JP6684164B2 - Color processing device and color processing method - Google Patents

Description

  The present invention relates to a color matching technique for matching color reproduction between devices.

  The format of an ICC profile that expresses the color characteristics of a device in performing color matching is defined by INTERNATIONAL COLOR CONSORTIUM. The device characteristics are described in the standard ICC format, and by using the color matching module corresponding to the ICC profile, color matching can be performed with an arbitrary combination of the input device and the output device.

  In color matching, a conversion table is created from the given input profile, output profile, and information on the gamut compression type, and output image data for the input image data is calculated using the created conversion table.

  Although the standard ICC format has versatility, for example, even when the conversion by the input profile and the output profile that performs the inverse conversion have the same characteristic originally, the calculation error may occur due to the creation of the conversion table. In addition, there is a problem that it takes a long time to perform image conversion using the conversion table.

  There is a conventional technique in which the module of the color matching calling side determines whether the file names of the input profile and the output profile match, or determines that the input and output profile data match in binary, and skips the color matching process when they match. .

JP 2006-197395 JP 2009-200909 JP JP 2009-200930 JP

  However, the method of skipping conversion when the input profile and the output profile match in the above-mentioned conventional technique does not consider the color gamut compression by the color gamut compression type (rendering intent). Therefore, the color matching process specified by the color gamut compression type is not executed. Further, even if the profiles have the same characteristics, there is a problem that the conversion cannot be skipped when the binary does not match.

  The present invention has been made in view of such a problem, and provides a technique for appropriately determining whether or not color conversion can be skipped in color matching without excess or deficiency.

According to one aspect of the present invention, a first determination unit that determines whether or not the number of channels in the first color conversion profile and the number of channels in the second color conversion profile match.
Second determining means for determining whether or not the color reproduction characteristic defined by the first color conversion profile and the color reproduction characteristic defined by the second color conversion profile match;
When it is determined that the first determining unit and the second determining unit match each other, color conversion is performed instead of the color conversion table based on the first color conversion profile and the second color conversion profile. And an output unit that outputs information indicating that can be omitted.

  According to the configuration of the present invention, whether or not color conversion can be skipped in color matching can be appropriately determined without excess or deficiency. As a result, it is possible to prevent the occurrence of a calculation error due to color conversion and reduce the processing time.

FIG. 3 is a block diagram showing a functional configuration example of a color processing device. The flowchart of the process which the production | generation part 13 performs. The figure which shows an example of matrix type profile data. The flowchart of the process which the production | generation part 13 performs. Explanatory drawing of the conversion data breakdown included in a tag, the figure which shows the hardware structural example of a computer device. The figure which shows an example of a LUT type profile. The flowchart of the process which the production | generation part 13 performs. The figure which shows an example of a LUT type profile. The figure which shows an example of GUI.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the embodiment described below shows an example of the case where the present invention is specifically implemented, and is one of the specific examples of the configurations described in the claims.

[First Embodiment]
In this embodiment, an example of a color processing device having the following configuration will be described. That is, it is determined whether or not the number of channels in the first color conversion profile matches the number of channels in the second color conversion profile (first determination). Further, it is determined whether or not the color reproduction characteristic defined by the first color conversion profile and the color reproduction characteristic defined by the second color conversion profile match (second determination). When it is determined that the first and second determinations match, color conversion can be omitted instead of the color conversion table based on the first color conversion profile and the second color conversion profile. Outputs information indicating that there is. In the present embodiment, it is assumed that all profiles are ICC format profiles.

  First, a functional configuration example of the color processing apparatus according to this embodiment will be described with reference to the block diagram of FIG. In the configuration shown in FIG. 1, a color conversion table is generated in the color processing apparatus from a profile corresponding to one device and a profile corresponding to the other device, and color conversion of an image is performed using the generated table. It shows an example of a configuration for performing.

