JP4853270B2 - Color gamut generation device, color gamut generation method, and color gamut generation program - Google Patents

Description

  The present invention relates to a color gamut generation device, a color gamut generation method, and a color gamut generation program. More specifically, the present invention relates to a color image signal when color reproducible areas of color image signals on the input side and output side are different. The present invention relates to a color gamut generation device, a color gamut generation method, and a color gamut generation program that generate a color gamut that is a basis for performing color conversion processing.

  Examples of devices that output color images include display devices such as CRTs and color LCDs, and printing devices such as printers. In these output devices, the reproducible color range, that is, the color gamut differs depending on the difference in each output method. For this reason, for example, when an image created on a CRT is printed by a printer, if output is performed using the same image data with different output devices, colors that cannot be reproduced may occur. In such a case, at least a color that cannot be reproduced is replaced with a color that is considered to be the closest, and the entire image can be reproduced with the best image quality in the output device. At this time, it is necessary to perform color mapping, that is, color conversion processing, in which a given color image signal is replaced with a color within the color gamut of the output device.

  In order to perform such color conversion processing, it is necessary to determine whether or not the color of the input image signal is within the color gamut of the output device, and the color gamut of the output device must be obtained.

  In Patent Document 1, a boundary color of a color gamut expressed by components of Y (yellow), M (magenta), and C (cyan) is determined, and a K (black) component is changed from the determined boundary color. A technique for creating a color gamut by acquiring a color locus is disclosed.

  Further, Patent Document 2 estimates a color mixture using a corrected primary color, and sets each color mixture using a correction coefficient determined based on a difference between an actually measured patch color and an estimated patch color. A technique for correcting and predicting a color gamut based on the corrected mixed color is disclosed.

Further, in Patent Document 3, in order to form a color gamut corresponding to the total color material amount limit, vertices constituting the color gamut outline and points on each axis connecting the vertices are extracted. A technique for extracting points with uneven allocation is disclosed.
JP 2000-101863 A Japanese Patent Application Laid-Open No. 2004-64544 JP 2005-63093 A

  However, in the inventions described in Patent Document 1 and Patent Document 2, there is a mismatch in the correspondence between the accuracy of the created color gamut and the number of polygons constituting the color gamut outline, There have been problems such as an increase in the amount of data and a decrease in compression / mapping speed.

  FIG. 7 shows an example in which a part of the color gamut 100 in the Lab color space, which is a device-independent color space, is divided into a plurality of polygons 102. In this example, two division points 104 are provided on the B-M line connecting the maximum saturation point of the main color B and the maximum saturation point of the main color M, and the B-M line is divided into three. The region on the high brightness side and the region on the low brightness side from the −M line are also divided into a plurality of polygons by the common division point 104. In this way, when the high brightness side area and the low brightness side area are divided in the same way, particularly in the case of a printer, the size of each polygon in the low brightness side area is reduced as shown in FIG. There are problems such as a problem in the shape of the color gamut outline and an increase in the data amount of the color gamut outline information due to an increase in the number of polygons.

  In the invention described in Patent Document 3, a low brightness area of a color gamut can be created with high precision, but there is a problem that it is difficult to unevenly assign points on each axis. .

  The present invention has been made to solve the above problems, and provides a color gamut generation device, a color gamut generation method, and a color gamut generation program for generating a color gamut that enables high-precision and high-speed color conversion. The purpose is to provide.

In order to achieve the above object, the color conversion apparatus according to the first aspect of the present invention provides a method for dividing an outer surface of a device color gamut in a predetermined color space into a plurality of polygons based on division number setting information. Setting means for setting the number of divisions for each divided region obtained by dividing the color gamut into at least one of the brightness direction and the hue angle direction, and dividing the outer surface by the number of divisions set for each divided region. Generating means for generating outline information of the color gamut.

According to the present invention, the number of divisions when dividing the outer surface of the device color gamut into a plurality of polygons is set for each divided region obtained by dividing the color gamut into a plurality of at least one of the brightness direction and the hue angle direction , Since the outline information of the color gamut is generated by dividing the outline surface by the division number set for each division area, the division number can be appropriately set for each division area. Accordingly, the color gamut outline can be generated with high accuracy, and color conversion can be performed at high speed when color conversion is performed using the generated color gamut outline information.

