further, the color conversion definition correction unit 313 is an element corresponding to the color conversion definition correction unit 213 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and is determined to be out of the printer gamut by the determination unit 311. By changing the CMYK value of the CMYK color space for the printer that is associated with the CMYK value of the CMYK color space for printing representing the generated color by the device link profile, thereby defining the coordinate transformation defined by the device link profile In addition, the device link profile is corrected by synthesizing the coordinate transformation that is more linear than the coordinate transformation in accordance with the degree obtained by the deviation degree calculation unit 312. The color conversion definition correcting unit 313 shows an example of the function of the color conversion definition correcting unit referred to in the present invention.

  The reference color setting unit 314 is an element corresponding to the reference color setting unit 214 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and the CMYK value of the CMYK color space for the printer in the device link profile. The reference color is set for. The reference color setting unit 314 shows an example of the function of the reference color setting unit referred to in the present invention.

  The reference color difference setting unit 315 is an element corresponding to the reference color difference setting unit 215 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and receives an arbitrary reference color difference setting. The reference color difference setting unit 315 shows an example of the function of the reference color difference setting unit referred to in the present invention.

  The reference color difference enlargement unit 316 is an element corresponding to the reference color difference enlargement unit 216 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and is determined to be out of the printer gamut by the determination unit 311. The degree obtained by the deviation degree calculation unit 312 for the reference color difference set by the reference color difference setting unit 315 for the CMYK value of the CMYK color space for the printer corresponding to the CMYK value of the CMYK color space for printing representing colors. It is expanded by the amount corresponding to The reference color difference enlargement unit 316 shows an example of the function of the reference color difference enlargement unit according to the present invention.

  The smoothing processing unit 317 is an element corresponding to the smoothing processing unit 217 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and is a device after being corrected by the color conversion definition correction unit 313. The device link profile is corrected by performing a smoothing process for smoothing discontinuity between the CMYK values of the CMYK color space for the printer in the link profile. The smoothing processing unit 317 shows an example of the function of the smoothing processing unit referred to in the present invention.

  Further, the color difference calculation unit 318 is an element corresponding to the color difference calculation unit 218 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and the reference color and smoothing process set by the reference color setting unit 314 A color difference from the color represented by the CMYK value in the CMYK color space for the printer after the smoothing process is performed by the unit 317 is obtained. The color difference calculation unit 318 shows an example of the function of the color difference calculation unit referred to in the present invention.

  Further, the coordinate point correction unit 319 is an element corresponding to the coordinate point correction unit 219 of the color conversion definition correction program 210 shown in FIG. 9 on the application software, and the color difference obtained by the color difference calculation unit 318 is the color difference. When the difference is larger than the reference color difference with respect to the CMYK value of the CMYK color space for the printer when obtained, the CMYK value of the CMYK color space for the printer after the smoothing processing by the smoothing processing unit 317 is performed. The correction is made so that the color difference between the color represented by the CMYK value of the CMYK color space for the printer and the reference color becomes small. A specific correction method will be described later. The coordinate point correction unit 319 shows an example of the function of the coordinate point correction unit referred to in the present invention.

  Hereinafter, embodiments of the present invention will be described more specifically. In the following description, detailed description overlapping with the description of the function of creating the print profile, printer profile, and device link profile by the personal computer 80 described above will be omitted.

  FIG. 11 is a flowchart showing an embodiment of a processing flow in the color conversion definition correcting apparatus of the present invention.

  Here, an example in which the above-described device link profile 600 (see FIG. 4) is specifically modified will be described.

  Here, a process of determining inside / outside of the printer gamut (step 1), a process of calculating the color difference ΔE1 deviating from the printer gamut (step S2), and a process of correcting the device link profile (step S3) A process of setting a reference color (step S4), a process of setting a reference color difference A (step S5), a process of expanding the reference color difference A (step S6), a process of smoothing processing (step S7), A process of calculating the color difference ΔE2 (step S8), a process of comparing the color difference ΔE2 with the reference color difference A (step S9), and a process of correcting the CMYK value of the CMYK color space for the printer (step S10) are shown. These processes are processed by the personal computer 80 shown in FIGS.

