JP5939132B2 - Image processing apparatus and image processing program - Google Patents

Description

  The present invention relates to an image processing apparatus and an image processing program.

  In Patent Document 1, the mapping method for mapping all of the input color gamuts to the output color gamut will map even the color gamuts that are not actually used to the output color gamut, resulting in lower saturation than necessary. The input gamut data corresponding to the input device is acquired and set, and then the used gamut data corresponding to the input device is acquired and set, and then Obtain and set the output color gamut data corresponding to the output device, then map the input image to the use color gamut based on the set input color gamut data and the use color gamut data, and then set the use It is disclosed that an image mapped to a use color gamut is mapped to an output color gamut based on the color gamut data and the output color gamut data.

  In Patent Document 2, when color data is converted between color gamuts having different sizes, color loss, brightness variation of the entire image, and gradation collapse are prevented, and the appearance of the display image and the printed image as a whole is disclosed. In the virtual gamut derivation process, the brightness, saturation, and / or hue angle of the second gamut is converted, and the extended virtual gamut including all the brightness of the first gamut In the color data changing process, the brightness, saturation, and hue angle are changed for color data that is not included in the virtual color gamut among the color data in the first color gamut, and the color data included in the virtual color gamut. The third color data is derived, and the color data generation process performs a conversion on the third color data that is the reverse of the conversion performed on the second color gamut in the virtual color gamut derivation process. Is disclosed.

JP 2006-254369 A JP 2000-165692 A

  According to the present invention, when there is an area where the second color gamut can express a higher brightness than the first color gamut, the gradation characteristics in the first image signal cannot be maintained in the second image signal. An object of the present invention is to provide an image processing apparatus and an image processing program that can prevent this.

The gist of the present invention for achieving the object lies in the inventions of the following items.
According to the first aspect of the present invention, a first conversion unit that converts a first image signal handled by the first image device into an image signal of a predetermined color space, and a first image device that can be expressed by the first image device. Based on the first color gamut information indicating the first color gamut and the second color gamut information indicating the second color gamut that can be expressed by the second image device, the conversion processing is performed by the first conversion unit. Correction means for correcting the image signal, mapping means for mapping the image signal corrected by the correction means into the second color gamut, and image signal processed by the mapping means for the second image device The second conversion means for converting into a second image signal handled by the correction means, wherein the correction means extracts a point where the first color gamut and the second color gamut intersect, and the intersection point Between the first color gamut and the second color gamut in a lighter area than Based on the distance, than the second color gamut to generate a control point on a side brightness is high, an image processing apparatus characterized by correcting the image signal so as to pass through the control points.

  According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the second image device represents an image with a basic color and a color material of a color other than the basic color. is there.

  According to a third aspect of the present invention, the correction means is a region having a lightness higher than the maximum saturation point of the first color gamut or the second color gamut, and the second color at the same saturation. When there is a region where the lightness of the gamut is higher than the lightness of the first color gamut, or when there is a region where the saturation of the second color gamut is higher than the saturation of the first color gamut at the same lightness The image processing apparatus according to claim 1, wherein the correction is performed.

According to a fourth aspect of the present invention, the correcting means extracts a point where the first color gamut and the second color gamut intersect, and a color gamut based on the basic color in a region having a higher brightness than the intersecting point. And a control point is generated on the side having higher brightness than the second color gamut based on the distance between the second color gamut and the image signal is corrected so as to pass through the control point. An image processing apparatus according to claim 2 or claim 3 dependent on claim 2 .

The invention according to claim 5 is a first conversion means for converting the first image signal handled by the first image device into an image signal of a predetermined color space, and a first image device that can be expressed by the first image device. Based on the first color gamut information indicating the first color gamut and the second color gamut information indicating the second color gamut that can be expressed by the second image device, the conversion processing is performed by the first conversion unit. Correction means for correcting the image signal, mapping means for mapping the image signal corrected by the correction means into the second color gamut, and image signal processed by the mapping means for the second image device Comprising a second conversion means for converting into a second image signal handled by the second image device, wherein the second image device represents an image with a basic color and a color material of a color other than the basic color, The correcting means intersects the first color gamut and the second color gamut. A side where lightness is higher than that of the second color gamut based on the distance between the color gamut of the basic color and the second color gamut in a region where lightness is higher than that of the intersecting point. An image processing apparatus is characterized in that a control point is generated and an image signal is corrected so as to pass through the control point .
According to a sixth aspect of the present invention, the correction means is a region having a lightness higher than a point of maximum saturation of the first color gamut or the second color gamut, and the second color at the same saturation. When there is a region where the lightness of the gamut is higher than the lightness of the first color gamut, or when there is a region where the saturation of the second color gamut is higher than the saturation of the first color gamut at the same lightness The image processing apparatus according to claim 5, wherein the correction is performed.
According to a seventh aspect of the present invention, the correction means extracts a point where the first color gamut and the second color gamut intersect, and the first color gamut in a region having a higher brightness than the intersecting point. And a control point is generated on the side having higher brightness than the second color gamut based on the distance between the second color gamut and the image signal is corrected so as to pass through the control point. An image processing apparatus according to claim 5 or 6.

The invention according to claim 8 is the image processing apparatus according to any one of claims 1 to 7 , wherein the correction unit corrects the second image signal.

The invention according to claim 9 is the image processing apparatus according to any one of claims 1 to 8 , wherein the correction unit generates a color conversion correction coefficient.