  In addition, as described in claim 2, the division number setting information uses device characteristic information of the device, device type information of the device, use purpose information of the generated color gamut, and a generated color gamut. It can be configured to include at least one of the image characteristic information of the input image to be color-converted.

  According to a third aspect of the present invention, the device characteristic information includes information related to at least one of saturation and brightness of a predetermined color in the color gamut of the device, halftone characteristic information of the predetermined color, and the It can be set as the structure which is the information containing at least 1 of the information regarding the volume of a color gamut.

  According to a fourth aspect of the present invention, the device type information may be information indicating that the device is any one of a monitor, a scanner, and a printer.

  The use purpose information includes a color gamut display process for displaying the color gamut, a color conversion coefficient creation process for creating a color conversion coefficient for color conversion, and an input image signal whose color is Any of the color gamut warning processes that warn of out-of-gamut may be information indicating that the purpose of use of the color gamut of the device is information.

According to a sixth aspect of the present invention , in the case where the divided region is a region divided in the hue angle direction, the setting means sets the number of divisions based on the hue angle between adjacent main colors. be able to.

According to a seventh aspect of the present invention, when the color gamut is divided into a high brightness side region and a low brightness side region and the vertexes of the polygons at the boundary between the two regions do not match, the setting means The polygon can be further divided so that the vertices coincide.

The color gamut generation method according to an eighth aspect of the present invention is based on the division number setting information, and determines the division number when dividing the outer surface of the device color gamut in a predetermined color space into a plurality of polygons. Is set for each of the divided areas divided into at least one of the lightness direction and the hue angle direction, and the outline information of the color gamut is generated by dividing the outline surface by the number of divisions set for each of the divided areas. Features.

According to the present invention, the number of divisions when dividing the outer surface of the device color gamut into a plurality of polygons is set for each divided region obtained by dividing the color gamut into a plurality of at least one of the brightness direction and the hue angle direction , Since the outline information of the color gamut is generated by dividing the outline surface by the division number set for each division area, the division number can be appropriately set for each division area. Accordingly, the color gamut outline can be generated with high accuracy, and color conversion can be performed at high speed when color conversion is performed using the generated color gamut outline information.

The color gamut generation program according to the invention described in claim 9 sets the number of divisions when dividing the outer surface of the device color gamut in a predetermined color space into a plurality of polygons based on the division number setting information. Is set for each of the divided areas divided into at least one of the brightness direction and the hue angle direction, and the outline information of the color gamut is generated by dividing the outline surface by the number of divisions set for each of the divided areas. And causing the computer to execute a process including the steps.

According to the present invention, the number of divisions when dividing the outer surface of the device color gamut into a plurality of polygons is set for each divided region obtained by dividing the color gamut into a plurality of at least one of the brightness direction and the hue angle direction , Since the outline information of the color gamut is generated by dividing the outline surface by the division number set for each division area, the division number can be appropriately set for each division area. Accordingly, the color gamut outline can be generated with high accuracy, and color conversion can be performed at high speed when color conversion is performed using the generated color gamut outline information.

  As described above, according to the present invention, there is an effect of generating a color gamut that enables color conversion with high accuracy and high speed.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

  First, a schematic configuration of the color conversion device will be described. FIG. 1 is a block diagram showing a schematic configuration example of a color conversion apparatus according to the present invention. The color conversion apparatus described here is mounted on an image output apparatus such as a digital copying machine or a printer, or is mounted on a server apparatus connected to the image output apparatus, or a computer that gives an operation instruction to the image output apparatus ( Driver device) is used.

  As shown in the figure, the color conversion apparatus 10 includes an input color space conversion unit 12, a color conversion unit 14, an output color space conversion unit 16, a color gamut generation unit 18, a division number setting information output unit 20, and a memory 22. It has.

  The input color space conversion unit 12 converts an input image signal dependent on the input side device into a device-independent image signal based on the input profile. Examples of the input image signal include a color image signal in an RGB color space for display on a CRT or the like, and a color image signal in a CMYK color space. Examples of device-independent image signals include color image signals in the Lab color space and color image signals in the JCH color space.

  The color conversion unit 14 is device-independent from the input color space conversion unit 12 based on the color gamut outline information in the device-independent color space of the input side device and output side device generated by the color gamut generation unit 18. The input image signal is color-converted and output to the output color space conversion unit 16. Various known methods can be used for the color conversion method.