First, in the process of determining the inside / outside of the printer gamut (step 1), the determination unit 311 (see FIG. 10) determines the colors represented by the CMYK values in the CMYK color space for printing in the device link profile 600 (see FIG. 4). The inside / outside of the gamut of the printer 60 (see FIG. 1) is determined. Here, first, the CMYK values for printing are converted into L ^* a ^* b ^* values in the printing profile 400 (see FIGS. 4 and 5) used for creating the device link profile 600 (see FIG. 4). Is done. Next, in the device link profile 600 (see FIG. 4), the CMYK values for printing are converted into CMYK values for the printer, and the printer profile used when the device link profile 600 (see FIG. 4) is created. At 500 (see FIGS. 4 and 6), the CMYK values for this printer are converted to L ^* a ^* b ^* values. The color difference between the pair of L ^* a ^* b ^* values corresponding to the CMYK values for printing before conversion obtained in this way is obtained. In the present embodiment, when the color difference is within 1, it is determined that it is within the gamut of the printer 60 (see FIG. 1), and when this color difference is 1 or more, it is determined that it is outside the gamut of the printer 60 (see FIG. 1). The A print profile 400 (see FIGS. 4 and 5) and a printer profile 500 (see FIGS. 4 and 6) used to create the device link profile 600 (see FIG. 4) are an ICC (International Color Consortium): In the case of an ICC format profile that conforms to the OS (Operation System) environment-independent profile standard proposed by the International Color Consortium), the printer uses the gamut tag to determine the color represented by the CMYK value for printing. The inside / outside of 60 (see FIG. 1) gamuts may be determined.

Next, in the process of calculating the color difference ΔE1 deviating from the gamut of the printer 60 (see FIG. 1) (step S2), the color determined to be out of the gamut of the printer 60 (see FIG. 1) in step 1 is deviated. A color difference ΔE1 deviating from the gamut of the printer 60 (see FIG. 1) is obtained by the degree calculation unit 312 (see FIG. 10). Note that, as described above, the detachment degree calculation unit 312 (see FIG. 10) determines the degree of detachment from the printer gamut for the color determined by the determination unit 311 (see FIG. 10) to be out of the printer gamut. Here, an example of obtaining a color difference as an example of the degree will be described. Here, first, a plurality of CMYK values for printers corresponding to the L ^* a ^* b ^* values obtained by the conversion by the printer profile 500 (see FIGS. 4 and 6) in Step 1 are slightly changed. A plurality of L ^* a ^* b ^* values obtained by converting each of the CMYK values by the printer profile 500 (see FIGS. 4 and 6) are obtained, and printing is performed among the plurality of L ^* a ^* b ^* values. profile 400 (see FIGS. 4 and 5) as the color difference is smallest between the L ^* a ^* b ^* values obtained by being converted in the on gamut boundary of the printer 60 (see FIG. 1) L ^* a ^* b ^* value is determined. Next, the L ^* a ^* b ^* value corresponding to the CMYK value for printing representing the color determined to be out of the gamut of the printer 60 (see FIG. 1) in step 1, and on the gamut boundary as described above. The color difference from the determined L ^* a ^* b ^* value is obtained. This color difference corresponds to the distance between the gamut of the printer 60 (see FIG. 1) and the color deviated from the gamut, and represents the degree of deviating from the gamut.

  Next, in the process of correcting the device link profile (step S3), the color determined by the color conversion definition correcting unit 313 (see FIG. 10) to be outside the gamut of the printer 60 (see FIG. 1) in step 1 is displayed. The CMYK values for the printer that are associated with the printed CMYK values by the device link profile 600 (see FIG. 4) are corrected. Specifically, for the coordinate transformation defined by the device link profile 600 (see FIG. 4), the coordinate transformation giving priority to the gradation over the coordinate transformation of the printer 60 (see FIG. 1) obtained in step 2 is performed. The device link profile 600 (see FIG. 4) is corrected so as to be synthesized by an amount corresponding to the color difference ΔE1 that is out of gamut.

  Here, the synthesis in step 3 will be described with reference to FIG. 12, and the effect of step 3 will be described with reference to FIG.

  FIG. 12 is a diagram illustrating an example of weights that are employed according to the color difference ΔE1 in the synthesis in Step 3. The horizontal axis indicates the color difference ΔE1 that is out of the gamut of the printer 60 (see FIG. 1), and the vertical axis indicates the weight.

