JP4970419B2 - Image processing device - Google Patents

Description

  The present invention relates to an image processing device that converts image data in an input color gamut in an input device into image data in an output color gamut in an output device, and more particularly to an image processing device that performs color conversion between an input color gamut and an output color gamut. Is.

Conventionally, when converting image data in the input device into image data in the output device, a process called color gamut mapping is performed to reproduce the image data in the input color gamut in the input device within the output color gamut in the output device.
In the above color gamut mapping, the color gamut mapping parameter is generally determined by uniquely associating the color gamut of the output device with the color gamut of the input device, and for the input color gamut. The output color gamut is often small. In this way, if the output color gamut is smaller than the input color gamut, the degree of mapping compression during color gamut mapping increases, so the entire color gamut maintains the gradation of saturation and lightness, and the output color space In the color gamut mapping that maps to the gamut, there is a problem that the saturation is significantly lowered, and preferable color reproduction cannot be performed.

In view of such a problem, Patent Document 1 has been proposed as a color gamut mapping process capable of realizing a preferable color reproduction in which a decrease in saturation is suppressed. Patent Document 1 analyzes the color gamut of input image data, and calculates the input image data from color gamut information stored in advance and a color conversion profile in which the color gamut mapping parameters associated with each color gamut information are optimized. The minimum color gamut information including the used color gamut and the color conversion profile associated with the minimum color gamut information are selected, and the output image data is generated by performing color conversion processing on the input image data using the color conversion profile. Is.
JP 2007-166403 A

  However, in the case of Patent Document 1, if the used color gamut of the input image data is different, the corresponding color gamut mapping parameter is changed, so that even the same input color is reproduced in a different color.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image processing apparatus that can reproduce the same color for the same input color.

  That is, according to the present invention, in an image processing device that converts image data in the input color gamut of the input device into image data in the output color gamut of the output device, the first image gamut information relating to the first image data input last time is stored. A first information storage unit, an image color gamut analysis unit that calculates second image color gamut information relating to the second image data input this time, a second image data and a second image color information that stores the second image color gamut information. Two information storage units, a similarity calculation unit for obtaining a similarity between the first image gamut information and the second image gamut information, and the first image color if the similarity is within a predetermined similarity range. If the gamut information is used as the gamut of the input device used for the gamut mapping, and the similarity is outside the predetermined similarity range, the second image gamut information is used as the gamut of the input device used for the gamut mapping. Used for color conversion color gamut determination unit and the above color gamut mapping A color gamut mapping unit for generating color gamut mapping image data in which the color of the second image data is mapped into the color gamut of the output device based on the input color gamut and the color gamut of the output device. It is a feature.

  According to another aspect of the present invention, in an image processing device that converts image data in an input color gamut in an input device into image data in an output color gamut in an output device, first image gamut information relating to the first image data input last time is obtained. A first information storage unit for storing; an image color gamut analysis unit for calculating second image color gamut information relating to the second image data input this time; and the second image data and the second image color gamut information. First color gamut mapping image data obtained by mapping the color of the second image data into the color gamut of the output device based on the second information storage unit, the first image color gamut information and the color gamut of the output device. And a color for generating second color gamut mapping image data in which the color of the second image data is mapped into the color gamut of the output device based on the second image color gamut information and the color gamut of the output device. Area mapping section and the first color gamut A data storage unit that stores the image image data and the second color gamut mapping image data, and a difference image generation unit that generates a difference image between the first color gamut mapping image data and the second color gamut mapping image data. The difference image is used as a criterion for selecting either the first color gamut mapping image data or the second color gamut mapping image data as output image data of the output device.

  According to the present invention, since the same color conversion color gamut is set for images having similar reproduction color gamuts of input image data, the same color reproduction can be performed for the same input colors. It is possible to eliminate the inconvenience that the input color is reproduced with a different color.

  Further, according to another invention, the first color gamut mapping image data obtained by performing the same color reproduction as the color gamut mapping processing for the previous input image is different from the previous color reproduction, but the gradation is optimum for the input image. A difference image with the second color gamut mapping image data that has been converted to be generated is generated, and either the first color gamut mapping image data or the second color gamut mapping image data is output as the difference image. Since the determination criterion for selecting as data is used, the user can visually confirm the gradation of the displayed difference image and each color gamut mapping image while checking the preferred mapping image among the above color gamut mapping images. Can be selected and output from the output device.