  The output color space conversion unit 16 converts the device-independent image signal color-converted by the color conversion unit 14 into an output image signal dependent on the output device based on the output profile, and outputs the output image signal. Examples of the output image signal include a color image signal in a CMY color space or a CMYK color space for printing on a printer or the like. In the present embodiment, a case where the output image signal is a color image signal in the CMYK color space will be described.

  Although the details will be described later, the color gamut generation unit 18, based on the division number setting information output from the division number setting information output unit 20, the device-independent color space of the input side device and the output device, for example, Color gamut outline information representing the color gamut outline in the Lab color space is generated and output to the color converter 14.

  The division number setting information output unit 20 includes, for example, device characteristic information of the input side device and the output side device, device type information of the input side device and the output side device, use purpose information of the generated color gamut, and the generated color gamut. The division number setting information including at least one of the image characteristic information of the input image used for color conversion is output to the color gamut generation unit 18. The division number setting information, which will be described in detail later, is information necessary for generating device color gamut outline information. For example, the division number setting information is stored in advance or an input profile indicating color reproduction characteristics of the input side device, This information is generated based on an output profile or the like representing the color reproduction characteristics of the output side device.

  Each of these units 12 to 22 includes, for example, an image output device, a server device, or a driver device, and includes a combination of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Each of the computers can be realized by executing a predetermined program.

  Next, a processing routine executed by the color gamut generation unit 18 will be described with reference to a flowchart shown in FIG.

  First, in step 100, device type information of a device for which color gamut outline information is to be generated is requested and acquired from the division number setting information output unit 20, and the device is set. For example, when the device for generating the color gamut outline information is a CMYK printer, the printer is set as the printer for generating the color gamut outline information. Hereinafter, a case where a CMYK printer is set will be described. Note that a device that generates color gamut outline information may be designated by a user operation.

  In step 102, the division number setting information output unit 20 is requested and acquired for use purpose information, and the standard division for dividing the color gamut outline into a plurality of polygons (polygonal regions) according to the obtained use purpose information. Set the number. The purpose of use information is information indicating what purpose the color conversion device 10 is used for. Accordingly, the standard division number is set for each purpose of use.

  Here, the standard number of divisions may be expressed by the total number of polygons 32 when the outer surface of the color gamut 30 in the Lab space of a certain device is divided into a plurality of polygonal polygons 32 as shown in FIG. Alternatively, for example, it may be expressed by the number of divisions of the main color lines by the division points provided on the main color lines 34 connecting the main colors (Y, M, C, R, G, B). The number is not limited to these as long as the number can be expressed.

  For example, when used for high-speed color gamut display processing that displays the color gamut of a desired device at high speed, color conversion according to the intent indicating the characteristics of color reproduction or color according to the type of device When used for color conversion coefficient creation processing that creates color conversion coefficients for conversion, when used for color gamut warning processing that determines whether or not the input image signal is within the color gamut and warns when it is out of the color gamut However, it is not limited to this.

  For example, when used for color gamut high-speed display processing, to increase the display speed of the color gamut in order to increase the display speed of the color gamut, the standard division number is smaller than a predetermined reference division number. Set to a suitable number. Note that the reference division number is, for example, an average division number of standard division numbers for every purpose of use.

  In addition, when used for color conversion coefficient creation processing, it is required to perform color conversion with high accuracy, so the standard division number is larger than the reference division number and suitable for color conversion with high accuracy. Set to a number.

  Further, when used for color gamut warning processing, it is only necessary to know whether or not the input image signal is within the color gamut. Therefore, in this case, the standard division number is set to a number smaller than the reference division number and suitable for determining whether or not the input image signal is in the color gamut.

  In this embodiment, the standard division number is set for each purpose of use, but the standard division number may be set as the reference division number regardless of the purpose of use.

  In step 104, device characteristic information is requested and acquired from the division number setting information output unit 20. Here, for example, data of maximum saturation and minimum brightness (K) of main colors (Y, M, C, R, G, B) is acquired as device characteristic information. The division number setting information output unit 20 may store and store these data in advance, or may calculate from the profile data representing the characteristics of the device.