  In FIG. 12, the weight for the coordinate transformation defined by the device link profile 600 (see FIG. 4), which is adopted according to the color difference ΔE1 deviated from the gamut of the printer 60 (see FIG. 1) obtained in step 2, In addition, a weight for coordinate transformation giving priority to gradation over this coordinate transformation is shown.

  A solid line in FIG. 12 represents a weighting factor W0 for coordinate transformation defined by the device link profile 600 (see FIG. 4), and this weighting factor W0 is obtained by the following equation (1). .

W0 = 1−1 / ΔE1 (1)
However,
ΔE1> 1
Also, what is indicated by a broken line in FIG. 12 represents a weighting factor W1 for coordinate transformation that prioritizes gradation over coordinate transformation defined by the device link profile 600 (see FIG. 4). W1 is obtained by the following equation (2).

W1 = 1-W0 (2)
The coordinates obtained by using the weighting factors W0 and W1 corresponding to the color difference ΔE1 thus obtained and coordinate conversion defined by the device link profile 600 (see FIG. 4) giving priority to gradation over the coordinate conversion. The device link profile 600 (see FIG. 4) is modified by synthesizing the conversion.

  FIG. 13 is a diagram in which Y and M values are plotted after halftone data represented by CMYK is color-converted with the device link profile subjected to the above correction. The horizontal axis represents the dot percentage of M (Magenta) ink (gradation in which the color continuously changes from C color to B (Blue) color) with respect to the dot percentage of C (Cyan) ink being 100%. The vertical axis indicates the dot percentage of Y (Yellow: yellow) ink with respect to 100% dot percentage of C ink (gradation in which the color continuously changes from C color to R (Red) color).

  FIG. 13 shows Y and Y after color conversion by the device link profile after the correction in step S3 is applied to the device link profile that has been corrected to limit the smoothing process shown in FIG. An example in which the value of M is plotted is shown. As described above, in the example shown in FIG. 8, gradation loss is noticeably observed in the portion where the Y ink halftone is 5% or less and in the portion where the Y ink halftone is 75% or more. In the example shown in FIG. 13, it can be confirmed that the gradation reproducibility is maintained by avoiding the deletion of the gradation in those portions.

  Next, returning to FIG. 11, the description of the flowchart in which the device link profile 600 (see FIG. 4) is specifically modified will be continued.

Next, in the process of setting the reference color (step S4), the reference color is set by the reference color setting unit 314 (see FIG. 10) for the CMYK values for the printer in the device link profile 600 (see FIG. 4). Is done. Here, first, a desired color is represented from a color chart 43 (see FIG. 4) in which color patches including specific important colors typified by skin color are arranged to improve practical color matching accuracy. The operator selects a CMYK value. Next, upon selection of CMYK values by the operator, the selected CMYK values are converted into CMYK values for the printer by the device link profile 600 (see FIG. 4), and the device link profile 600 (see FIG. 4) is further converted. In the printer profile 500 (see FIGS. 4 and 6) used for creation, the CMYK values for this printer are converted into L ^* a ^* b ^* values. The L ^* a ^* b ^* value obtained in this way is set as the reference color. Hereinafter, description will be continued assuming that the set L ^* a ^* b ^* values are representatively represented as (L0, a0, b0).

  Next, in the process of setting the reference color difference A (step S5), an input operation is received from the keyboard 83 (see FIGS. 2 and 3) and the mouse 84 (see FIGS. 2 and 3) provided in the personal computer 80. Thus, an arbitrary reference color difference A is set by the reference color difference setting unit 315 (see FIG. 10). Here, from experience, a color difference that prevents a tone jump from being visually recognized in the output color image is set as the reference color difference.

  Next, in the process of enlarging the reference color difference A (step S6), the CMYK for printer corresponding to the CMYK value for printing representing the color determined to be outside the gamut of the printer 60 (see FIG. 1) in step 1. With respect to the value, the reference color difference A set in step 5 by the reference color difference enlargement unit 316 (see FIG. 10) corresponds to the color difference ΔE1 deviated from the gamut of the printer 60 (see FIG. 1) obtained in step 2. Enlarged by minutes.

  Here, with reference to FIG. 14, the expansion of the reference color difference in step 6 will be described.