  The generation unit 13 includes an input profile 10 corresponding to one device (device A), an output profile 12 corresponding to the other device (device B), and gamut compression that is information that defines the type of gamut compression. Type 11 and are input. In the present embodiment, the generation unit 13 uses the input profile 10, the output profile 12, and the color gamut compression type 11 to convert a color in the color space of the device A into a color in the color space of the device B. 14 is generated. The image conversion unit 16 generates, as an output image 17, an image obtained by converting the color of the input image 15, which is an image to be subjected to color conversion, using the conversion table 14. The processing performed by the generation unit 13 will be described with reference to the flowchart of FIG.

  In step S21, the determination unit 131 refers to the tag table of the input profile 10 and the tag table of the output profile 12 to determine whether both the input profile 10 and the output profile 12 are gray profiles. For example, when the kTRC tag is included in the tag table of the input profile 10 (output profile 12), the input profile 10 (output profile 12) is determined to be the gray profile. If the input profile 10 and the output profile 12 are gray profiles, the process proceeds to step S22. If at least one of the input profile 10 and the output profile 12 is not a gray profile, the process proceeds to step S23.

  In step S22, the acquisition unit 132 acquires the tag element data from the input profile 10 and the tag element data from the output profile 12. The tag element data is data having contents corresponding to each item indicated by the tag table. Then, the determination unit 131 determines whether the gray tone reproduction curve defined by the tag element data of the input profile 10 and the gray tone reproduction curve defined by the tag element data of the output profile 12 match. To judge. If the result of this determination is that they match, the process proceeds to step S27, and if they do not match, the process proceeds to step S25.

  In step S27, the setting unit 134 outputs information (skip information) indicating that color conversion can be skipped. For example, the information indicating the identity conversion may be output as the skip information as the information of the conversion table, or the skip information may be output to the control unit that operates the generation unit 13 to control the control unit. You may make it judge whether to skip color conversion.

  In step S25, the creation unit 133 uses the input profile 10, the output profile 12, and the color gamut compression type 11 to create the conversion table 14 for converting the color in the color space of the device A into the color in the color space of the device B. To generate. A technique for generating a conversion table for color conversion using two profiles and the color gamut compression type 11 is well known, and therefore the description thereof will be omitted. The color gamut compression type 11 is not essential, and may not be used depending on the situation.

  In step S26, the approximation determination unit 135 determines whether the number of channels in the input profile 10 (for example, each channel of R, G, B) and the number of channels in the output profile 12 match. Further, the approximation determination unit 135 determines whether or not the amount of color change before and after the color conversion using the conversion table 14 generated in step S25 is less than the specified value. For example, each of a plurality of input colors (for example, 256 colors) is converted using the conversion table 14 to obtain a corresponding output color. Then, for each of the plurality of input colors, the difference (absolute value) from the corresponding output color is obtained, and the sum is defined as the above “color change amount”, and whether or not the color change amount is less than the specified value. To judge. When the number of channels in the input profile 10 matches the number of channels in the output profile 12 and the condition that the amount of color change is less than the specified value is satisfied, the color conversion by the conversion table 14 can be skipped. It is determined and the process proceeds to step S27. On the other hand, if the condition is not satisfied (the number of channels in the input profile 10 does not match the number of channels in the output profile 12 or the amount of color change is equal to or more than the specified value), the setting unit 134 determines in step S25. The generated conversion table 14 is output.

  On the other hand, in step S23, the determination unit 131 refers to the tag table of the input profile 10 and the tag table of the output profile 12 to determine whether both the input profile 10 and the output profile 12 are matrix profiles. . For example, if the tag table of the input profile 10 (output profile 12) includes rTRC, gTRC, bTRC, rXYZ, gXYZ, bXYZ tags, it is determined that the input profile 10 (output profile 12) is a matrix profile. If the input profile 10 and the output profile 12 are matrix-type profiles, the process proceeds to step S24. If at least one of the input profile 10 and the output profile 12 is not a matrix-type profile, the process proceeds to step S25.

  In step S24, the acquisition unit 132 acquires the tag element data from the input profile 10 and the tag element data from the output profile 12. Then, the determination unit 131 determines that the gradation reproduction curve and the determinant defined by the tag element data of the input profile 10 match the gradation reproduction curve and the determinant defined by the tag element data of the output profile 12, respectively. Determine whether to do. This determination is performed for all channels (for example, R, G, B channels) in the input profile 10 (output profile 12). If the result of this determination is that all channels match, the process proceeds to step S27, and if there is no match in at least one channel, the process proceeds to step S25.