  In step 106, the division number is set for each divided area obtained by dividing the color gamut outline into a plurality of divided areas based on the acquired device characteristic information. Here, the color gamut is divided into two divided areas of a high brightness side area and a low brightness side area, and the number of divisions of the low brightness side area is set to be smaller than the number of divisions of the high brightness side area. The high brightness side area is an area having a brightness higher than the brightness of the maximum saturation point of the main colors (Y, M, C, R, G, B), for example, and the low brightness side area is a high brightness area. This is an area other than the degree side area, that is, an area having a lightness equal to or lower than the lightness of the maximum saturation point of the main color.

  The number of divisions is set as follows, for example. First, the average lightness of the maximum saturation point of each main color is obtained, and the difference Li between the average lightness and the minimum lightness of the maximum saturation point of each main color is obtained. Then, the difference Li is compared with a predetermined reference difference Lb, and the division number DL of the low brightness side region is set based on the comparison result. For example, when Li ≧ Lb, that is, when the size of the low brightness side region is not so small, the standard division number is set to DS, and DL = DS × C. However, C is a division coefficient and is an arbitrary number of C <1. That is, the division number DL is set to a number smaller than the standard division number DS. On the other hand, when Li <Lb, that is, when the size of the low brightness side region of the color gamut is small, DL = DS × C × (Li / Lb). Here, since Li / Lb is a value less than 1, the division number DL is set to a smaller number than in the case of Li ≧ Lb. Note that the division number DH of the high brightness side region is set to the standard division number DS. The division number DH of the high brightness side region may be set based on the maximum saturation of the main color. For example, the division number may be increased as the maximum saturation is higher, and the division number may be decreased as the maximum saturation is lower.

  For example, in the example of FIG. 3, for the high brightness side region 30A, two division points 36A are set on the B-M line connecting the main color B and the main color M, and the number of divisions of the high brightness side region 30A is set to 3. For the low brightness side region 30B, one division point 36B is set on the B-M line, and the number of divisions of the low brightness side region 30B is set to two.

In step 108, the color gamut outline is divided into a plurality of polygons according to the division number set for each division area, and color gamut outline information is generated. This color gamut outline information may be, for example, information representing the correspondence between each polygon and the brightness and saturation data (each value of L, a ^* , b ^* ) of each vertex of the polygon. It may be information including lightness and saturation data and connection information indicating how each vertex is connected, that is, which vertex is connected to which vertex.

  The vertices of each polygon can be set by, for example, selecting from a large number of outline point groups constituting the outline of the color gamut. The outline point group data may be obtained in advance based on device profile data, for example, and stored in the memory 22 in advance, or may be obtained each time. Various known methods can be used as a method for obtaining the data of the outline point group.

  In step 110, the generated color gamut outline information is output to the color conversion unit 14. The processing of this routine is performed for each of the input side device and the output side device to generate color gamut outline information and output the color gamut outline information to the color conversion unit 14. The input image signal can be converted into an image signal in the color gamut of the output device and output.

  As described above, when the device is a CMYK printer, the color gamut outline information is generated by making the number of divisions of the low brightness side area smaller than the number of divisions of the high brightness side area, so that the shape of the color gamut outline on the low brightness side is obtained. It is possible to prevent a problem from occurring or an increase in the number of polygons and an increase in the data amount of color gamut outline information.

  In the above description, when the device is a CMYK printer, the number of polygon divisions is different between the high brightness side area and the low brightness side area, but the color gamut depends on the degree of the K (black) component included. May be divided into a plurality, and the number of divisions may be set for each region. For example, as shown in FIG. 4, the color gamut includes a first region 40 (high brightness side region) with K = 0%, a second region 42 with 0 <K <100%, and a third region with K = 100%. The area 44 is divided so that the division number of the first area 40 is D1, the division number of the second area 42 is D2, and the division number of the third area 44 is D3 so that D1> D2> D3. Set the number of divisions. That is, the number of divisions is set to be smaller as the brightness becomes lower. As a result, it is possible to effectively prevent the occurrence of problems in the shape of the color gamut outline on the low brightness side.

  Also, for example, in step 104, information on the color gamut volume is acquired as device characteristic information, the volumes of the high brightness side region and the low brightness side region are compared, the larger number of divisions is larger, and the smaller volume is smaller. The number of divisions may be reduced.

