JP3988012B2 - Color conversion method, color conversion device, and recording medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color conversion method, a color conversion apparatus, and a recording medium when an output color reproduction region is narrower than an input color reproduction region.
[0002]
[Prior art]
When the monitor image signal is hard-copied using a printer or the like, color conversion is necessary because each color system is different.
[0003]
That is, the monitor image is a color image formed by the additive color method, and the RGB color coordinate system of the phosphor is used as the color system. On the other hand, a color image is formed by a subtractive color method on photographic paper and the like, and a color system such as L ^* a ^* b ^* is used as the color system. In such a case, it is necessary to convert signal data (color correction) between these color systems.
[0004]
[Problems to be solved by the invention]
However, for example, when a color reproduction area such as photographic paper and a color reproduction area such as color CRT are represented by the same color system such as L ^* a ^* b ^* , these color reproduction areas for this color system Are generally different. For example, when the color CRT is the input color system and the photographic paper is the output color system, the color reproduction area of the output color system is narrower than the color reproduction area of the input system.
[0005]
For this reason, when color image information exceeding the color reproduction region of the output color system is input, there is no output color system value corresponding thereto. As a result, conventionally, color correction data relating to color image information that exceeds the color reproduction area of the output color system has been appropriately compressed into the color reproduction area, so that the hue, saturation, or lightness is human visual characteristics. It has changed in a different direction and was very unnatural. In particular, the shape of the color reproduction region varies depending on the hue. For example, when the blue color of the display is reproduced by a printer, it is preferable to reproduce it while keeping the brightness higher. On the other hand, when the green of the display is reproduced by a printer, it is preferable that the brightness is lowered and the saturation is reproduced as high as possible. That is, it is necessary to perform color conversion in consideration of a change in the color reproduction region due to a change in hue angle.
[0006]
The present invention has been made in order to solve the above-described problems. When color correction data relating to color image information exceeding the color reproduction area of the output color system is compressed into the color reproduction area, a more faithful color is provided. It is an object to provide a color conversion method, a color conversion device, and a recording medium that can be reproduced.
[0007]
[Means for Solving the Problems]
In view of the above problems, the invention according to claim 1 is such that when the color reproduction region of the output system is narrower than the color reproduction region of the input system, the color reproduction of the output system is within the color reproduction region of the input system. A color conversion method when color image information outside a region is input, and for a cross section including an achromatic color axis of a color system at a predetermined hue angle, the coordinate axis indicating lightness is L, and the coordinate axis indicating saturation is C , A setting step for setting arbitrary coordinates on the CL plane to (l, c), and points corresponding to color image information outside the color reproduction area of the output system in the achromatic direction of the output color system. A change step of changing the value of a or b according to the predetermined hue angle when compressing using = ac + b (a is an inclination, and b is an intersection with an achromatic color L-axis). The
[0008]
When the color reproduction area of the output system configured as described above is narrower than the color reproduction area of the input system, the color image information within the color reproduction area of the input system and outside the color reproduction area of the output system is According to the color conversion method at the time of input, first, in the setting step, regarding the cross section including the achromatic color axis of the color system at a predetermined hue angle, the coordinate axis indicating brightness is L and the coordinate axis indicating saturation is C In addition, arbitrary coordinates on the CL plane are set to (l, c). Then, by the changing step, the point corresponding to the color image information outside the color reproduction area of the output system is changed to l = ac + b (a is an inclination, b is an intersection with the L axis of the achromatic color) in the achromatic direction of the output color system. ), The value of a or b is changed according to the predetermined hue angle.
[0009]
The invention according to claim 2 is the color conversion method according to claim 1, wherein the predetermined hue angle and two colors on both sides of the color corresponding to the predetermined hue angle are displayed on the hue surface. Based on the difference from the hue angle of the basic color, the value a or b is changed.