According to a tenth aspect of the present invention, the first image device expresses the first conversion means for converting the first image signal handled by the first image device into an image signal of a predetermined color space. Conversion by the first conversion means based on the first color gamut information indicating the first color gamut that can be performed and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the processed image signal; mapping means for mapping the image signal corrected by the correction means into the second color gamut; and image signal processed by the mapping means for the second image signal. Functioning as second conversion means for converting into a second image signal handled by the image equipment, and the correction means extracts a point where the first color gamut and the second color gamut intersect, The first in a region that is lighter than the intersecting point A control point is generated on the side having higher brightness than the second color gamut based on the distance between the color gamut and the second color gamut, and the image signal is corrected so as to pass through the control point. This is a featured image processing program.
According to the eleventh aspect of the present invention, the first image device expresses the computer by means of first conversion means for converting the first image signal handled by the first image device into an image signal of a predetermined color space. Conversion by the first conversion means based on the first color gamut information indicating the first color gamut that can be performed and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the processed image signal; mapping means for mapping the image signal corrected by the correction means into the second color gamut; and image signal processed by the mapping means for the second image signal. The second image device functions as a second conversion means for converting into a second image signal handled by the image device, and the second image device expresses an image with a basic color and a color material of a color other than the basic color. And the correction means includes the first color gamut. A point where the second color gamut intersects is extracted, and the second color gamut is extracted based on a distance between the color gamut based on the basic color and the second color gamut in a region having a higher brightness than the intersecting point. An image processing program is characterized in that a control point is generated on the side where brightness is higher than a color gamut, and an image signal is corrected so as to pass through the control point.

According to the image processing apparatus of the first aspect, when there is a region in which the second color gamut can express higher brightness than the first color gamut, the gradation characteristic in the first image signal is the second. It is possible to prevent the image signal from becoming unsustainable. In addition, the image signal can be corrected so that the brightness and the saturation are higher than those in the second color gamut.

  According to the image processing apparatus of the second aspect, when the second image device represents an image with a basic color and a color material other than the basic color, the gradation characteristics in the first image signal are It can be prevented that the second image signal cannot be maintained.

  According to the image processing apparatus of the third aspect, even when correction is not necessary, it is possible to prevent image quality deterioration such as saturation reduction by performing correction.

According to the image processing apparatus of the fourth aspect, it is possible to correct the image signal so that the brightness is higher than that of the second color gamut.

According to the image processing apparatus of the fifth aspect, when there is a region in which the second color gamut can express higher brightness than the first color gamut, the gradation characteristic in the first image signal is the second. It is possible to prevent the image signal from becoming unsustainable. Further, when the second image device expresses an image with a basic color and a color material other than the basic color, the gradation characteristics in the first image signal cannot be maintained with the second image signal. This can be prevented. In addition, the image signal can be corrected so that the brightness is higher than that of the second color gamut.
According to the image processing apparatus of the sixth aspect, it is possible to prevent image quality deterioration such as saturation reduction by performing correction even when correction is not necessary.
According to the image processing device of the seventh aspect, it is possible to correct the image signal so that the brightness and the saturation are higher than those of the second color gamut.

According to the image processing device of the eighth aspect , by correcting the second image signal, it is possible to prevent the gradation characteristics in the first image signal from being maintained by the second image signal.

According to the image processing apparatus of the ninth aspect , the color conversion correction coefficient can be generated.

According to the image processing program of the tenth aspect , when there is a region where the second color gamut can express a higher brightness than the first color gamut, the gradation characteristic in the first image signal is the second. It is possible to prevent the image signal from becoming unsustainable. In addition, the image signal can be corrected so that the brightness and the saturation are higher than those in the second color gamut.
According to the image processing program of claim 11, when there is a region where the second color gamut can express a higher brightness than the first color gamut, the gradation characteristics in the first image signal are the second. It is possible to prevent the image signal from becoming unsustainable. Further, when the second image device expresses an image with a basic color and a color material other than the basic color, the gradation characteristics in the first image signal cannot be maintained with the second image signal. This can be prevented. In addition, the image signal can be corrected so that the brightness is higher than that of the second color gamut.

It is a conceptual module block diagram about the structural example of 1st Embodiment. It is explanatory drawing which compares the output color gamut example by a basic color, and the input color gamut example. It is explanatory drawing which compares the example of an output color gamut when a special color is added to the basic color, and the example of an input color gamut. It is explanatory drawing which compares the example of an output color gamut when a special color is added to the basic color, and the example of an input color gamut. It is a flowchart which shows the process example by 1st Embodiment. It is a flowchart which shows the process example by 1st Embodiment. It is explanatory drawing which shows the process example by 1st Embodiment. It is explanatory drawing which shows the process example by 1st Embodiment. It is explanatory drawing which shows the process example by a prior art. It is explanatory drawing which shows the process example by 1st Embodiment. It is a conceptual module block diagram about the structural example of 2nd Embodiment. It is explanatory drawing which shows the process example by 2nd Embodiment. It is explanatory drawing which shows the process example by 2nd Embodiment. It is explanatory drawing which shows the process example by 2nd Embodiment. It is explanatory drawing which shows the process example by 3rd Embodiment. It is a block diagram which shows the hardware structural example of the computer which implement | achieves this Embodiment.

First, before explaining the present embodiment, an image processing technique as a premise thereof will be explained. This description is intended to facilitate understanding of the present embodiment.
This will be described with reference to FIGS. There is a technique related to color conversion that uses an input / output color gamut when converting an input image signal to an output image signal. For example, the input color gamut is a color gamut that can be expressed by a display that is an input device, and the output color gamut is a color gamut that can be expressed by a printer that is an output device. In such a case, in general, the relationship between the input color gamut and the output color gamut is that the input color gamut 210 is wider than the output color gamut 220, as shown in the example of FIG. Therefore, converting the input image signal to the output image signal is a process of moving the input image signal 212 to the output image signal 222 as shown in FIG. This graph shows the relationship between lightness and saturation at a certain hue angle, where the vertical axis is lightness and the horizontal axis is saturation, indicating that it is brighter at the top and brighter at the right. ing.
As an output device having the output color gamut 220 shown in FIG. 2, for example, color materials of four colors (C (Cyan), M (Magenta), Y (Yellow), K (breakK)), which are called basic colors, are used. Used.