  Hereinafter, an embodiment of an image processing apparatus according to the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram illustrating a schematic configuration of the image processing apparatus according to the first embodiment.
As shown in FIG. 1, the image processing apparatus 300 according to the present embodiment includes a CPU 32, and an input / output I / F 31, a program ROM 33, a RAM 34, an HDD 35, and the like are connected to the CPU 32.
The program ROM 33 stores a program relating to image processing. The CPU 32 develops the image processing program stored in the program ROM 33 on the RAM 34 and executes the program, whereby the processing operation of the image processing apparatus 300 is performed. Is called.
The HDD 35 is used as a storage medium for storing various data necessary for processing of the image processing apparatus 300 described later, such as an image printed by a user, color gamut information of the monitor 100, and color gamut information of the printer 400.
The input / output I / F 31 is connected with a monitor 100 and a keyboard 200 as input devices, and with a printer 400 as an output device.

FIG. 2 is a functional block diagram of the image processing apparatus 300 according to the first embodiment.
The image processing apparatus 300 of this embodiment includes an input image information storage unit 301 as a second information storage unit, a monitor color gamut information storage unit 302, an image color gamut analysis unit 303, and a processing history information storage as a first information storage unit. Unit 304, similarity calculation unit 305, color conversion color gamut determination unit 306, printer color gamut information storage unit 307, color gamut mapping unit 308, color conversion table storage unit 309, color conversion unit 310, image output unit 311, and the like. . As described above, these are functional units realized by the CPU 32 executing the image processing program developed on the RAM 34.

  The input image information storage unit 301 is a functional unit that stores input image data (second image) and input image color gamut information (second image color gamut information) indicating a color range used for the input image. . The input image color gamut information is a scaling coefficient of 1.0 or less with respect to monitor color gamut information described later.

The monitor color gamut information storage unit 302 is a functional unit that stores color gamut information of the monitor 100. This monitor color gamut information is given as Lab values associated with RGB values at each sampling point by sampling RGB values corresponding to the outline of the color gamut discretely at a plurality of points.
For example, in the example of the color gamut information of the monitor 100 shown in FIG. 3, Lab values corresponding to white to red and red to black, which are discretely sampled, are stored. Similarly, sampling is performed for the entire color gamut of each hue such as green, blue, cyan, magenta, yellow, and the Lab value associated with each sampling point is stored as monitor color gamut information.

  The image color gamut analyzing unit 303 calculates the input image color gamut based on the input image data input from the input image information storage unit 301 and the monitor color gamut information input from the monitor color gamut information storage unit 302. Part. The input image color gamut indicates the range of colors used for the input image.

FIG. 5 is a process explanatory diagram of the image color gamut analyzing unit 303 and shows a hue section in the Lab space. In FIG. 5, the horizontal axis represents saturation and the vertical axis represents lightness.
The input image color gamut 603 is a color gamut similar to the monitor color gamut 601, and the color distribution 602 of the input image is entirely included in the color gamut. The input image color gamut information is a scaling coefficient of 1.0 or less calculated by the ratio (C2 / C1) of the maximum saturation C2 of the input image color gamut 603 to the maximum saturation C1 of the monitor color gamut 601. Note that the calculated input image color gamut information is stored in the input image information storage unit 301.

The processing history information storage unit 304 is a functional unit that stores previous color conversion color gamut information (first image color gamut information). The previous color conversion color gamut information indicates color conversion color gamut information used when the image processing apparatus 300 performs color gamut mapping on the previous input image. A scaling factor of 0 or less.

The similarity calculation unit 305 is similar to the color gamut of the input image color gamut information input from the input image information storage unit 301 and the color gamut of the previous color conversion color gamut information input from the processing history information storage unit 304. It is a functional unit that calculates S.
The similarity S can be calculated by Sc / Sp, where Sc is the input image color gamut information and Sp is the previous color conversion color gamut information. Accordingly, the closer the calculated similarity S value is to 1, the higher the similarity is, and the color gamut of the input image color gamut information Sc and the color gamut of the previous color conversion color gamut information Sp are similar. .