  Further, depending on the image characteristics of the input image, for example, the type of image, there are a type in which the generated color gamut outline needs to be generated with high accuracy and a type in which it is not necessary to generate with high accuracy. Therefore, for example, the image characteristic information of the input image may be acquired as the device characteristic information in step 104, and the division number may be set according to the image characteristic of the input image. For example, when the input image is a photograph, since there is little data in the vicinity of the color gamut outline, it is not necessary to generate the color gamut outline with such high accuracy. For this reason, when the image characteristic information indicates that the input image is a photograph, the division number is set to a smaller number than usual. Further, when the input image is graphics, there are a lot of data in the vicinity of the color gamut outline, so it is necessary to generate the color gamut outline with high accuracy. For this reason, when the image characteristic information indicates that the input image is graphics, the division number is set to a larger number than usual. In addition, the image characteristic information may include information on a region that is mainly used in the color gamut and a region that is not frequently used. In this case, the number of divisions may be set large for a region that is mainly used, and the number of divisions may be set small for a region that is not often used.

  Further, for example, in step 104, a halftone characteristic of a main color, for example, a γ characteristic (gradation curve) may be acquired as device characteristic information, and the division number may be set based on the γ characteristic. For example, the number of divisions may be set to be larger as the area has a steep gradation curve, and the number of divisions may be set to be smaller as the area has a gentle gradation curve.

Further, when the polygon division numbers are made different between the high lightness side region and the low lightness side region, the vertexes of the polygons at the boundary between the high lightness side region 30A and the low lightness side region 30B may not match. For example, as shown in FIG. 3, the vertex 36B of the polygon 32B in the low brightness side region 30B at the boundary is not connected to any vertex of the polygon 32A in the high brightness side region 30A and is positioned on the side of the polygon. Yes. In this case, there is a particular problem when the color gamut outline information is information representing the correspondence between each polygon and the brightness and saturation data (each value of L, a ^* , b ^* ) of each polygon. Absent. However, the color gamut outline information is information including the lightness and saturation data of each vertex and connection information indicating how each vertex is connected, that is, which vertex is connected to which vertex. In such a case, as described above, it is not possible to divide the polygon so that the vertex of the polygon is positioned on the side of another polygon. Therefore, in such a case, the polygon 32A is further divided as shown in FIG. 5 by the line 38A connecting the vertex 36B on the side of the polygon 32A and the vertex of the polygon 32A. Similarly, for the vertex 36A, the polygon 32B is further divided by a line 38B connecting the vertex 36A and the vertex of the polygon 32B. Thereby, the vertices of all the polygons can be connected.

  In the above description, the case where the device is a CMYK printer has been described. However, when the device is a monitor, for example, unlike the printer, there is little problem in the shape of the color gamut outline on the low brightness side. For this reason, when the device is a printer, the high brightness side area and the low brightness side area may be the same without changing the number of polygon divisions.

  Further, when the device is a scanner, it is necessary to generate a color gamut outline of a highlight area having a high brightness among the high brightness side areas with high accuracy. For this reason, as shown in FIG. 6, the highlight area 50 may be divided more finely than the other areas.

  In the above description, the case where the number of divisions is varied in the brightness direction has been described. However, the number of divisions may be varied in the hue direction. In this case, steps 100 and 102 in FIG. 2 perform the same processing as described above, and in step 104, for example, the maximum saturation and hue of the main colors (Y, M, C, R, G, and B) as device characteristic information. Get the data. Then, the average value of the maximum saturation between the adjacent main colors is obtained from the maximum saturation data of each main color. For example, the average value of the maximum saturation of Y and G is C_YG, the average value of the maximum saturation of G and C is C_GC, the average value of the maximum saturation of C and B is C_CB, and the average of the maximum saturation of B and M The value is C_BM, the average value of the maximum saturation of M and R is C_MR, and the average value of the maximum saturation of R and Y is C_RY. Then, the average value of the maximum saturation of each main color is set as the reference saturation.

  Further, an average value of hue angles between adjacent main colors is obtained from the hue data of each main color. For example, the hue angle between YG is Hd_YG, the hue angle between GC is Hd_GC, the hue angle between CB is Hd_CB, the average value of the hue angle maximum saturation between BM is Hd_BM, and the hue angle between MR is between Hd_MR and RY. Is set to Hd_RY. Then, an average value of hue angles between the main colors is set as a reference hue angle.