  However, the output device is a special color (for example, R (Red), G (Green), B (Blue), O (Orange), V (Violet), etc.) or a combination of these four basic colors ), The output color gamut 330 is wider than the basic color gamut 320 as shown in the example of FIG. There are areas that become wider, but there are still areas that are narrower than the input color gamut 310. Then, when the input image signal is converted into the output image signal, the input image signal 312 is moved to the right as shown in the output image signal 332 and the left image is moved as shown in the example of FIG. Processing is required. The special color means a color material having a color different from the basic four colors.

The example of FIG. 4A shows the relationship between the input color gamut 410a and the output color gamut 430a at a certain hue angle. Although the output color gamut 430a is wider than the basic color gamut 420a, it is on the higher lightness side (shown in the figure) than the maximum saturation point of the input color gamut 410a or the output color gamut 430a (the vertex of the input color gamut 410a or the output color gamut 430a in the figure). In the upper area, the input color gamut 410a and the output color gamut 430a intersect at a point where the output color gamut 430a is wider than the input color gamut 410a and the input color gamut 410a is wider than the output color gamut 430a. Divided into regions 450a. Therefore, conversion that moves to the right is necessary in the region 440a, and conversion that moves to the left is necessary in the region 450a.
The example of FIG. 4B shows the relationship between the input color gamut 410b and the output color gamut 430b at different hue angles. Although the positions where the input color gamut 410b and the output color gamut 430b intersect are different, regions 440b and 450b that require the same processing as in FIG. 4A are generated.
It should be noted that such a phenomenon does not necessarily occur when a special color is added to the four basic colors, and does not necessarily occur at all hue angles. Even if a spot color is added, the input color gamut may still be wider than the output color gamut as a whole, or the input color gamut may be wider than the output color gamut depending on the hue angle. For example, when orange is added as a special color, the phenomenon as shown in the region 440a in the example of FIG. 4A occurs in the hue angles mainly indicating yellow and magenta, but not in other hue angles. There is.

Hereinafter, examples of various preferred embodiments for realizing the present invention will be described with reference to the drawings.
FIG. 1 shows a conceptual module configuration diagram of a configuration example of the present embodiment.
The module generally refers to components such as software (computer program) and hardware that can be logically separated. Therefore, the module in the present embodiment indicates not only a module in a computer program but also a module in a hardware configuration. Therefore, the present embodiment is a computer program for causing these modules to function (a program for causing a computer to execute each procedure, a program for causing a computer to function as each means, and a function for each computer. This also serves as an explanation of the program and system and method for realizing the above. However, for the sake of explanation, the words “store”, “store”, and equivalents thereof are used. However, when the embodiment is a computer program, these words are stored in a storage device or stored in memory. This means that the device is controlled so as to be stored. Modules may correspond to functions one-to-one, but in mounting, one module may be configured by one program, or a plurality of modules may be configured by one program, and conversely, one module May be composed of a plurality of programs. The plurality of modules may be executed by one computer, or one module may be executed by a plurality of computers in a distributed or parallel environment. Note that one module may include other modules. Hereinafter, “connection” is used not only for physical connection but also for logical connection (data exchange, instruction, reference relationship between data, etc.). “Predetermined” means that the process is determined before the target process, and not only before the process according to this embodiment starts but also after the process according to this embodiment starts. In addition, if it is before the target processing, it is used in accordance with the situation / state at that time or with the intention to be decided according to the situation / state up to that point. When there are a plurality of “predetermined values”, they may be different values, or two or more values (of course, including all values) may be the same. In addition, the description having the meaning of “do B when it is A” is used in the meaning of “determine whether or not it is A and do B when it is judged as A”. However, the case where it is not necessary to determine whether or not A is excluded.
In addition, the system or device is configured by connecting a plurality of computers, hardware, devices, and the like by communication means such as a network (including one-to-one correspondence communication connection), etc., and one computer, hardware, device. The case where it implement | achieves by etc. is included. “Apparatus” and “system” are used as synonymous terms. Of course, the “system” does not include a social “mechanism” (social system) that is an artificial arrangement.
In addition, when performing a plurality of processes in each module or in each module, the target information is read from the storage device for each process, and the processing result is written to the storage device after performing the processing. is there. Therefore, description of reading from the storage device before processing and writing to the storage device after processing may be omitted. Here, the storage device may include a hard disk, a RAM (Random Access Memory), an external storage medium, a storage device via a communication line, a register in a CPU (Central Processing Unit), and the like.

The image processing apparatus according to the present embodiment performs color gamut mapping processing. As shown in the example of FIG. 1, the input color space conversion module 110, the input image signal correction module 120, and the color gamut information storage module are used. 130, a mapping module 140, and an output color space conversion module 150. The color gamut mapping process refers to a case where a color gamut that can be expressed by one image device is different from a color gamut that can be expressed by the other image device among a plurality of image devices. To map to. A color gamut forms an outline of an image signal handled by any of the image devices. Specifically, the input color gamut forms the outline of the input image signal, and the output color gamut forms the outline of the output image signal. The image signal is converted by the above mapping. Therefore, converting the color gamut (including correction and the like) is synonymous with converting the image signal. The description that the color gamuts intersect indicates that the outline of the input color gamut (the line surrounding the color gamut) and the outline of the output color gamut intersect.
The term “input” is used as a term relating to data received by an image processing apparatus or a part thereof, a process for inputting data, a device related to an input process, an input / output channel, or a state related to them for storage or processing. .