[0010]
Further, the invention according to claim 3 is the color conversion method according to claim 1, wherein the predetermined hue angle is θi, and hues of two basic colors on both sides of the color corresponding to the predetermined hue angle. When the angles are θr and θy (θr <θi <θy), and the values of the coefficients a and b at the hue angles θr and θy are ar, br, ay, and by, respectively, the values of the coefficients a and b at the hue angle θi The
a = (ar × (θy−θi) + ay × (θi−θr)) / (θy−θr)
b = (br × (θy−θi) + by × (θi−θr)) / (θy−θr)
Calculated by
[0011]
In view of the above problems, in the invention according to claim 4, when the color reproduction area of the output system is narrower than the color reproduction area of the input system, the color reproduction of the output system is within the color reproduction area of the input system. A color conversion apparatus when color image information outside a region is input, and for a cross section including an achromatic color axis of a color system at a predetermined hue angle, L is a coordinate axis indicating brightness, and C is a coordinate axis indicating saturation. , Setting means for setting an arbitrary coordinate on the CL plane to (l, c), and a point corresponding to color image information outside the color reproduction area of the output system in the achromatic direction of the output color system. Changing means for changing the value of a or b according to the predetermined hue angle when compression is performed using = ac + b (a is an inclination, and b is an intersection with an achromatic color L-axis). The
[0012]
When the color reproduction area of the output system configured as described above is narrower than the color reproduction area of the input system, the color image information within the color reproduction area of the input system and outside the color reproduction area of the output system is According to the color conversion apparatus when input, first, the setting means sets the coordinate axis indicating lightness to L and the coordinate axis indicating saturation to C for a cross section including the achromatic color axis of the color system at a predetermined hue angle. , Arbitrary coordinates on the CL plane are set to (l, c). Then, by the changing means, the point corresponding to the color image information outside the color reproduction area of the output system is changed to l = ac + b (a is an inclination, b is an intersection with the L axis of the achromatic color) in the achromatic direction of the output color system. ), The value of a or b is changed according to the predetermined hue angle.
[0013]
The invention according to claim 5 is the color conversion device according to claim 4, wherein on the hue surface, the two basics of the predetermined hue angle and both sides of the color corresponding to the predetermined hue angle are provided. Based on the difference from the hue angle of the color, the value of a or b is changed.
[0014]
Further, the invention according to claim 6 is the color conversion apparatus according to claim 4, wherein the predetermined hue angle is θi, and the hue angles of two basic colors on both sides of the color corresponding to the predetermined hue angle. Are θr and θy (θr <θi <θy), and the values of the coefficients a and b at the hue angles θr and θy are respectively ar, br, ay, and by, the values of the coefficients a and b at the hue angle θi are
a = (ar × (θy−θi) + ay × (θi−θr)) / (θy−θr)
b = (br × (θy−θi) + by × (θi−θr)) / (θy−θr)
Calculated by
[0015]
In view of the above problems, the invention according to claim 7 is such that, when the color reproduction region of the output system is narrower than the color reproduction region of the input system, the color reproduction of the output system is within the color reproduction region of the input system. A computer-readable recording medium storing a program for causing a computer to execute color conversion processing when color image information outside the area is input, wherein an achromatic color axis of a color system at a predetermined hue angle A setting process for setting a coordinate axis indicating lightness to L, a coordinate axis indicating saturation to C, and an arbitrary coordinate on the CL plane to (l, c), and a color outside the color reproduction region of the output system with respect to the included cross section. The point corresponding to the image information is set to l = ac + b in the achromatic direction of the output color system (a is an inclination, and b is an intersection with the achromatic L axis)
When the compression is performed, a program for causing the computer to execute a changing process for changing the value of a or b in accordance with the predetermined hue angle is configured to be readable by the computer.
[0016]
In the computer-readable recording medium configured as described above, when the output system color reproduction region is narrower than the input system color reproduction region, the output system is within the input system color reproduction region. A program for causing a computer to execute color conversion processing when color image information outside the color reproduction area is input is recorded. First, regarding the cross section including the achromatic axis of the color system at a predetermined hue angle, the coordinate axis indicating brightness is L, the coordinate axis indicating saturation is C, and any coordinates on the CL plane are set by the setting process. Set to (l, c). Then, by the change processing, the point corresponding to the color image information outside the color reproduction area of the output system is changed to l = ac + b (a is an inclination, b is an intersection with the L axis of the achromatic color) in the achromatic direction of the output color system. ), The value of a or b is changed according to the predetermined hue angle.
[0017]
The invention according to claim 8 is the recording medium according to claim 7, wherein on the hue surface, the two basics of the predetermined hue angle and both sides of the color corresponding to the predetermined hue angle are provided. A program for causing the computer to further execute the process of changing the value of a or b based on the difference from the hue angle of the color is recorded.