  The color conversion color gamut determining unit 306 is a functional unit that determines color conversion color gamut information of the monitor 100 used in the color gamut mapping unit 308 described later based on the similarity S input from the similarity calculation unit 305. is there. The color conversion color gamut information is a scaling coefficient for the color gamut of the monitor 100.

  If the similarity S is within a predetermined range, for example, 0.9 to 1.1, the previous color conversion color gamut information is used as color conversion color gamut information, and the similarity S is 0.9 to 1. If it is outside the range of 1, the input image color gamut information is used as color conversion color gamut information. That is, when the color distribution used for the input image is similar to the color distribution of the previously processed image, the same color conversion color gamut information as the previous time is used for the current color gamut mapping process.

The printer color gamut information storage unit 307 is a functional unit that stores color gamut information of the printer 400. This printer color gamut information is given as Lab values associated with CMYK values at each sampling point by discretely sampling CMYK values corresponding to the outline of the color gamut at a plurality of points.
For example, in the example of the color gamut information of the printer 400 shown in FIG. 4, Lab values corresponding to white to red and red to black, which are discretely sampled, are stored. Similar to the monitor color gamut information described above, each hue is sampled, and the Lab value associated with each sampling point is stored as printer color gamut information.

  The color gamut mapping unit 308 calculates temporary monitor color gamut information from the color conversion color gamut information input from the color conversion color gamut determination unit 306 and the monitor color gamut information input from the monitor color gamut information storage unit 302. In addition, by using the temporary monitor color gamut information and the printer color gamut information input from the printer color gamut information storage unit 307, the color gamut image data in which the color of the input image data is reproduced in the color gamut of the printer 400. Is a functional unit that generates

  The color conversion table storage unit 309 is a functional unit that stores conversion data (conversion table) in a table format indicating the correspondence between Lab values and CMYK values. This conversion table is a three-dimensional lookup table based on L values, a values, and b values of Lab values.

  The color conversion unit 310 is a functional unit that converts the Lab value of each pixel of the gamut mapping image data input from the gamut mapping unit 308 into CMYK values that can be output by the printer 400 using the color conversion table. .

  The image output unit 311 is a functional unit that outputs image data having CMYK values input from the color conversion unit 310 to the printer 400.

  Next, processing of the image processing apparatus 300 including the above-described functional units will be described based on the flowchart of FIG.

  First, in S101, when an image print command is input to the image processing apparatus 300 by the user's keyboard 200 operation, an image specified by the print command is transferred from the input image information storage unit 301 to the image color gamut analysis unit 303. Is input.

  Next, in S102, the image color gamut analysis unit 303 analyzes the color distribution used in the input image data input from the input image information storage unit 301, and calculates the input image color gamut information. The calculated input image color gamut information is stored in the input image information storage unit 301.

  Next, in S103, the similarity calculation unit 305 uses the input image color gamut information input from the input image information storage unit 301 and the previous color conversion color gamut information input from the processing history information storage unit 304 to determine the current color gamut information. The similarity of the color gamut between the input image and the previous input image is calculated.

  In step S <b> 104, the color conversion color gamut determination unit 306 selects and determines color conversion color gamut information based on the similarity calculated by the similarity calculation unit 305. That is, when the similarity is high, the previous color conversion color gamut information is selected, and when the similarity is low, the input image color gamut is selected. The determined color conversion color gamut information is stored in the processing history information storage unit 304.

  In step S105, the color gamut mapping unit 308 scales the monitor color gamut information input from the monitor color gamut information storage unit 302 with the color conversion color gamut information set by the color conversion color gamut determination unit 306. The temporary color gamut of the monitor is set. Based on the monitor temporary color gamut and the printer color gamut information input from the printer color gamut information storage unit 307, the color of the input image input from the input image information storage unit 301 is color gamut mapped. Details of the color gamut mapping process will be described later.

  Here, when the temporary color gamut of the monitor 100 is set using the previous color conversion color gamut information as a result of the process in S104, the same color reproduction (color gamut mapping) as the previous time is performed on the input image color. Is done. On the other hand, when the temporary color gamut of the monitor 100 is set using the input image color gamut information, color reproduction different from the previous time is performed, but an image with excellent gradation is obtained with respect to the input image.