The input color space conversion module 110 is connected to the input image signal correction module 120. The input color space conversion module 110 converts the first image signal handled by the first image device into an image signal in a predetermined color space. For example, a display or the like corresponds to the first image device. For example, an RGB image signal corresponds to the first image signal. As the predetermined color space, for example, a La ^* b ^* color space that does not depend on a specific image device is applicable. The conversion by the input color space conversion module 110 is a color space conversion, for example, conversion from RGB image information to La ^* b ^* image information, and this conversion processing may be performed using a known technique. . Of course, not only La ^* b ^* but also other color spaces such as XYZ may be used. When the input image signal is La ^* b ^* , the input color space conversion module 110 is not necessary, and the input image signal La ^* b ^* is input to the input image signal correction module 120.

The input image signal correction module 120 is connected to the input color space conversion module 110, the color gamut information storage module 130, and the mapping module 140. The input image signal correction module 120 includes first color gamut information (input color gamut information 132) indicating a first color gamut that can be expressed by the first image device, and second information that can be expressed by the second image device. The image signal converted by the input color space conversion module 110 is corrected based on the second color gamut information (output color gamut information 134) indicating the color gamut.
The input image signal correction module 120 is a region having a lightness higher than the maximum saturation point of the first color gamut or the second color gamut, and the lightness of the second color gamut is the same in the same saturation. Correction may be performed when there is an area higher than the brightness of the first color gamut or when there is an area where the saturation of the second color gamut is higher than the saturation of the first color gamut at the same brightness. Good. If it demonstrates using the example of Fig.4 (a), the area | region where the output color gamut 430a is higher than the input color gamut 410a should just exist above the vertex of the input color gamut 410a or the output color gamut 430a. The output color gamut 430a may have a higher brightness than the input color gamut 410a as a whole, or the output color gamut 430a may have a higher brightness than the input color gamut 410a in some areas. Therefore, the output color gamut 430a may include a region having the same brightness as the input color gamut 410a or a region having the same brightness.

  Then, the input image signal correction module 120 extracts a point where the first color gamut and the second color gamut intersect, and the first color gamut and the second color in a region where the brightness is higher than the intersecting point. Based on the distance between the areas, a control point is generated on the side where the brightness is higher than that of the second color gamut, and the image signal is corrected so as to pass through the control point. The region having a higher brightness than the intersecting point is also a region between the intersecting point and the point of maximum brightness in the first color gamut or the second color gamut. The distance is one of the brightness difference and the saturation difference between the first color gamut and the second color gamut, or a combination thereof. This correction process will be described in detail later with reference to FIG. In addition, the intersection is not extracted first, but controlled from the brightness of the maximum saturation point and a predetermined correction coefficient (for example, a position of 1/3 from white due to the brightness difference between the brightness of white and the maximum saturation). A point may be set and correction may be performed when the control point is on the higher brightness side (or higher saturation side) than the intersection.

  The color gamut information storage module 130 stores input color gamut information 132 and output color gamut information 134 and is connected to the input image signal correction module 120. The input color gamut information 132 is information indicating a color gamut that can be expressed by a display, for example. The output color gamut information 134 is information indicating a color gamut that can be expressed by a printer, for example. These are data obtained by measuring in advance the color gamut that can be expressed by the first image device and the second image device. The second image device may represent an image with a basic color and a color material of a color other than the basic color. For example, the basic colors are the four basic colors (YMCK) described above, and the colors other than the basic colors are special colors.

The mapping module 140 is connected to the input image signal correction module 120 and the output color space conversion module 150. The mapping module 140 maps the image signal corrected by the input image signal correction module 120 into the second color gamut. This is a so-called mapping process, and a known technique may be used for this process. Note that when the mapping is holding the lightness, the movement is in the saturation direction, and when the mapping is holding the saturation, the movement is in the lightness direction.
The output color space conversion module 150 is connected to the mapping module 140. The output color space conversion module 150 converts the image signal mapped by the mapping module 140 into a second image signal (output image signal 195) handled by the second image device. For example, a printer or the like corresponds to the second image device. The conversion by the output color space conversion module 150 is a color space conversion, for example, conversion from La ^* b ^* image information to CMYK + spot color image information, and this conversion processing uses a known technique. That's fine. Then, the second image device processes the output image signal 195. Specifically, the printer performs printing.

FIG. 5 is a flowchart illustrating a processing example according to the first exemplary embodiment.
In step S502, the input color space conversion module 110 receives the input image signal 105.
In step S504, the input color space conversion module 110 converts the input image signal 105 into the La ^* b ^* color space.
In step S506, the input image signal correction module 120 corrects the image signal. This process will be described in detail using the example of FIG.
In step S508, the mapping module 140 converts the image signal.
In step S510, the output color space conversion module 150 converts the image signal into a basic color + spot color space.
In step S512, the output color space conversion module 150 outputs an image signal.

FIG. 6 is a flowchart illustrating a processing example (particularly, a processing example by the input image signal correction module 120) according to the first embodiment.
In step S602, the position information of the image signal is acquired. More specifically, the position in the color space of the image signal at a certain hue angle is calculated.
In step S604, it is determined whether or not correction is necessary. If necessary, the process proceeds to step S606. Otherwise, the process ends (step S699). Referring to the example of FIG. 7, the determination here is whether or not there is a region 740 in which the output color gamut 720 is wider than the input color gamut 710 in the region where the brightness is higher than the point 784 which is the maximum saturation. If it exists, it is determined that correction is necessary.