[0018]
Furthermore, the invention according to claim 9 is the recording medium according to claim 7, wherein the predetermined hue angle is θi, and hue angles of two basic colors on both sides of the color corresponding to the predetermined hue angle. Are θr and θy (θr <θi <θy), and the values of the coefficients a and b at the hue angles θr and θy are ar, br, ay, and by, respectively, the values of the coefficients a and b at the hue angle θi are
a = (ar × (θy−θi) + ay × (θi−θr)) / (θy−θr)
b = (br × (θy−θi) + by × (θi−θr)) / (θy−θr)
A program for causing the computer to further execute the processing calculated by the above is recorded.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the following, preferred embodiments of the present invention will be described with reference to the drawings.
[0020]
1 is a block diagram illustrating an image processing system that performs color conversion processing according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a specific hardware configuration example.
[0021]
In the embodiment described below, the color CRT gradation color specification data as the input color image information 10 is input to the image processing device 20, and the image processing device 20 performs predetermined image processing to output color image information. Assume that binary data for a printer is generated. The image processing apparatus 20 corresponds to a computer system including a computer 21, a hard disk 22, a media reading device 23, and the like.
[0022]
A program for executing the color conversion process according to the present invention is normally recorded and distributed on a recording medium DK such as a floppy disk or a CD-ROM in a form readable by the computer 21. The program is read by the media reader 23 and installed in the hard disk 22. The CPU is configured to read out a desired program from the hard disk 22 as appropriate and execute a desired process.
[0023]
Note that tone color data for color CRT is RGB (red, green, blue) tone data, and printer tone color data is CMY (cyan, magenta, yellow) binary data. The computer 21 as the image processing apparatus 20 converts RGB gradation data into CMY binary data.
[0024]
The embodiment is merely an example, and a color image is captured by the scanner 11 or the digital still camera 12 and the gradation colorimetric data is input to the image processing device 20. The present invention is also applied to the case where data for the CRT display 32 is generated. Here, the gradation data of RGB is used for each of the scanner 11, the digital still camera 12, and the display 32, but the scanner 11 or the digital still camera 12 and the display 32 usually have different color characteristics. is there. Therefore, in such a case, the computer 21 performs processing for converting RGB gradation data into other RGB gradation data.
[0025]
FIG. 3 is a diagram for explaining the functions of the computer 21. As shown in FIG. 3, the print data generated by the application 21a is input to the printer driver 21b, and the printer driver 21b converts the input print data into image data in a format requested by the printer 31. Convert. This conversion corresponds to the above-described processing for converting RGB gradation data into CMY binary data.
[0026]
The printer driver 21b refers to a rasterizer 21b1 that cuts out the scan range of the print head in the printer 31 from image data generated by the application 21a in units of screens, and RGB tone data with reference to a color conversion table for each pixel in the scan range. Is converted to CMY gradation data, and a gradation conversion section 21b3 is provided that converts the CMY gradation data into binary data. In this configuration, the color conversion unit 21b corresponds to a setting unit and a changing unit. Further, the display image data generated by the application 21a is written in a predetermined image memory by the video driver 21C and displayed on the display 32 via the hardware circuit.
[0027]
On the display 32, the color image is displayed with gradations in three primary colors (R, G, B) of red, green, and blue for each pixel arranged vertically and horizontally. In a general color printing apparatus, three colors of cyan, magenta, and yellow are displayed. The color (C, M, Y) or four colors (C, M, Y, K) with black added thereto is printed without gradation display. Therefore, for color printing, from the color conversion work from the display of the three primary colors (R, G, B) of red, green and blue to the display of three colors (C, M, Y) of cyan, magenta, and yellow, and from the gradation display. Work of gradation conversion to display without gradation is required.
[0028]
Color Conversion Processing by Color Conversion Unit 21b2 Next, color conversion processing by the color conversion unit 21b2 will be described with reference to FIG.
[0029]
The color conversion unit 21b2 first obtains the correspondence between the RGB color space and the CMY color space (step 42).
[0030]
Specifically, the color conversion unit 21b2 includes a color conversion table, and grid points in the conversion source color space in order to convert gradation color data between different color spaces by the color conversion table. Are associated with the gradation color data in the color space of the conversion destination. That is, the color conversion table is a three-dimensional lookup table for reading out CMY gradation data as coordinate values based on RGB gradation data. Then, the color conversion unit 21b2 refers to the lookup table and obtains a correspondence relationship between the color of a certain coordinate in the (R, G, B) color space and the (C, M, Y) color space. .