  Next, in S106, the color conversion unit 310 refers to the conversion table of the color conversion table storage unit 309, and the gamut mapping image data input from the gamut mapping unit 308 is received by the printer 400 by a known interpolation method. It is converted into CMYK image data that can be output.

  In step S107, the image output unit 311 transmits the image data input from the color conversion unit 310 to the printer 400, and the printer 400 prints out the image data.

  Next, details of the color gamut mapping processing in the color gamut mapping unit 308 will be described with reference to FIG. FIG. 7 is a process explanatory diagram of the color gamut mapping unit 308, and FIG. 8 is a flowchart showing the process of the color gamut mapping unit 308.

  First, in S 111, the monitor gamut 601 input from the monitor gamut information storage unit 302 in the gamut mapping unit 308 is the color conversion gamut information (scaling coefficient) input from the color conversion gamut determination unit 306. The temporary monitor color gamut 701 is calculated by scaling. FIG. 7 shows a case where the color conversion color gamut information is 0.8. Here, the temporary monitor color gamut 701 is a color gamut similar to the monitor color gamut 601 as a point obtained by multiplying the maximum color saturation point 601a of the monitor color gamut by 0.8.

  In step S112, a mapping concentration point 704 is calculated using the printer color gamut information input from the printer color gamut information storage unit 307. A mapping concentration point 704 indicates a direction in which the input color 705 is mapped, and has the same lightness as the maximum saturation point 702a of the printer color gamut 702 and has no saturation.

  In step S <b> 113, the input color 705 moves on the straight line connecting the input color 705 and the mapping concentration point 704 toward the mapping concentration point 704, and is mapped to the mapping color 706 in the printer color gamut 702. Since the color gamut mapping is performed by proportionally allocating the temporary monitor color gamut 701 to the printer color gamut 702, when the size of the temporary monitor color gamut 701 changes, the result of the color gamut mapping also changes.

  Next, in S114, it is determined whether or not the mapping color 706 exists in the printer color gamut 702. If the mapping color 706 exists in the printer color gamut 702, the color gamut mapping processing is terminated, and the next The gamut mapping process for the input pixel is started, and the above-described gamut mapping process is repeated for all the pixels of the input image.

If the mapping color 706 exists outside the printer color gamut 702, a clipping process is executed in step S115 to replace the mapping color 706 outside the printer color gamut 702 with a color outside the printer color gamut 702. After the clipping process is completed, the color gamut mapping process for the next input pixel is started, and the above color gamut mapping process is repeated for all the pixels of the input image.
If the similarity described above is greater than 1.0, the mapping color 706 may not fall within the printer color gamut 702.

  As described above, according to the first embodiment, the same color reproduction can be performed for the same input color by setting the same color conversion color gamut for images having similar reproduction color gamuts of the input image data. The inconvenience of being reproduced with different colors for the same input color can be solved.

FIG. 9 is a block diagram illustrating a schematic configuration of the image processing apparatus according to the second embodiment.
As in the first embodiment, the image processing apparatus 500 according to the present embodiment includes a CPU 32, an input / output I / F 31, a program ROM 33, a RAM 34, an HDD 35, and the like. The input / output I / F 31 includes a monitor 100 and a keyboard as input devices. 200 is connected, and a printer 400 is connected as an output device.

FIG. 10 is a functional block diagram of an image processing apparatus 500 according to the second embodiment.
The image processing apparatus 500 of this embodiment includes an input image information storage unit 301, a monitor color gamut information storage unit 302, an image color gamut analysis unit 303, a processing history information storage unit 304, a printer color gamut information storage unit 307, a color gamut mapping. Unit 501, color gamut mapping image information storage unit 502 (data storage unit), difference image generation unit 503, color conversion table storage unit 309, color conversion unit 310, image output unit 311, and the like, as described above The CPU 32 is a functional unit realized by executing an image processing program developed on the RAM 34.
Of the above configuration, the input image information storage unit 301, the monitor color gamut information storage unit 302, the image color gamut analysis unit 303, the processing history information storage unit 304, the printer color gamut information storage unit 307, and the color conversion table storage unit 309. Since the functional units of the color conversion unit 310 and the image output unit 311 are the same as those in the first embodiment, the same reference numerals are given and description thereof is omitted.