In step S606, input color gamut information 132 and output color gamut information 134 are acquired.
In step S608, the intersection of the color gamut is extracted and the starting point is set. This will be described with reference to the example of FIG. An intersection point 882 between the input color gamut 810 and the output color gamut 830 is extracted. Then, a point 892 at which the distance between the input color gamut 810 and the output color gamut 830 is maximum in the mapping direction is set as a starting point. For example, when the mapping direction is brightness maintenance, the point where the saturation difference is the maximum is the starting point. Even if the point 892 is not at the position shown in the figure, the input color gamut 810 is in a range narrower than the output color gamut 830 (between the point 880 and the intersection 882 on the output color gamut 830). Any point is acceptable.

In step S610, the distance between the starting point and the input color gamut is calculated. This will be described with reference to the example of FIG. A point 894 that is the intersection of a line segment having a predetermined angle and the input color gamut 810 is calculated through the starting point 892, and the distance between the point 892 and the point 894 is calculated.
In step S612, a control point is set using distance × coefficient. This will be described with reference to the example of FIG. A control point 886 is a point that passes through a point 894 that is the intersection of the starting point 892 and the input color gamut 810 and extends to the high brightness side. The coefficient is a predetermined number.
In step S614, the image signal is corrected using the control points. This will be described with reference to the example of FIG. A spline curve passing through the point 880, the control point 886, and the point 884 is generated, and the input color gamut 810 is corrected to generate a corrected input color gamut 850.

The example of FIG. 8 shows that the input color gamut 810 has been converted to the corrected input color gamut 850.
First, an intersection point 882 that is a point where the input color gamut 810 and the output color gamut 830 intersect is calculated. Note that the color gamut intersect means that the color gamut outlines intersect. Then, the distance between the input color gamut 810 and the output color gamut 830 at a predetermined position is calculated on the higher brightness side than the intersection 882 (region where the output color gamut 830 is wider than the input color gamut 810). As the predetermined position, for example, the point where the input color gamut 810 and the output color gamut 830 are farthest in the mapping direction, the center of the area, or 2/3 of the area closer to the white side (left side in the figure). There is a point in position. In the example of FIG. 8, the points 894 and 892 correspond. Therefore, the calculated distance is the distance between the point 894 and the point 892. In the above example, when the mapping direction is the lightness direction, the lightness difference (vertical direction in the figure) between the input color gamut 810 and the output color gamut 830 is the distance. When the mapping direction is the saturation direction, the saturation difference (horizontal direction in the figure) between the input color gamut 810 and the output color gamut 830 is the distance. When the mapping direction is an oblique direction, the square root of the value obtained by adding the square of the brightness difference and the square of the saturation difference between the input color gamut 810 and the output color gamut 830 is the distance.
Then, a point at a position away from the point 892 by a predetermined multiple (for example, twice) of the distance is set as a control point 886. A line passing through the point 880 (the point where the input color gamut 810 intersects the vertical axis, white), the control point 886, and the point 884 (the maximum saturation point of the input color gamut 810) is drawn to obtain the corrected input color gamut 850. Generate. The line passing through the point 880, the control point 886, and the point 884 may be, for example, a straight line, a spline curve, a curve obtained by inverting the original input color gamut 810, or the like.
By this correction processing, the input color gamut 810 is corrected to the input color gamut 850 after correction, and the input color gamut 850 after correction becomes a color gamut wider than the output color gamut 830.
When such correction is performed, the mapping by the mapping module 140 is a mapping from the corrected input color gamut 850 to the output color gamut 830.

FIG. 9 is an explanatory diagram showing an example of processing according to the prior art.
In the prior art, there were an image signal compressed with an image signal having the same hue angle (moved to the left in the example of FIG. 9) and an image signal expanded (moved to the right in the example of FIG. 9). The gradation reproducibility will be lost. Specifically, input image signals 912, 916, 924, and 928 having the same color are mapped to signals 914, 918, 922, and 926 after conventional mapping, respectively, and the input image signals 912 and 916 are respectively in the right direction. The image is expanded to the signals 914 and 918 after the conventional mapping, and the input image signals 924 and 928 are respectively compressed to the signals 922 and 926 after the conventional mapping in the left direction, and the image signals having the same hue angle are compressed and expanded. Are mixed.

FIG. 10 shows an example of mapping processing by the mapping module 140 for the corrected input color gamut 850 shown in the example of FIG.
In this embodiment, since the input color gamut 810 is corrected to the corrected input color gamut 850 and then the mapping is compressed, expansion and expansion are not mixed in the same hue, and only compression is performed. As a result, the gradation reproducibility is prevented from being lost. Specifically, the corrected input image signals 1014, 1018, 1024, and 1028 having the same hue are compressed into the mapped signals 1012, 1016, 1022, and 1026, respectively, and are not expanded.
In addition, since the control points are generated using the difference data between the input color gamut 810 and the output color gamut 830, the correction amount is only necessary, and the expansion amount to be corrected is suppressed. As a result, the amount of data inside the input color gamut 810 is suppressed.
Since the input color gamut 810 is changed, the image signal in the outline of the input color gamut 810 is converted into the outline of the output color gamut 830. Specifically, the corrected input image signal 1018 is compressed into a signal 1016 after mapping, and the corrected input image signal 1028 is compressed into a signal 1026 after mapping. As a result, the amount of dust is reduced and a wide color gamut is used.