[0031]
That is, the color conversion unit 21b2 determines the coordinates in the (C, M, Y) color space corresponding to the color of a certain coordinate in the (R, G, B) color space in Step 42 (hereinafter, “target point P”). Called).
[0032]
Here, if at least the conversion source (R, G, B) display has 256 gradations for each color, the color conversion table of about 16.7 million (256 × 256 × 256) elements must be held. Don't be. However, in order to efficiently use the storage resource, a correspondence relationship is not prepared for all coordinate values, but a correspondence relationship is prepared for lattice points at a predetermined interval, and an interpolation operation is used together. That is, when the correspondence of the (C, M, Y) color space is obtained for the color of a certain coordinate in the (R, G, B) color space, the correspondence of the grid points surrounding the certain coordinate is used. Then, the correspondence relationship of the certain coordinates is obtained through operations such as linear interpolation.
[0033]
Next, the color conversion unit 21b2 determines whether or not the target point P exists outside the color reproduction region of the output color system (the printer 31 in the present embodiment) (step 44).
[0034]
When the target point P exists outside the color reproduction region of the output color system (step 44, Yes), the color conversion unit 21b2 calculates a substitute target point Q to be converted instead of the target point P. Compression processing is performed (step 46). Details of the color compression processing will be described later. The reason why the target point P exists outside the color reproduction area of the output color system is that the color reproduction area of the output system is narrower than the color reproduction area of the input system.
[0035]
Finally, when the target point P exists outside the color reproduction region of the output color system (step 44, Yes), the color conversion unit 21b2 performs color compression processing (step 46), and then substitute target points. RGB gradation data is converted into CMY gradation data based on Q (step 48), and if the target point P exists in the color reproduction region of the output color system (step 44, No), color compression processing is performed. Instead, the RGB gradation data is converted into CMY gradation data based on the target point P (step 48).
[0036]
Color Compression Processing Hereinafter, the color compression processing (step 46) in FIG. 4 will be described in detail.
[0037]
FIG. 5 shows a diagram for explaining the color compression processing according to the present invention, and FIG. 6 shows a cut surface when the L * a * b * space is cut by a plane including the L axis at the hue angle θi. FIG. 7 is a flowchart for explaining the color compression processing according to the present invention.
[0038]
In this embodiment, color conversion is performed by changing a function for performing color compression processing according to the hue angle. That is, according to the present embodiment, color conversion is performed in consideration of a change in the color reproduction region due to a change in hue angle, thereby enabling more faithful color reproduction.
[0039]
FIG. 5 shows hue angles of R (red), Y (yellow), G (green), C (cyan), B (blue), and M (magenta) on the a ^* b ^* plane. That is, in FIG. 5, the hue angle of R (red) is θr, the hue angle of Y (yellow) is θy, the hue angle of G (green) is θg, the hue angle of C (cyan) is θc, and B (blue) Is set to θb, and the hue angle of M (magenta) is set to θm. The coefficients La and α of the function for performing the color compression processing at each hue angle are Lr, αr; Ly, αy; Lg, αg; Lc, αc; Lb, αb; Lm, αm, respectively.
[0040]
As shown in FIG. 6, in this embodiment, it is assumed that the color reproduction area of the display 32 is wider than the color reproduction area of the printer 31. In this embodiment, target points P (ai, bi, Lp) that are included in the color reproduction area of the display 32 but are not included in the color reproduction area of the printer 31 are included in the color reproduction area of the printer 31. Is converted to an alternative target point Q. Here, the hue angle θi is
θi ＝ arctan (bi / ai)
As required.
[0041]
As will be described below, these conversion processes are performed in different ways for the high brightness area (L ≧ La) and the low brightness area (L <La).
[0042]
Point Q1 corresponds to the color when point P1 is linearly compressed to the printer's color reproduction area boundary with point P1 pointing to point La, and point Q2 is the color of the printer with point P2 pointing to point La This is a point corresponding to a color when linearly compressed to the reproduction area boundary surface.
[0043]
On the other hand, the point L ′ (0, L ′) is a point on the L axis indicating the direction of color compression in the low lightness region (L <La). Point Q3 corresponds to the color when point P3 is linearly compressed to the color reproduction area boundary surface of the printer toward point L ', and point Q4 is the printer corresponding to point P4 toward point L'. This is a point corresponding to the color when the color reproduction region boundary surface is linearly compressed.
[0044]
Next, with reference to FIG. 7, a color compression process according to this embodiment for compressing the target point P to the alternative target point Q will be described. The following processing is executed by the CPU in the computer 21 constituting the color conversion unit 21b2.