The gamut mapping unit 501 calculates temporary monitor gamut information from the input image gamut information input from the input image information storage unit 301 and the monitor gamut information input from the monitor gamut information storage unit 302. Using the temporary monitor color gamut information and the printer color gamut information input from the printer color gamut information storage unit 307, the color of the input image data input from the input image information storage unit 301 is changed within the color gamut of the printer 400. This is a functional unit that generates reproduced (mapped) color gamut image data (second color gamut image data).
The temporary monitor color gamut information is calculated from the previous color conversion color gamut information input from the processing history information storage unit 304 and the monitor color gamut information input from the monitor color gamut information storage unit 302, and the temporary monitor gamut information is calculated. Using the color gamut information and the printer color gamut information input from the printer color gamut information storage unit 307, the color gamut mapping image data (first color gamut mapping) in which the color of the input image data is reproduced in the color gamut of the printer 400. It is also a functional unit that generates (image data).

  The color gamut mapping image information storage unit 502 includes the first color gamut mapping image data and the second color gamut mapping image data generated by the color gamut mapping unit 501, and the previous color conversion color gamut used for the color gamut mapping. It is a functional unit that stores information.

The difference image generation unit 503 is a functional unit that generates a difference image between the first gamut mapping image data and the second gamut mapping image data input from the gamut mapping image information storage unit 502.
This difference image is generated by calculating the color difference for each pixel of the first color gamut mapping image data and the second color gamut mapping image data. Pixels having no color difference are white and the color difference is large. This is an image shown in so-called gray scale, in which the pixels become black.

  Next, the processing of the image processing apparatus 500 including the above functional units will be described based on the flowchart of FIG.

  First, in step S <b> 201, when a user inputs an image print command to the image processing apparatus 500 by operating the keyboard 200, an image specified by the print command is transferred from the input image information storage unit 301 to the image color gamut analysis unit 303. Entered.

  In step S <b> 202, the image color gamut analysis unit 303 analyzes the color distribution used in the input image data input from the input image information storage unit 301 and calculates input image color gamut information. The calculated input image color gamut information is stored in the input image information storage unit 301.

  In step S203, the color gamut mapping unit 501 scales the monitor color gamut information input from the monitor color gamut information storage unit 302 with the input image color gamut information input from the input image information storage unit 301. A temporary color gamut of the monitor is set, and the color of the input image input from the input image information storage unit 301 is a color based on the monitor temporary color gamut and the printer color gamut information input from the printer color gamut information storage unit 307. By performing the gamut mapping, second color gamut mapping image data is generated.

  In step S204, the color gamut mapping unit 501 scales the monitor color gamut information input from the monitor color gamut information storage unit 302 with the previous color conversion color gamut information input from the processing history information storage unit 304. The temporary color gamut of the monitor is set, and the color of the input image is color gamut mapped based on the monitor temporary color gamut and the printer color gamut information input from the printer color gamut information storage unit 307. Color gamut image data is generated.

  Next, in S205, the difference image generation unit 503 generates a difference image between the second color gamut mapping image data generated in S203 and the first color gamut mapping image data generated in S204.

  Next, in S206, the second color gamut mapping image based on the second color gamut mapping image data generated in S203, the first color gamut mapping image based on the first color gamut mapping image data generated in S204, and in S205. The generated difference images are displayed on the monitor 100, respectively.

  Next, in S207, the user refers to the difference image displayed on the monitor 100, and the preferred color gamut mapping image to be output from the gradation of the first color gamut mapping image and the second color gamut mapping image. And the selected image is designated by the keyboard 200 operation to the image processing apparatus 500. The color gamut mapping image data designated by the user is input from the color gamut mapping image information storage unit 502 to the color conversion unit 310. At the same time, the color conversion color gamut information used when generating the selected color gamut mapping image data is stored in the processing history information storage unit 304.

  In step S <b> 208, the color conversion unit 310 refers to the color conversion table in the color conversion table storage unit 309, and the user-specified color gamut mapping image data input from the color gamut mapping image information storage unit 502 is transferred to the printer 400. Is converted into CMYK image data that can be output.