A second embodiment will be described. As shown in the example of FIG. 11, the second embodiment has an input color space conversion module 110, an input image signal correction module 1120, a color gamut information storage module 1130, a mapping module 140, and an output color space conversion module 150. doing. In addition, the same code | symbol is attached | subjected to the site | part of the same kind as 1st Embodiment, and the overlapping description is abbreviate | omitted (hereinafter the same).
The input color space conversion module 110 is connected to the input image signal correction module 1120.

The input image signal correction module 1120 is connected to the input color space conversion module 110, the color gamut information storage module 1130, and the mapping module 140. The input image signal correction module 1120 is a process equivalent to the input image signal correction module 120 as in the first embodiment, that is, the first color indicating the first color gamut that can be expressed by the first image device. The image signal converted by the input color space conversion module 110 is corrected based on the gamut information and the second gamut information indicating the second gamut that can be expressed by the second image device. The input image signal correction module 1120 is an area having a lightness higher than the maximum saturation point of the first color gamut or the second color gamut, and the lightness of the second color gamut is the first color gamut. The correction may be performed when there is an area higher than the brightness of.
Then, the input image signal correction module 1120 extracts a point where the first color gamut and the second color gamut intersect, and the color gamut based on the basic color and the second color in the region having higher brightness than the intersecting point. Based on the distance between the areas, a control point is generated on the side where the brightness is higher than that of the second color gamut, and the image signal is corrected so as to pass through the control point. Specifically, using the input color gamut information 1132 and the output color gamut information A (spot color) 1134, a point where the first color gamut and the second color gamut intersect is extracted. Then, a distance is calculated using the output color gamut information B (basic color) 1136 and the output color gamut information A (spot color) 1134, and a control point is generated using the distance.

The color gamut information storage module 1130 stores input color gamut information 1132, output color gamut information A (spot color) 1134, and output color gamut information B (basic color) 1136, and is connected to the input image signal correction module 1120. Yes. The input color gamut information 1132 is information indicating a color gamut that can be expressed by a display, for example. The output color gamut information A (spot color) 1134 is information indicating a color gamut that a printer or the like can express using a combination of four basic colors and a spot color. The output color gamut information B (basic color) 1136 is information indicating a color gamut that the printer or the like can represent by using a combination of four basic colors (only four basic colors, not including a special color).
The mapping module 140 is connected to the input image signal correction module 1120 and the output color space conversion module 150.
The output color space conversion module 150 is connected to the mapping module 140.

FIG. 12 is an explanatory diagram showing a processing example (particularly a processing example by the input image signal correction module 1120) according to the second embodiment.
An intersection point 1282, which is a point where the input color gamut 1210 and the output color gamut 1230 intersect, is extracted, and between the basic four color gamuts 1220 and the output color gamut 1230 in a region (upper side in the drawing) having a lightness higher than the intersection point 1282. , A control point 1286 is generated on the side where the brightness is higher than the output color gamut 1230, and the input color gamut 1210 is corrected so as to pass through the control point. The corrected input color gamut 1250 is generated.
The distance between the point 1292 and the point 1294 is the distance between the color gamut 1220 of the basic four colors and the output color gamut 1230 which is a combination of the basic four colors and the spot color in the mapping direction (here, the saturation direction, the horizontal direction in the figure). The distance between the points (points 1292 and 1294) at which the saturation difference is maximized. Then, a point obtained by adding the distance to a point 1296 having the same brightness as the point 1292 of the input color gamut 1210 is set as a control point 1286. The point 1280 that is white, the control point 1286, and the point 1284 that is the maximum saturation point of the input color gamut 1210 are connected by a spline curve or the like, and the input color gamut 1210 is corrected to the corrected input color gamut 1250.

FIG. 13 is an explanatory diagram showing another processing example (particularly, a processing example by the input image signal correction module 1120) according to the second embodiment.
A control point a 1386 is calculated by a process equivalent to the example of FIG. In the processing example using FIG. 12, the point 1380, the control point a 1386, and the point 1384 are connected. In the example of FIG. 13, the point 1380, the control point a 1386, and the control point b 1388 are connected. The control point a 1386 is selected to be a point that is lower than the point 1384 that is the maximum brightness of the input color gamut 1310 by a predetermined brightness correction amount 1399. Then, the control point b1388 may be selected so as to be equal to or higher than the maximum brightness of the output color gamut 1330. Furthermore, in the saturation direction, the control point b1388 may be selected so that it is not less than the maximum saturation of the output color gamut 1330 and not more than the maximum saturation of the input color gamut 1310. For example, in order to simplify the selection process, the maximum saturation of the input color gamut 1310 may be set as the saturation of the control point b1388.
The relationship between the saturation and lightness of the control point a 1386 and the control point b 1388 is shown in the example of FIG. When the brightness correction amount is 0, the brightness of the input image signal remains as it is. That is, the corrected input color gamut 1350 corrects the brightness of the input color gamut 1310 as shown in the graph of the example of FIG. As a result of such correction, the input color gamut 1310 is corrected to a corrected input color gamut 1350 that approximates the shape of the output color gamut 1330.