  An example of two matrix type profile data in the ICC format is shown in FIG. The structure of an ICC format profile is roughly divided into a profile header section, a tag table, and tag element data.

  When the profile 3A is applied as the input profile 10 and the profile 3B is applied as the output profile 12, it is determined in step S23 whether or not both profiles include rTRC, gTRC, bTRC, rXYZ, gXYZ, bXYZ tags. In the case of FIG. 3, both profiles include rTRC, gTRC, bTRC, rXYZ, gXYZ, and bXYZ tags, so it is determined that both profiles are matrix-type profiles. The profile 3A and the profile 3B are different in profile, but the profile characteristics are the same. That is, the arrangement of the tag tables is different between the profile 3A and the profile 3B. However, the respective elements of the rTRC, gTRC, bTRC, rXYZ, gXYZ, and bXYZ tags are the same in profile 3A and profile 3B, and the profile characteristics should be judged to be the same. However, in this embodiment, when the profile 3A is applied as the input profile 10 and the profile 3B is applied as the output profile 12, the color conversion is set to be skipped.

  When the conversion table 14 is output from the generation unit 13, the image conversion unit 16 outputs an image obtained by converting the input image 15 using the conversion table 14 as an output image 17. On the other hand, when the skip information is output from the generation unit 13, the image conversion unit 16 skips the color conversion of the input image 15 and outputs the input image 15 as the output image 17.

[Second Embodiment]
Hereinafter, the difference from the first embodiment will be mainly described, and the description will be made assuming that it is the same as that of the first embodiment unless otherwise mentioned below. The operation of the generation unit 13 according to this embodiment will be described with reference to the flowchart of FIG.

  In step S41, the determination unit 131 refers to the tag table of the input profile 10 and the tag table of the output profile 12, and determines whether both the input profile 10 and the output profile 12 are LUT type profiles. As a result of this determination, if both the input profile 10 and the output profile 12 are LUT type profiles, the process proceeds to step S42, and if at least one is not the LUT type profile, the process proceeds to step S45.

  In step S42, the determination unit 131 determines whether the number of channels in the input profile 10 and the number of channels in the output profile 12 match. As a result of this determination, if they match, the process proceeds to step S43, and if they do not match, the process proceeds to step S45.

  In step S43, the determination unit 131 determines whether or not the color gamut compression type 11 indicates colorimetric color reproduction (Colorimetric). If the result of this determination is that the color gamut compression type 11 indicates colorimetric color reproduction, the process proceeds to step S44, and it is determined that the color gamut compression type 11 is colorimetric color reproduction. If not shown, the process proceeds to step S45.

  In step S44, the acquisition unit 132 acquires the tag element data from the input profile 10 and the tag element data from the output profile 12. The determination unit 131 then determines the “colorimetric characteristic from the color space of the device A to the PCS” specified by the tag element data of the input profile 10 and the “color space of the device B to PCS specified by the tag element data of the output profile 12. And "the colorimetric characteristics to" are matched. PCS is an abbreviation for Profile Connection Space. As a result of this determination, if they match, the process proceeds to step S47, and if they do not match, the process proceeds to step S45. In steps S45, S46 and S47, the same processes as steps S25, S26 and S27 described above are performed, respectively.

  In the case of the ICC format, the tag referred to by the determination unit 131 is the A2B1 (D2B1) tag which is a colorimetric color reproduction tag, and the A2B0 (D2B0) tag when there is no A2B1 (D2B1) tag.

  FIGS. 5A and 5B show examples of conversion data included in the ICC format A2B0 tag and B2A0 tag. Conversion data of device color space → PCS is set in the A2Bx tag, and is conversion data for converting a colorimetric value of a color actually displayed or output on the device into a color value in PCS. Although the conversion data of PCS → device color space is set in the B2Ax tag, a conversion element of PCS → device color space in which the colorimetric value is inversely converted except for B2A1 whose color gamut compression type is colorimetric color reproduction. In addition, it includes a conversion element for Lab-to-Lab color gamut compression that is a PCS. Therefore, in cases other than colorimetric color reproduction, even if the input profile and the output profile are the same, color gamut compression is performed when color matching is performed on the input image, and therefore the output images do not match. In this embodiment, color conversion is not skipped when the color gamut compression type 11 is not colorimetric color reproduction.