[0045]
As shown in FIG. 5, the a ^* b ^* plane is divided into six regions by six hue angles θr, θy, θg, θc, θb, and θm. In this embodiment, in order to simplify the description, a case where θi exists in a region sandwiched between R and Y (θr <θi <θy) will be described.
[0046]
First, the CPU
Lai ＝ (Lar × (θy−θi) + Lay × (θi−θr)) / (θy−θr) (1)
Is calculated (step 70), and it is determined whether or not the L coordinate value Lp of the target point P (ai, bi, Lp) to be compressed is less than Lai (step 72). That is, it is determined whether the target point exists in the low lightness area (Lp <Lai) or in the high lightness area (Lp ≧ Lai), and the low lightness area and the high lightness area are subjected to different processing, and more Enables color reproduction with high fidelity.
[0047]
Next, the CPU, when the L coordinate value Lp of the target point P (ai, bi, Lp) to be compressed is less than Lai, that is, when the target point exists in the low brightness area (step 72, Yes),
αi = (αr × (θy−θi) + αy × (θi−θr)) / (θy−θr) (2)
Is calculated (step 74),
L '＝ Lai− (Lai−Lp) × αi (3)
To the point L ′ (0, 0, L ′), the image is compressed to the color reproduction area boundary surface of the printer (step 76), and the process is terminated.
[0048]
From (3)
L'−Lp = (1−αi) (Lai−Lp) (4)
And also
0 ≦ αr, αy ≦ 1, Lai <Lp
given that,
As is clear from FIG.
(θy−θi)> 0, (θi−θr)> 0, and (θy−θr)> 0
(4) is
L'−Lp = (1−αi) (Lai−Lp) ≧ 0 (5)
It becomes. So always
L '≧ Lp
Therefore, the brightness value of the target point P is compressed in a direction that does not decrease. In the low lightness area, the difference in color reproduction range between the display and the printer is small, so it is preferable to preserve the lightness.
[0049]
Therefore, by performing the color compression process in this way, in the low lightness region, although the lightness is slightly reduced, the lightness is preferentially stored, so that a low lightness color can be reproduced more faithfully.
[0050]
On the other hand, when the L coordinate value Lp of the target point P (ai, bi, Lp) to be compressed is greater than or equal to Lai, that is, when the target point exists in the high brightness area (No in step 72), the point P is converted to the point Lai. (Step 78), and the process ends. Since the display has a color with high saturation in a high lightness region as compared with a printer, the saturation of the high lightness color is extremely compressed when importance is attached to preservation of lightness.
[0051]
Therefore, by performing the color compression processing in this way, the high brightness region reduces the lightness but preserves the saturation more preferentially, so the color difference is reduced and the bright and highly saturated color is more faithfully preserved. Can be reproduced.
[0052]
In the present embodiment, only the case where θi exists in the region sandwiched between R and Y has been described, but the compression processing can be similarly performed for the other five regions. Further, the present invention can be applied regardless of whether the hue angles θr, θy, θg, θc, θb, and θm are hue angles of a display or a printer. Furthermore, the values of αr, αy, αg, αc, αb, and αm are adjusted by actually converting and outputting the colors of each hue.
[0053]
It is desirable to change these values for each hue. That is, these coefficients depend on the shape of the color reproduction region in each hue. For example, in order to reproduce B (blue) of the display with a printer, it is preferable to reproduce the brightness higher. On the other hand, in order to reproduce G (green) of the display, it is preferable to lower the brightness and increase the saturation as much as possible.
[0054]
According to this embodiment, in a region sandwiched between two basic colors, the difference between the hue angle θi of the target point P to be compressed and the hue angles of the two basic colors is obtained, and the equations (1), ( Since the weighted average is taken as in 2), more faithful color reproduction is possible in consideration of the hue. Taking the weighted average in this way is most effective in performing faithful color reproduction in the case of the linear expressions such as (1) and (2).
[0055]
【The invention's effect】
According to the color conversion method according to claim 1, the color conversion device according to claim 8, and the processing of the program recorded in the recording medium according to claim 12, it is outside the color reproduction region of the output system. When the point corresponding to the color image information is compressed in the achromatic direction of the output color system using l = ac + b (a is the inclination, and b is the intersection with the achromatic L axis), the predetermined hue angle Since the value of a or b is changed according to the color change, the color conversion is performed in consideration of the change of the color reproduction region due to the change of the hue angle, thereby enabling more faithful color reproduction.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image processing system that performs color conversion processing according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a specific hardware configuration example of the image processing system.