A third embodiment will be described. The module configuration of the third embodiment is equivalent to the module configuration of the first embodiment or the second embodiment described above. However, modules corresponding to the input image signal correction module 120 and the input image signal correction module 1120 correct the output image signal.
A processing example according to the third embodiment will be described with reference to the example of FIG.
Correction is performed when there is a region where the lightness is higher than the maximum saturation point of the input color gamut 1510 or the special color gamut 1530 and the lightness of the special color gamut 1530 is higher than the lightness of the input color gamut 1510. This is as described above. Then, as described above, the intersection 1582 of the input color gamut 1510 and the spot color gamut 1530 is extracted.
Next, for example, a point on the spot color gamut 1530 in the area where the saturation difference is maximum in the mapping direction and the spot color gamut 1530 is wider than the input color gamut 1510 is set as the control point x1586. A control point y1588 is set to a point where a line extending from the maximum saturation point to the high lightness side of the color gamut on the southern hemisphere side (lower half) in the color space and a line passing through the white point 1580 and the control point x1586 are connected. Then, the spot color gamut 1530 from the point 1580 which is white to the control point x1586 and a line passing through the control point x1586 and the control point y1588 are set as the corrected output color gamut 1550.
However, the expanded portion generated by this correction is crushed, but the halftone gradation that is important for color reproduction is maintained.

  A hardware configuration example of the image processing apparatus according to the above-described embodiment will be described with reference to FIG. The configuration shown in FIG. 16 is configured by a personal computer (PC), for example, and shows a hardware configuration example including a data reading unit 1617 such as a scanner and a data output unit 1618 such as a printer.

  A CPU (Central Processing Unit) 1601 includes various modules described in the above-described embodiments, that is, the input color space conversion module 110, the input image signal correction module 120, the mapping module 140, the output color space conversion module 150, and the like. It is a control part which performs the process according to the computer program which described the execution sequence of a module.

  A ROM (Read Only Memory) 1602 stores programs, calculation parameters, and the like used by the CPU 1601. A RAM (Random Access Memory) 1603 stores programs used in the execution of the CPU 1601, parameters that change as appropriate during the execution, and the like. These are connected to each other by a host bus 1604 including a CPU bus.

  The host bus 1604 is connected to an external bus 1606 such as a PCI (Peripheral Component Interconnect / Interface) bus via a bridge 1605.

  A keyboard 1608 and a pointing device 1609 such as a mouse are input devices operated by an operator. The display 1610 includes a liquid crystal display device or a CRT (Cathode Ray Tube), and displays various types of information as text or image information.

  An HDD (Hard Disk Drive) 1611 includes a hard disk, drives the hard disk, and records or reproduces a program executed by the CPU 1601 and information. The hard disk includes an input image signal 105, an output image signal 195, input color gamut information 132, output color gamut information 134, input color gamut information 1132, output color gamut information A (special color) 1134, and output color gamut information B (basic color). 1136 and the like are stored. Further, various computer programs such as various other data processing programs are stored.

  The drive 1612 reads data or a program recorded on a removable recording medium 1613 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory, and the data or program is read out from the interface 1607 and the external bus 1606. , A bridge 1605, and a RAM 1603 connected via the host bus 1604. The removable recording medium 1613 can also be used as a data recording area similar to the hard disk.

  The connection port 1614 is a port for connecting an external connection device 1615 and has a connection unit such as USB, IEEE1394. The connection port 1614 is connected to the CPU 1601 and the like via the interface 1607, the external bus 1606, the bridge 1605, the host bus 1604, and the like. A communication unit 1616 is connected to a communication line and executes data communication processing with the outside. The data reading unit 1617 is a scanner, for example, and executes document reading processing. The data output unit 1618 is a printer, for example, and executes document data output processing.

  Note that the hardware configuration of the image processing apparatus shown in FIG. 16 shows one configuration example, and the present embodiment is not limited to the configuration shown in FIG. 16, and the modules described in this embodiment are executed. Any configuration is possible. For example, some modules may be configured with dedicated hardware (for example, Application Specific Integrated Circuit (ASIC), etc.), and some modules are in an external system and connected via a communication line In addition, a plurality of systems shown in FIG. 16 may be connected to each other via communication lines so as to cooperate with each other. Further, it may be incorporated in a copying machine, a fax machine, a scanner, a printer, a multifunction machine (an image processing apparatus having any two or more functions of a scanner, a printer, a copying machine, a fax machine, etc.).

In the above-described embodiment, the example in which the second image device expresses an image by using a basic color and a color material other than the basic color has been described. However, the first color gamut or the second color device Any area may be used as long as the brightness is higher than the point of maximum saturation of the color gamut and the brightness of the second color gamut is higher than the brightness of the first color gamut. For example, the present invention can also be applied to a case where such a relationship occurs when the user edits an image with retouching software or the like.
Further, the color conversion correction coefficient may be generated by performing the above-described correction processing. The color conversion correction coefficient is used when the first image signal is converted into the second image signal, and by using the color conversion correction coefficient, it is possible to perform the same as the correction processing described above. become.

The program described above may be provided by being stored in a recording medium, or the program may be provided by communication means. In that case, for example, the above-described program may be regarded as an invention of a “computer-readable recording medium recording the program”.
The “computer-readable recording medium on which a program is recorded” refers to a computer-readable recording medium on which a program is recorded, which is used for program installation, execution, program distribution, and the like.
The recording medium is, for example, a digital versatile disc (DVD), which is a standard established by the DVD Forum, such as “DVD-R, DVD-RW, DVD-RAM,” and DVD + RW. Standard “DVD + R, DVD + RW, etc.”, compact disc (CD), read-only memory (CD-ROM), CD recordable (CD-R), CD rewritable (CD-RW), Blu-ray disc ( Blu-ray Disc (registered trademark), magneto-optical disk (MO), flexible disk (FD), magnetic tape, hard disk, read-only memory (ROM), electrically erasable and rewritable read-only memory (EEPROM (registered trademark)) )), Flash memory, Random access memory (RAM) SD (Secure Digital) memory card and the like.
The program or a part of the program may be recorded on the recording medium for storage or distribution. Also, by communication, for example, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a wired network used for the Internet, an intranet, an extranet, etc., or wireless communication It may be transmitted using a transmission medium such as a network or a combination of these, or may be carried on a carrier wave.
Furthermore, the program may be a part of another program, or may be recorded on a recording medium together with a separate program. Moreover, it may be divided and recorded on a plurality of recording media. Further, it may be recorded in any manner as long as it can be restored, such as compression or encryption.