  FIG. 6 is a diagram showing an example of two LUT type profiles in the ICC format. The profile 6A and the profile 6B are different in profile, and the tag element data of the A2Bx tag indicating the correspondence between the device color space and the PCS match, and the tag element of the B2Ax tag indicating the correspondence between the PCS and the device color space. The data do not match. It is generally possible that the B2A1 tags do not match even though the A2B1 tags whose color gamut compression type is colorimetric color reproduction match. For example, this is a case where a profile creation patch chart is printed on a certain printer, and two profiles are created by different profile creation tools based on common colorimetric data obtained by measuring the color of the patch chart. Since the colorimetric data is the same, the correspondence between the device color space and the PCS is the same, but when the correspondence between the PCS and the device color space is created, it is generated due to the difference in the printer model assumed by each profile creation tool. The tables played will change.

  In the present embodiment, even if the B2A1 tags are different as in the above example, if the A2B1 tags match, the colorimetric values are the same, so it is determined that the profiles have the same characteristics, and processing for skipping color conversion (step S47). The color conversion skip is realized by.

[Third Embodiment]
The operation of the generation unit 13 according to this embodiment will be described with reference to the flowchart of FIG. 7. The processes in steps S71 to S74 are the same as steps S41 to S44 in FIG.

  In step S75, the acquisition unit 132 acquires the tag element data from the input profile 10 and the tag element data from the output profile 12. The determination unit 131 then determines the “colorimetric characteristic from the PCS to the color space of the device A” defined by the tag element data of the input profile 10 and the “PCS to the color space of the device B” defined by the tag element data of the output profile 12. And "the colorimetric characteristics to" are matched. As a result of this determination, if they match, the process proceeds to step S78, and if they do not match, the process proceeds to step S76. In steps S76, S77 and S78, the same processes as steps S25, S26 and S27 described above are performed.

  In the case of the ICC format, the data referred to by the determination unit 131 are the A2B1 (D2B1) and B2A1 (B2D1) tags, and the A2B0 (D2B0) and B2A0 (B2D0) tags when the tag on the left does not exist.

  FIG. 8 is a diagram showing an example of two LUT type profiles in the ICC format. The profile 8A and the profile 8B are different in profile. The tag element data of the A2Bx tag indicating the correspondence between the device color space and the PCS match, the tag element data of the B2A1 tag indicating the correspondence between the PCS and the device color space match, and the tag element data of the B2A0 and B2A2 tags match. do not do.

  According to the present embodiment, even if the profiles are different as in the above example, when the color gamut compression type 11 is colorimetric color reproduction, the tag element data of the A2B1 and B2A1 tags match, so profiles with the same characteristics. And the skip of color conversion is realized. In this embodiment, if the tag element data of the B2A1 tag is different, it is not determined that the profiles have the same characteristics, and the conversion table is created, which is different from the above-described embodiments.

[Fourth Embodiment]
FIG. 9 shows an example of a GUI (graphical user interface) for setting the input profile 10, the output profile 12, the color gamut compression type 11, and whether or not the above processing by the generation unit 13 is performed. The GUI shown in FIG. 9 is displayed on the screen of the display unit 505 included in the color processing apparatus.

  When the color space of the input image is RGB, the user operates the operation unit 504 to specify the pull-down menu 91 to display a list of RGB profiles, and perform an operation of selecting one from the list. When the color space of the input image is CMYK, the user operates the operation unit 504 to specify the pull-down menu 92 to display a list of CMYK profiles, and to select one from the list. As described above, by operating the pull-down menu 91 or 92, the default input profile used as the input profile 10 can be designated when the profile is not associated with the input image.

  In addition, the user operates the operation unit 504 to specify the pull-down menu 93 to display a plurality of types of color gamut compression, and selects one from the types. The selected type is the color gamut compression type 11.