FIG. 3 is a diagram for explaining functions of a computer 21;
FIG. 4 is a flowchart for explaining color conversion processing by a color conversion unit 21b;
FIG. 5 is a diagram for explaining the concept of color compression processing according to the present invention;
FIG. 6 is a plane including the L axis at the hue angle θi and a cut surface when the L * a * b * space is cut.
FIG. 7 is a flowchart for explaining color compression processing according to the present invention;
[Explanation of symbols]
11 Scanner 12 Digital Still Camera 20 Image Processing Device 21 Computer 21a Application 21b Printer Driver 21b1 Rasterizer 21b2 Color Conversion Unit 21b3 Tone Conversion Unit 21c Video Driver 22 Hard Disk 23 Media Reading Device 31 Printer 32 Display

Claims (3)

When the color reproduction area of the output system is narrower than the color reproduction area of the input system, color conversion is performed when color image information within the color reproduction area of the input system and outside the color reproduction area of the output system is input A method,
For a cross section including the achromatic axis of the color system at a predetermined hue angle, the coordinate axis indicating lightness is set to L, the coordinate axis indicating chroma is set to C, and arbitrary coordinates on the CL plane are set to (l, c). A setting process;
When the point corresponding to the color image information outside the color reproduction area of the output system is linearly compressed toward the one point on the L axis of the achromatic color in the achromatic color direction of the output color system, the predetermined hue angle is set to the predetermined hue angle. A changing step of changing the coordinates of the one point in response,
With
The predetermined hue angle is θi, the hue angles of two basic colors on both sides of the color corresponding to the predetermined hue angle are θr and θy (θr <θi <θy), and the one point at the hue angles θr and θy is A color conversion method in which the coordinates of one point at the hue angle θi are calculated by (Lr × (θy−θi) + Ly × (θi−θr)) / (θy−θr) where the coordinates are Lr and Ly, respectively. When the color reproduction area of the output system is narrower than the color reproduction area of the input system, color conversion is performed when color image information within the color reproduction area of the input system and outside the color reproduction area of the output system is input A device,
For a cross section including the achromatic axis of the color system at a predetermined hue angle, the coordinate axis indicating lightness is set to L, the coordinate axis indicating chroma is set to C, and arbitrary coordinates on the CL plane are set to (l, c). Setting means;
When the point corresponding to the color image information outside the color reproduction area of the output system is linearly compressed toward the one point on the L axis of the achromatic color in the achromatic color direction of the output color system, the predetermined hue angle is set to the predetermined hue angle. A changing means for changing the coordinates of the one point in response,
With
The predetermined hue angle is θi, the hue angles of two basic colors on both sides of the color corresponding to the predetermined hue angle are θr and θy (θr <θi <θy), and the one point at the hue angles θr and θy is A color conversion apparatus that calculates the coordinates of the one point at the hue angle θi by (Lr × (θy−θi) + Ly × (θi−θr)) / (θy−θr), where the coordinates are Lr and Ly, respectively. When the color reproduction area of the output system is narrower than the color reproduction area of the input system, color conversion is performed when color image information within the color reproduction area of the input system and outside the color reproduction area of the output system is input A computer-readable recording medium storing a program for causing a computer to execute processing,
For a cross section including the achromatic axis of the color system at a predetermined hue angle, the coordinate axis indicating lightness is set to L, the coordinate axis indicating chroma is set to C, and arbitrary coordinates on the CL plane are set to (l, c). Configuration process,
When the point corresponding to the color image information outside the color reproduction area of the output system is linearly compressed toward the one point on the L axis of the achromatic color in the achromatic color direction of the output color system, the predetermined hue angle is set to the predetermined hue angle. A change process for changing the coordinates of the one point in response,
Is a computer-readable recording medium recording a program for causing a computer to execute
The predetermined hue angle is θi, the hue angles of two basic colors on both sides of the color corresponding to the predetermined hue angle are θr and θy (θr <θi <θy), and the one point at the hue angles θr and θy is When the coordinates are Lr and Ly, respectively, the computer further calculates the coordinates of the one point at the hue angle θi by (Lr × (θy−θi) + Ly × (θi−θr)) / (θy−θr) A recording medium on which a program for recording is recorded.

Images