  FIG. 14 is a diagram illustrating an example of the reference color difference A that is enlarged according to the color difference ΔE1 in Step 6. The horizontal axis indicates the color difference ΔE1 that is out of gamut of the printer 60 (see FIG. 1), and the vertical axis indicates the reference color difference.

  FIG. 14 shows a relationship in which the reference color difference A set in step 5 is enlarged by an amount corresponding to the color difference ΔE1 deviated from the gamut of the printer 60 (see FIG. 1) obtained in step 2. Yes.

  As shown in FIG. 14, if the color difference ΔE1 out of the gamut of the printer 60 (see FIG. 1) obtained in step 2 is a color that is within 1, the printer 60 ( The reference color difference A set in step S5 is adopted in the same manner as in the case of the color determined to be within the gamut in FIG. Of the color differences ΔE1 deviated from the gamut of the printer 60 (see FIG. 1) obtained in step 2, if this color difference ΔE1 is one or more, the amount corresponding to this color difference ΔE1 is the same as in step S5. The set reference color difference A is enlarged.

  Next, returning to FIG. 11, the description of the flowchart in which the device link profile 600 (see FIG. 4) is specifically modified will be continued.

Next, in the smoothing process (step S7), the smoothing processing unit 317 (see FIG. 10) applies the plurality of CMYK values for the printer in the device link profile corrected in step S3. A smoothing process for smoothing the discontinuity between the CMYK values is performed, and the device link profile after the correction in step S3 is corrected. In this smoothing process, the average value of the CMYK values of the lattice of interest in the device link profile 600 (see FIG. 4) having the LUT format and the CMYK values of surrounding lattices adjacent to the lattice is obtained. This is determined as the CMYK value of the grid to be used. When the CMYK values before the smoothing process are representatively represented (C0, M0, Y0, K0) and the function (Function) representing the smoothing process is F, the smoothing process is performed. The representative CMYK values (C1, M1, Y1, K1) are
C1 = F (C0)
M1 = F (M0)
Y1 = F (Y0)
K1 = F (K0)
It is represented by

Next, in the process of calculating the color difference ΔE2 (step S8), the reference color set in step S4 and the CMYK values (C1, M1, Y1, K1) for the printer after the smoothing process is performed in step S7. The color difference ΔE2 from the color represented by) is obtained by the color difference calculation unit 318 (see FIG. 10). Here, first, the CMYK values (C1, M1, Y1, K1) for the printer that have been subjected to the smoothing process in step S7 were used when the device link profile 600 (see FIG. 4) was created. It is converted into an L ^* a ^* b ^* value by the printer profile 500 (see FIGS. 4 and 6). Hereinafter, a representative representation of the L ^* a ^* b ^* value will be referred to as (L1, a1, b1). Next, the color represented by the L ^* a ^* b ^* value (L0, a0, b0), which is the reference color set in step S4, and the CMYK value for the printer after the smoothing process in step S7 ( The color difference ΔE2 from the color represented by the L ^* a ^* b ^* values (L1, a1, b1) corresponding to C1, M1, Y1, K1) is obtained by the following equation (3).

ΔE2 = √ (dL · dL + da · da + db · db) (3)
However,
dL = L1-L0
da = a1-a0
db = b1-b0
Next, in the process of comparing the color difference ΔE2 and the reference color difference A (step S9), the color difference ΔE2 obtained in step S8 is compared with the reference color difference A set in step S5. However, when the color difference ΔE1 obtained in step 2 is 1 or more, the reference color difference enlarged in accordance with the color difference ΔE1 in step S6 is used instead of the set reference color difference. In Step 9, both are indicated as a reference color difference A without distinguishing between the two. In comparing the color difference ΔE2 with the reference color difference A, first, the color difference ΔE2 and the reference color difference A are used, and r, which is a value of the ratio of the color difference ΔE2 to the reference color difference A, is obtained by the following equation (4).

r = ΔE2 / A (4)
Next, the magnitude of the color difference ΔE2 and the reference color difference A is compared based on the value of r thus determined. here,
r ≦ 1
In other words, that is, when the color difference ΔE2 is equal to or smaller than the reference color difference A,
r> 1
In other words, the process described below is performed separately for the case where the color difference ΔE2 is larger than the reference color difference A.