  In addition, the user operates the operation unit 504 to specify the pull-down menu 94 to display a plurality of output profiles and perform an operation of selecting one from the output profiles. This selected output profile becomes the output profile 12. Note that the setting "device standard" does not indicate a specific profile, but indicates that when an output device is designated, the profile set as the default for that device is used.

  When the user operates the operation unit 504 and selects Auto with the radio button 95, the generation unit 13 performs the above operation, and when OFF is selected, the generation unit 13 does not perform the above operation and the conversion table 14 is always displayed. Will be created.

  Further, when ON is selected by the radio button 95, colorimetric color reproduction is limited in the second and third embodiments, but there is a possibility of skipping in any color gamut compression type by removing the condition. As a result, when the user specifies from the user interface, the skip applicable range can be expanded.

[Fifth Embodiment]
Although both the generation unit 13 and the image conversion unit 16 in FIG. 1 may be implemented by dedicated hardware, these functional units may be implemented by software (computer program). In this case, a computer device that can execute this computer program can be applied to the color processing devices according to the first to fourth embodiments. A hardware configuration example of a computer device applicable to the color processing devices according to the first to fourth embodiments will be described with reference to the block diagram of FIG.

  The CPU 501 executes processing using computer programs and data stored in the RAM 502 and ROM 503. As a result, the CPU 501 can control the operation of the entire computer device, and can also execute or control each of the processes described above as being performed by the color processing device to which the computer device is applied.

  The RAM 502 has an area for storing computer programs and data loaded from the external storage device 506 and data received from the outside via the I / F (interface) 507. The RAM 502 also has a work area used when the CPU 501 executes various processes. In this way, the RAM 502 can provide various areas as needed. The ROM 503 stores setting data, a boot program, and the like of this apparatus that do not require rewriting.

  The operation unit 504 is composed of a user interface such as a keyboard and a mouse, and can be operated by the user to input various instructions to the CPU 501. For example, the user can operate the operation unit 504 to operate the GUI shown in FIG. 9.

  The display unit 505 is composed of a CRT, a liquid crystal screen, or the like, and can display the processing result by the CPU 501 as an image or characters. For example, the GUI shown in FIG. 9 is displayed on the display unit 505. The operation unit 504 and the display unit 505 may be integrated to form a touch panel screen.

  The external storage device 506 is a large capacity information storage device represented by a hard disk drive device. The external storage device 506 stores an OS (operating system) and computer programs and data for causing the CPU 501 to execute or control the above-described processes performed by the color processing device. The computer program stored in the external storage device 506 includes a computer program for causing the CPU 501 to execute or control the processes described above as being performed by the functional units of the generation unit 13 and the image conversion unit 16. . In addition, the data stored in the external storage device 506 includes various profiles including the input profile 10 and the output profile 12, the gamut compression type 11, the input image 15, and the information known in the above description. include. Computer programs and data stored in the external storage device 506 are appropriately loaded into the RAM 502 under the control of the CPU 501 and are to be processed by the CPU 501.

  The I / F 507 performs data communication with an external device. For example, the input image 15, the input profile 10, the output profile 12, and the gamut compression type 11 may be acquired from the external device to the RAM 502 or the external storage device 506 via the I / F 507.

  The CPU 501, the RAM 502, the ROM 503, the operation unit 504, the display unit 505, the external storage device 506, and the I / F 507 are all connected to the bus 508. In addition, the configuration illustrated in FIG. 5C or the configuration having the same or more functions than this may be mounted in a digital camera, a printer, or the like as an embedded device. Further, in the first to fifth embodiments, some or all of them may be appropriately combined and used, or may be selectively used.