  Then, in step 106, for each of the regions between adjacent main colors, that is, each of the region between YG, the region between GC, the region between CB, the region between BM, the region between MR, and the region between RY. For example, the number of divisions can be set as follows, but the method of setting the number of divisions is not limited to this. For example, for the area between YG, for example, when C_YG is smaller than the reference saturation, the area between YG is divided by a division number smaller than the standard division number. When C_YG is greater than the reference saturation and Hd_YG is greater than the reference hue angle, the region between YG is divided by a division number larger than the standard division number. When C_YG is larger than the reference saturation and Hd_YG is smaller than the reference hue angle, the region between YG is divided by the standard division number. When Hd_YG is larger than the reference hue angle, the region between YG is divided by a division number larger than the standard division number. The same applies to other regions. In this way, the number of divisions may be varied in the hue direction instead of the number of divisions in the brightness direction.

  After setting the number of divisions in this way, color gamut outline information is created in step 108, and color gamut outline information is output to the color conversion unit 14 in step 110.

  As described above, in this embodiment, the number of divisions is set for each divided region obtained by dividing the color gamut into a plurality of regions, and each divided region is divided into a plurality of polygons to generate color gamut outline information. It is possible to suppress a decrease in color conversion speed and a decrease in color conversion accuracy due to an increase in the number.

It is a schematic block diagram of a color conversion apparatus. It is a flowchart of the process performed in a color gamut generation part. It is a figure which shows the example of a division | segmentation of a color gamut outline. It is a figure for demonstrating the division | segmentation of a color gamut outline. It is a figure which shows the example of a division | segmentation of a color gamut outline. It is a figure which shows the example of a division | segmentation of a color gamut outline. It is a figure which shows the example of a division | segmentation of the conventional color gamut outline.

Explanation of symbols

10 color conversion device 12 input color space conversion unit 14 color conversion unit 16 output color space conversion unit 18 color gamut generation unit 20 division number setting information output unit 22 memory 30 color gamut 30A high brightness side region 30B low brightness side region 32 polygon

Claims (9)

Based on the division number setting information, the division number when dividing the outer surface of the device color gamut in a predetermined color space into a plurality of polygons is divided into at least one of the lightness direction and the hue angle direction. Setting means for setting each divided area;
Generating means for generating outline information of the color gamut by dividing the outline surface by a division number set for each of the divided areas;
A color gamut generating device.   The division number setting information includes at least device characteristic information of the device, device type information of the device, usage purpose information of the generated color gamut, and image characteristic information of an input image to be color-converted using the generated color gamut. The color gamut generation device according to claim 1, comprising one.   The device characteristic information includes at least one of information on at least one of saturation and brightness of a predetermined color in the color gamut of the device, halftone characteristic information on the predetermined color, and information on the volume of the color gamut. The color gamut generation device according to claim 2, wherein the information includes information.   3. The color gamut generating apparatus according to claim 2, wherein the device type information is information indicating that the device is any one of a monitor, a scanner, and a printer.   The usage purpose information includes a color gamut display process for displaying the color gamut, a color conversion coefficient creation process for creating a color conversion coefficient for color conversion, and a color gamut warning process for warning that the input image signal is out of the color gamut. The color gamut generating apparatus according to claim 2, wherein any of the information is information indicating that the color gamut of the device is used. For regions where the dividing area is split hue angle direction, the setting means, any claims 1 to 5, characterized in that setting the number of divisions based on the hue angle of the adjacent major colors The color gamut generation device according to claim 1. When the color gamut is divided into a high lightness side region and a low lightness side region and the vertices of the polygons at the boundary between the two regions do not match, the setting means further sets the polygons so that the vertices of the polygons match. gamut generating apparatus according to any one of claims 1 to 6, characterized in that split. Based on the division number setting information, the division number when dividing the outer surface of the device color gamut in a predetermined color space into a plurality of polygons is divided into at least one of the lightness direction and the hue angle direction. Set for each divided area,
A color gamut generation method for generating outline information of the color gamut by dividing the outline surface by a division number set for each of the division areas. Based on the division number setting information, the division number when dividing the outer surface of the device color gamut in a predetermined color space into a plurality of polygons is divided into at least one of the lightness direction and the hue angle direction. A step for setting each divided area;
Generating the outline information of the color gamut by dividing the outline surface by the division number set for each of the division areas;
A gamut generation program for causing a computer to execute processing including the above.

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