That is, in the process of correcting the CMYK value of the CMYK color space for the printer (step S10), the color difference ΔE2 obtained in step S8 is larger than the reference color difference A, and the value of r obtained by the above equation (4). R> 1
In this case, the CMYK values (C1, M1, Y1, K1) for the printer after the smoothing process is performed in step S7 correspond to the CMYK values (C1, M1, Y1, K1) for the printer. Color difference between the color represented by the L ^* a ^* b ^* value (L1, a1, b1) and the color represented by the reference color, that is, the L ^* a ^* b ^* value (L0, a0, b0) set in step S4 The coordinate point correction unit 319 (see FIG. 10) corrects so that ΔE2 becomes smaller. Here, assuming that the L ^* a ^* b ^* values after correction are representatively represented as (L1 ′, a1 ′, b1 ′), the L ^* a ^* b ^* values (L1 ′, a1 ′). , B1 ′) is obtained by the following equations (5), (6), and (7).

L1 ′ = L0 + dL / r (5)
a1 ′ = a0 + da / r (6)
b1 ′ = b0 + db / r (7)
Printer CMYK values (C1 ′, M1 ′, L1 ′, a1 ′, b1 ′) corresponding to the L ^* a ^* b ^* values (L1 ′, a1 ′, b1 ′) obtained by the above formulas (5), (6), (7). Y1 ′, K1 ′) is the CMYK value of the device link profile after correction.

Further, when the color difference ΔE2 obtained in step S8 is equal to or smaller than the reference color difference A set in step S5, or the color difference ΔE1 deviated from the gamut of the printer 60 (see FIG. 1) obtained in step 2 is obtained. For one or more colors, when the color difference ΔE2 obtained in step S8 is equal to or smaller than the reference color difference A expanded in accordance with the color difference ΔE1 in step S6, that is, the value of r obtained by the above equation (4) is r ≦ 1
In this case, the CMYK values (C1, M1, Y1, K1) that have been subjected to the smoothing process in step S7 are directly applied to the device link profile without the correction described in step S10 described above. Used as CMYK value.

  Here, referring to FIG. 15 and FIG. 16, the set reference color difference A is enlarged by an amount corresponding to the color difference ΔE1 deviating from the gamut of the printer 60 (see FIG. 1), and then the smoothing process is performed. The effect when this is done will be described.

  FIG. 15 is a diagram in which Y and M values are plotted after the CMYK halftone data is color-converted by the device link profile obtained by the smoothing process using the reference color difference A as it is set. The horizontal axis represents the dot percentage of M (Magenta) ink (gradation in which the color continuously changes from C color to B (Blue) color) with respect to the dot percentage of C (Cyan) ink being 100%. The vertical axis indicates the dot percentage of Y (Yellow: yellow) ink with respect to 100% dot percentage of C ink (gradation in which the color continuously changes from C color to R (Red) color).

  FIG. 15 shows a device link that has been subjected to a smoothing process in which the set reference color difference A is uniformly adopted even for colors that are out of the gamut of the printer 60 (see FIG. 1). An example in which the values of Y and M after color conversion by a profile are plotted is shown. In the example shown in FIG. 15, the Y ink halftone percentage is 10% or less, and the M ink halftone percentage is 10%. In the following part, the lack of gradation appears remarkably.

  FIG. 16 is a diagram in which Y and M values are plotted after CMYK halftone data is color-converted by the device link profile obtained by the smoothing process in which the reference color difference is enlarged. The horizontal axis represents the dot percentage of M (Magenta) ink (gradation in which the color continuously changes from C color to B (Blue) color) with respect to the dot percentage of C (Cyan) ink being 100%. The vertical axis indicates the dot percentage of Y (Yellow: yellow) ink with respect to 100% dot percentage of C ink (gradation in which the color continuously changes from C color to R (Red) color).

  In FIG. 16, the color based on the device link profile subjected to the smoothing process in which the set reference color difference A is enlarged by the amount corresponding to the color difference ΔE1 that is out of the gamut of the printer 60 (see FIG. 1). An example in which the values of Y and M after conversion are plotted is shown. As described above, in the example shown in FIG. 15, tone deletion is noticeably observed in the portion where the Y ink halftone is 10% or less and in the portion where the M ink halftone is 10% or less. In the example shown in FIG. 16, it can be confirmed that the gradation reproducibility is maintained by avoiding the deletion of the gradation in those portions.