DESCRIPTION OF SYMBOLS 105 ... Input image signal 110 ... Input color space conversion module 120 ... Input image signal correction module 130 ... Color gamut information storage module 132 ... Input gamut information 134 ... Output color gamut information 140 ... Mapping module 150 ... Output color space conversion module 1120 ... Input image signal correction module 1130 ... Color gamut information storage module

Claims (11)

First conversion means for converting a first image signal handled by the first image device into an image signal of a predetermined color space;
Based on the first color gamut information indicating the first color gamut that can be expressed by the first image device and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the image signal converted by the first conversion means;
Mapping means for mapping the image signal corrected by the correction means into the second color gamut;
Second conversion means for converting the image signal mapped by the mapping means into a second image signal handled by the second image device ;
The correction unit extracts a point where the first color gamut and the second color gamut intersect, and the first color gamut and the second color gamut in a region having a higher brightness than the intersecting point. An image processing apparatus that generates a control point on the side where the brightness is higher than the second color gamut based on the distance between the two color gamuts and corrects the image signal so as to pass through the control point . The image processing apparatus according to claim 1, wherein the second image device represents an image with a basic color and a color material of a color other than the basic color. The correction means is a region having a lightness higher than a point of maximum saturation of the first color gamut or the second color gamut, and the lightness of the second color gamut is the same as the first color gamut. Performing the correction when there is a region higher than the lightness of the color gamut of the second color gamut or when there is a region where the saturation of the second color gamut is higher than the saturation of the first color gamut at the same lightness. The image processing apparatus according to claim 1, wherein the image processing apparatus is an image processing apparatus. The correcting unit extracts a point where the first color gamut and the second color gamut intersect, and a color gamut based on the basic color and a second color gamut in a region having a higher brightness than the intersecting point. based on the distance between, than the second color gamut to generate a control point on a side brightness is high, according to claim 2 or claims and correcting an image signal so as to pass through the control points The image processing apparatus according to claim 3 , which is dependent on item 2 . First conversion means for converting a first image signal handled by the first image device into an image signal of a predetermined color space;
Based on the first color gamut information indicating the first color gamut that can be expressed by the first image device and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the image signal converted by the first conversion means;
Mapping means for mapping the image signal corrected by the correction means into the second color gamut;
Second conversion means for converting the image signal mapped by the mapping means into a second image signal handled by the second image device ;
The second image device represents an image with a basic color and a color material of a color other than the basic color,
The correcting unit extracts a point where the first color gamut and the second color gamut intersect, and a color gamut based on the basic color and a second color gamut in a region having a higher brightness than the intersecting point. An image processing apparatus that generates a control point on the side where the brightness is higher than the second color gamut based on the distance between the two color gamuts and corrects the image signal so as to pass through the control point . The correction means is a region having a lightness higher than a point of maximum saturation of the first color gamut or the second color gamut, and the lightness of the second color gamut is the same as the first color gamut. Performing the correction when there is a region higher than the lightness of the color gamut of the second color gamut or when there is a region where the saturation of the second color gamut is higher than the saturation of the first color gamut at the same lightness. The image processing apparatus according to claim 5 , wherein: The correction unit extracts a point where the first color gamut and the second color gamut intersect, and the first color gamut and the second color gamut in a region having a higher brightness than the intersecting point. based on the distance between, than the second color gamut to generate a control point on a side brightness is high, according to claim 5 or and corrects an image signal so as to pass through the control points 6 An image processing apparatus according to 1. It said correction means, the image processing apparatus according to any one of claims 1 to 7, characterized in that to correct the second image signal. It said correction means, the image processing apparatus according to any one of claims 1 8, characterized in that generating a color conversion correction coefficient. Computer
First conversion means for converting a first image signal handled by the first image device into an image signal of a predetermined color space;
Based on the first color gamut information indicating the first color gamut that can be expressed by the first image device and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the image signal converted by the first conversion means;
Mapping means for mapping the image signal corrected by the correction means into the second color gamut;
Functioning as second conversion means for converting the image signal mapped by the mapping means into a second image signal handled by the second image equipment ;
The correction unit extracts a point where the first color gamut and the second color gamut intersect, and the first color gamut and the second color gamut in a region having a higher brightness than the intersecting point. A control point is generated on the side where the brightness is higher than the second color gamut based on the distance between and the image signal is corrected so as to pass through the control point
An image processing program characterized by that . Computer
First conversion means for converting a first image signal handled by the first image device into an image signal of a predetermined color space;
Based on the first color gamut information indicating the first color gamut that can be expressed by the first image device and the second color gamut information indicating the second color gamut that can be expressed by the second image device. Correction means for correcting the image signal converted by the first conversion means;
Mapping means for mapping the image signal corrected by the correction means into the second color gamut;
Functioning as second conversion means for converting the image signal mapped by the mapping means into a second image signal handled by the second image equipment ;
The second image device represents an image with a basic color and a color material of a color other than the basic color,
The correcting unit extracts a point where the first color gamut and the second color gamut intersect, and a color gamut based on the basic color and a second color gamut in a region having a higher brightness than the intersecting point. A control point is generated on the side where the brightness is higher than the second color gamut based on the distance between and the image signal is corrected so as to pass through the control point
An image processing program characterized by that .

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