  In step S209, the image output unit 311 transmits the image data input from the color conversion unit 310 to the printer 400, and the printer 400 prints out the image data.

  As described above, according to the second embodiment, the first color gamut mapped image in which the same color reproduction as the previous color gamut mapping process is performed on the input image is different from the previous color reproduction, but the gradation property is optimum for the input image. By displaying the second color gamut mapping image that has undergone conversion and the difference image of these color gamut mapping images, the user can check the gradation of the difference image and each color gamut mapping image, as desired by the user. A preferred color gamut mapping image can be selected and printed out.

  In this embodiment, a monitor is used as an input device and a printer is used as an output device. However, the present invention can also be applied to an apparatus having an input / output device such as a copier.

1 is a block diagram illustrating a configuration of an image processing apparatus according to a first embodiment. 1 is a functional block diagram of an image processing apparatus according to Embodiment 1. FIG. It is a figure which shows the color gamut information example of a monitor. 3 is a diagram illustrating an example of color gamut information of a printer. FIG. It is processing explanatory drawing of an image color gamut analysis part. 3 is a flowchart illustrating processing of the image processing apparatus according to the first embodiment. It is processing explanatory drawing of a color gamut mapping part. It is a flowchart which shows the process of a color gamut mapping part. FIG. 6 is a block diagram illustrating a configuration of an image processing apparatus according to a second embodiment. 6 is a functional block diagram of an image processing apparatus according to Embodiment 2. FIG. 10 is a flowchart illustrating processing of the image processing apparatus according to the second embodiment.

Explanation of symbols

100 Monitor (input device)
300, 500 Image processing device 304 Processing history information storage unit (first information storage unit)
303 Image color gamut analysis unit 301 Input image information storage unit (second information storage unit)
305 Similarity Calculation Unit 306 Color Conversion Color Gamut Determination Unit 308, 501 Color Gamut Mapping Unit 400 Printer (Output Device)
502 Color gamut mapping image information storage unit (data storage unit)
503 Difference image generation unit

Claims (4)

In an image processing apparatus for converting image data in an input color gamut in an input device into image data in an output color gamut in an output device,
A first information storage unit for storing first image color gamut information relating to first image data input last time;
An image color gamut analyzing unit for calculating second image color gamut information relating to the second image data input this time;
A second information storage unit for storing the second image data and the second image color gamut information;
A similarity calculation unit for obtaining a similarity between the first image gamut information and the second image gamut information;
If the similarity is within a predetermined similarity range, the first image gamut information is set as the color gamut of the input device used for gamut mapping. If the similarity is outside the predetermined similarity range, the second color gamut information is set. A color conversion color gamut determining unit that sets the image color gamut information as the color gamut of the input device used for the color gamut mapping;
A color gamut obtained by mapping the color of the second image data into the color gamut of the output device based on the input color gamut used for the color gamut mapping set by the color conversion color gamut determining unit and the color gamut of the output device. An image processing apparatus comprising: a color gamut mapping unit that generates mapped image data.   The image processing apparatus according to claim 1, wherein the similarity is calculated based on a ratio between the first image color gamut information and the second image color gamut information. In an image processing apparatus for converting image data in an input color gamut in an input device into image data in an output color gamut in an output device,
A first information storage unit for storing first image color gamut information relating to first image data input last time;
An image color gamut analyzing unit for calculating second image color gamut information relating to the second image data input this time;
A second information storage unit for storing the second image data and the second image color gamut information;
Based on the first image color gamut information and the color gamut of the output device, first color gamut mapped image data in which the color of the second image data is mapped into the color gamut of the output device is generated, and the second A color gamut mapping unit that generates second color gamut mapping image data in which the color of the second image data is mapped into the color gamut of the output device based on the image color gamut information and the color gamut of the output device;
A data storage unit for storing the first color gamut mapping image data and the second color gamut mapping image data;
A difference image generation unit that generates a difference image between the first color gamut mapping image data and the second color gamut mapping image data;
The difference image is used as a criterion for selecting either the first color gamut mapping image data or the second color gamut mapping image data as output image data of the output device. .   The image processing apparatus according to claim 3, wherein the difference image is a grayscale image calculated from a color difference between pixels of the first color gamut mapping image data and the second color gamut mapping image data. .

Images