  As described above, according to the color conversion definition correcting device of this embodiment and the color conversion definition correcting program that causes the computer to operate as such a color conversion definition correcting device, the inside of the gamut of the printer 60 (see FIG. 1). In this portion, the color matching accuracy is prevented from being greatly lowered, and the predetermined color matching accuracy is maintained, and in the portion outside the gamut, gradation deletion is avoided and tone reproducibility is maintained. That is, according to such a color conversion definition correcting apparatus, it is possible to achieve both color matching accuracy and gradation reproducibility at a high level.

  In the description of the present embodiment, as an example of the smoothing processing unit according to the present invention, an example in which smoothing processing is performed on the entire profile has been shown. However, the smoothing processing unit according to the present invention is a part of a profile. May be subjected to a smoothing process.

Furthermore, in the description of the present embodiment, as an example of the coordinate point correction unit referred to in the present invention, the L ^* a ^* b ^* values (L1 ′, a1 ′, b1 ′) after correction are the above (5), Although the example calculated | required by (6), (7) formula was shown, the coordinate point correction part said to this invention filters by weighting the weighting coefficient of an evaluation point, for example, and evaluates so that it may be settled in a target color difference. A point weighting coefficient may be determined, a local filter coefficient may be determined based on the determined weighting coefficient, and smoothing may be performed again using filters having different local weights.

1 is an overall configuration diagram of a printing and proof image creation system in which a device link profile modified according to an embodiment of the present invention is employed. FIG. 2 is an external perspective view of a spectrocolorimeter shown as a block in FIG. 1 and a personal computer constituting one embodiment of the color conversion definition correcting device of the present invention. FIG. 3 is a hardware configuration diagram of the personal computer shown in FIG. 2. It is explanatory drawing of profile creation and correction. It is a conceptual diagram of a printing profile. FIG. 3 is a conceptual diagram of a printer profile. FIG. 7 is a conceptual diagram of a device link profile in which the print profile shown in FIG. 5 and the printer profile shown in FIG. 6 are combined. It is the figure which plotted the value of Y and M after the halftone data represented by CMYK were color-converted with the profile after the smoothing process. It is the figure which showed one Embodiment of the color conversion definition correction program of this invention. It is a functional block diagram which shows one Embodiment of the color conversion definition correction apparatus of this invention. It is a flowchart which shows one Embodiment of the flow of a process in the color conversion definition correction apparatus of this invention. It is a figure which shows the example of the weight employ | adopted according to color difference (DELTA) E1 in the case of the synthesis | combination in step 3. FIG. FIG. 6 is a diagram in which Y and M values are plotted after halftone data represented by CMYK is color-converted by the device link profile subjected to the above correction. It is a figure which shows the example of the reference | standard color difference A expanded in step 6 according to color difference (DELTA) E1. FIG. 10 is a diagram in which Y and M values after color conversion of CMYK halftone data is performed by a device link profile obtained by a smoothing process using a reference color difference A that has been set. FIG. 5 is a diagram in which Y and M values after color conversion of CMYK halftone data is performed by a device link profile obtained by a smoothing process in which a reference color difference is enlarged;

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color scanner 11 Original image 20 Workstation 30 Film printer 40 Printing machine 41 Print image 42, 43, 62, 63, 64, 90 Color chart 50 Personal computer 60 Printer 61 Proof image 70 Spectral colorimeter 80 Personal computer 81 Main unit 81a FD loading port 81b CD-ROM loading port 811 CPU
812 Main memory 813 Hard disk device 814 FD drive 815 CD-ROM drive 816 I / O interface 82 Image display device 82a Display screen 83 Keyboard 84 Mouse 85 Bus 91 Cable 100 FD
110 CD-ROM
210 Color Conversion Definition Correction Program 211 Determination Unit 212 Deviation Degree Calculation Unit 213 Color Conversion Definition Correction Unit 214 Reference Color Setting Unit 215 Reference Color Difference Setting Unit 216 Reference Color Difference Enlargement Unit 217 Smoothing Processing Unit 218 Color Difference Calculation Unit 219 Coordinate Point Correction Unit 300 Color conversion definition correction device 311 determination unit 312 deviation degree calculation unit 313 color conversion definition correction unit 314 reference color setting unit 315 reference color difference setting unit 316 reference color difference enlargement unit 317 smoothing processing unit 318 color difference calculation unit 319 coordinate point correction unit 400 printing Profile 500 Printer profile 600 Device link profile