(Other embodiments)
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by the processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  131: determination unit 132: acquisition unit 133: creation unit 134: setting unit 135: approximation determination unit

Claims (14)

First determining means for determining whether or not the number of channels in the first color conversion profile and the number of channels in the second color conversion profile match;
Second determining means for determining whether or not the color reproduction characteristic defined by the first color conversion profile and the color reproduction characteristic defined by the second color conversion profile match;
When it is determined that the first determining unit and the second determining unit match each other, color conversion is performed instead of the color conversion table based on the first color conversion profile and the second color conversion profile. An output unit that outputs information indicating that the color processing can be omitted.   When the first color conversion profile and the second color conversion profile are gray profiles, the second judgment means defines a gray gradation reproduction curve defined by the first color conversion profile, and The color processing apparatus according to claim 1, wherein it is determined whether or not the gray gradation reproduction curve defined by the second color conversion profile matches.   If the gray gradation reproduction curve defined by the first color conversion profile and the gray gradation reproduction curve defined by the second color conversion profile match, the output means replaces the table. The color processing apparatus according to claim 2, wherein the table is generated when the information is output to, and when the information does not match.   The second determination means, when the first color conversion profile and the second color conversion profile are matrix-type profiles, a gradation reproduction curve and a determinant defined by the first color conversion profile. The color processing according to any one of claims 1 to 3, wherein is determined whether or not the color reproduction curve and the determinant are defined by the second color conversion profile. apparatus.   The output means satisfies the condition that the gradation reproduction curve and the determinant defined by the first color conversion profile match the gradation reproduction curve and the determinant specified by the second color conversion profile, respectively. The color processing apparatus according to claim 4, wherein the information is output instead of the table when the above condition is satisfied, and the table is generated when the condition is not satisfied.   When the first color conversion profile and the second color conversion profile are LUT-type profiles and the type of gamut compression is colorimetric color reproduction, the second determination means determines the first 6. The method according to claim 1, wherein it is determined whether or not the colorimetric characteristic of the PCS based on the color conversion profile and the colorimetric characteristic of the PCS based on the second color conversion profile match. The color processing device according to item 1.   The output unit has a colorimetric color reproduction as the color gamut compression type, and has a colorimetric characteristic for PCS according to the first color conversion profile and a colorimetric characteristic for PCS according to the second color conversion profile. The information is output instead of the table when the condition that the characteristics match is satisfied, and the table is generated when the condition is not satisfied. Color processing device.   When the first color conversion profile and the second color conversion profile are LUT-type profiles and the type of gamut compression is colorimetric color reproduction, the second determination means determines the first Between the color space of the device corresponding to the color conversion profile and the PCS, the colorimetric characteristics defined by the first color conversion profile and the color space of the device corresponding to the second color conversion profile and the PCS. 6. The color processing apparatus according to claim 1, wherein it is determined whether or not the colorimetric characteristics defined by the second color conversion profile match with each other.   The output means defines the color gamut compression type is colorimetric color reproduction and the first color conversion profile defines between the color space of the device corresponding to the first color conversion profile and the PCS. The condition that the colorimetric characteristics match the colorimetric characteristics defined by the second color conversion profile between the device color space corresponding to the second color conversion profile and the PCS is satisfied. The color processing apparatus according to claim 8, wherein the information is output instead of the table in the case of the above, and the table is generated in the case where the condition is not satisfied.   The output means outputs the table when the change in the color value due to the color conversion using the table is a specified value or more, and when the change is less than the specified value, the table is replaced. The color processing apparatus according to claim 1, wherein the information is output to the. Furthermore,
When the output means outputs the table, color conversion using the table is performed on the input image, and when the output means outputs the information, color conversion is performed on the input image. The color processing apparatus according to claim 1, further comprising a non-execution unit. An instruction means for instructing whether or not to make the determination by the first determination means and the second determination means,
When the instructing unit instructs the first determining unit and the second determining unit not to perform the determination, the first determining unit and the second determining unit do not perform the determination, and the output unit Generates the table, the color processing apparatus according to claim 1. A color processing method performed by a color processing device,
A first determination step of the first determination means of the color processing device, which determines whether or not the number of channels in the first color conversion profile and the number of channels in the second color conversion profile match;
A second determination means of the color processing device determines whether or not the color reproduction characteristic defined by the first color conversion profile and the color reproduction characteristic defined by the second color conversion profile match. A second determination step to
When the output means of the color processing device determines that they match in the first determination step and the second determination step, color conversion based on the first color conversion profile and the second color conversion profile An output step of outputting information indicating that the color conversion can be omitted, instead of the table for the color processing.   A computer program for causing a computer to function as each unit of the color processing apparatus according to claim 1.

Images