Claims (6)

The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points of the first color space and the second color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated by the color conversion definition with respect to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree determined by the deviation degree calculation unit. A conversion definition correction section;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A color conversion definition correction apparatus comprising: a smoothing processing unit that corrects the color conversion definition. The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points of the first color space and the second color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A reference color setting unit that receives a reference color for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the deviation degree calculation unit;
A smoothing processing unit that corrects the color conversion definition by performing a smoothing process for smoothing discontinuity between the coordinate points of the second color space in the color conversion definition. When,
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after being smoothed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, the smoothing processing unit performs the smoothing process A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. Color conversion definition correction device. The relationship of coordinate transformation between the first color space depending on the first device and the second color space depending on the second device is expressed as a plurality of coordinate points of the first color space and the second color space. In a color conversion definition correcting device that corrects a color conversion definition defined by associating a plurality of coordinate points of a color space with a one-to-one correspondence,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated by the color conversion definition with respect to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree determined by the deviation degree calculation unit. A conversion definition correction section;
A reference color setting unit that receives a reference color for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the deviation degree calculation unit;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A smoothing processing unit for correcting the color conversion definition;
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after being smoothed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, the smoothing processing unit performs the smoothing process A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. Color conversion definition correction device. Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on a first device and a second color space dependent on a second device. A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in the second color space in a one-to-one correspondence. There,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated by the color conversion definition with respect to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree determined by the deviation degree calculation unit. A conversion definition correction section;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A color conversion definition correction program, comprising: a smoothing processing unit that corrects the color conversion definition. Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on a first device and a second color space dependent on a second device. A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in the second color space in a one-to-one correspondence. There,
A reference color setting unit that receives a reference color for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the deviation degree calculation unit;
A smoothing processing unit that corrects the color conversion definition by performing a smoothing process for smoothing discontinuity between the coordinate points of the second color space in the color conversion definition. When,
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after being smoothed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, the smoothing processing unit performs the smoothing process A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. Conversion definition modification program. Executed in a computer, the computer is configured to determine a relationship of coordinate transformation between a first color space dependent on a first device and a second color space dependent on a second device. A color conversion definition correction program that operates as a color conversion definition correction device that corrects a color conversion definition that defines a plurality of coordinate points in a color space and a plurality of coordinate points in the second color space in a one-to-one correspondence. There,
A determination unit that determines the inside and outside of a color range that can be reproduced by the second device for the color represented by the coordinate point of the first color space in the color conversion definition;
For a color determined to be out of the color range by the determination unit, an outlier calculation unit for obtaining a degree out of the color range;
By correcting the coordinate point of the second color space associated by the color conversion definition with respect to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit The color conversion definition is corrected by combining the coordinate conversion defined by the color conversion definition with a coordinate conversion that is more linear than the coordinate conversion in accordance with the degree determined by the deviation degree calculation unit. A conversion definition correction section;
A reference color setting unit that receives a reference color for the coordinate point of the second color space in the color conversion definition;
A reference color difference setting unit for receiving an arbitrary reference color difference setting;
The reference color difference set by the reference color difference setting unit for the coordinate point of the second color space corresponding to the coordinate point of the first color space representing the color determined to be out of the color range by the determination unit. , A reference color difference enlargement unit that enlarges by an amount corresponding to the degree obtained by the deviation degree calculation unit;
A smoothing process for smoothing discontinuities between the coordinate points of the second color space in the color conversion definition after being corrected by the color conversion definition correcting unit is performed. A smoothing processing unit for correcting the color conversion definition;
A color difference calculation unit for obtaining a color difference between the reference color set by the reference color setting unit and the color represented by the coordinate point of the second color space after being smoothed by the smoothing processing unit;
After the color difference obtained by the color difference calculation unit is larger than the reference color difference with respect to the coordinate point of the second color space when the color difference is obtained, the smoothing processing unit performs the smoothing process A coordinate point correcting unit that corrects the coordinate point of the second color space so that the color difference between the color represented by the coordinate point of the second color space and the reference color is small. Conversion definition modification program.

Images