JP2008141724A - Image processing apparatus, image reproducing system, and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus, image reproducing system and image processing program capable of appropriately selecting a color characteristic to be used. <P>SOLUTION: A color characteristic deciding unit 100 judges as to whether or not a difference between an input color characteristic added to input image data and any reference color characteristic is within a predetermined threshold value and if within the threshold value, a color characteristic conversion coefficient for reference color characteristic within the threshold value is read from a reference color characteristic information storage unit 102 to a color characteristic conversion unit 104. If the difference is not within the threshold value, a color characteristic conversion coefficient generation unit 106 generates a color characteristic conversion coefficient on the basis of the input color characteristic and a color characteristic that can be reproduced by an image reproducing apparatus 12. A color characteristic conversion unit 104 uses the color characteristic conversion coefficient to perform processing for converting the input image data into the color characteristic that can be reproduced by the image reproducing apparatus 12. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Image data output from a digital camera or the like is often assumed to be reproduced based on a standard color space such as sRGB, but a color such as AdobeRGB having a wider color reproduction range than the standard color space. In some cases, space is assumed. For this reason, a configuration has been proposed in which color space identification information is added to image data in advance, and reproduction image data is generated based on the color space specified by the color space identification information.

For example, Patent Document 1 below discloses an image reproduction apparatus that switches generation processing of reproduction image data based on color space identification information.
No. 2004-77837

  However, there are many image data in which color space identification information is not added and only a color conversion coefficient (profile) created for each playback device is added. For this reason, the conventional technique has a problem that a color space to be used cannot be properly determined for image data to which color space identification information is not added.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an image processing apparatus, an image reproduction system, and an image processing program that can appropriately select a color characteristic to be used. .

  In order to achieve the above object, the invention of the image processing apparatus according to claim 1 is characterized in that a reference color characteristic information storage means for storing a reference color characteristic, an input color characteristic that is a color characteristic of input image data, and the reference color characteristic A color characteristic determination unit that determines whether the difference between the input image data and the difference is within a predetermined threshold; and when the difference is within the predetermined threshold, the image reproduction device can reproduce the input image data based on the reference color characteristic And a color characteristic conversion means for converting the color characteristics into various color characteristics.

  According to a second aspect of the present invention, in the first aspect of the present invention, when the difference between the input color characteristic and all the reference color characteristics stored in the reference color characteristic information storage means is larger than a predetermined threshold, A color characteristic conversion coefficient generating unit configured to generate a color characteristic conversion coefficient for converting the input image data into a color characteristic reproducible by the image reproduction apparatus based on the color characteristic and the color characteristic of the image reproduction apparatus; Features.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the threshold value is defined for each reference color characteristic stored in the reference color characteristic information storage unit.

  According to a fourth aspect of the present invention, in the first or second aspect of the invention, the threshold value is defined for chromaticity of a specific color signal in the input color characteristic and the reference color characteristic. To do.

  The invention according to claim 5 is the invention according to claim 1 or 2, wherein the threshold value is a chromaticity coordinate value of a reference white point of the input color characteristic and the standard color characteristic, a chromaticity coordinate value of a primary color, Any one of the color characteristic conversion coefficients is defined.

  According to a sixth aspect of the present invention, there is provided a reproduction gradation characteristic when the reproduction gradation characteristic of the input color characteristic and the reference color characteristic are different. It is further characterized by further comprising gradation characteristic correcting means for correcting.

  According to a seventh aspect of the invention, in the first aspect of the invention, the threshold value is a color difference or a hue difference between the input color characteristic and the reference color characteristic with respect to a specific color signal.

  According to an eighth aspect of the present invention, in the seventh aspect of the present invention, when the difference between the input color characteristic and all the reference color characteristics stored in the reference color characteristic information storage means is larger than a predetermined threshold, A color characteristic conversion coefficient generating unit configured to generate a color characteristic conversion coefficient for converting the input image data into a color characteristic reproducible by the image reproduction apparatus based on the color characteristic and the color characteristic of the image reproduction apparatus; Features.

  The invention according to claim 9 is the invention according to claim 7 or 8, wherein the threshold value is defined for each reference color characteristic stored in the reference color characteristic information storage means.

  According to a tenth aspect of the present invention, in the invention according to any one of the seventh to ninth aspects, the specific color signal is a signal based on a combination of saturation signals of color components constituting the input image data. It is characterized by.

  According to an eleventh aspect of the present invention, in the invention according to any one of the seventh to tenth aspects, the threshold value is set for each combination of saturation signals of color components constituting the input image data. It is characterized by.

  According to a twelfth aspect of the present invention, in the seventh to eleventh aspects of the invention, the gradation characteristics are corrected when the gradation characteristics of the primary color are different between the input color characteristics and the reference color characteristics. It further comprises tone characteristic correction means.

  An invention of an image reproduction system according to a thirteenth aspect includes the image processing apparatus according to any one of the first to sixth aspects, and an image reproduction apparatus that reproduces image data converted by the image processing apparatus. It is characterized by.

  The invention of an image processing program according to claim 14 determines whether or not a difference between an input color characteristic which is a color characteristic of input image data and a reference color characteristic stored in advance is within a predetermined threshold, and the difference is When it is within a predetermined threshold, the computer is caused to perform processing for converting the input image data into color characteristics that can be reproduced by the image reproduction device based on the reference color characteristics.

  According to the present invention, it is possible to provide an image processing apparatus, an image reproduction system, and an image processing program that can appropriately select a color characteristic to be used.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  FIG. 1 shows a functional block diagram of an embodiment of an image reproduction system according to the present invention. In FIG. 1, the image reproduction system includes an image processing device 10 and an image reproduction device 12. The image processing apparatus 10 selects appropriate color characteristics for image data acquired from an image data generation apparatus such as a digital camera, and generates reproduction image data. The image reproduction device 12 includes a printing device, an image display device, and the like, and reproduces and outputs the reproduction image data acquired from the image processing device 10.

  The image processing apparatus 10 includes a color characteristic determination unit 100, a reference color characteristic information storage unit 102, a color characteristic conversion unit 104, a color characteristic conversion coefficient generation unit 106, and a gradation characteristic correction unit 108.

  The color characteristic determination unit 100 is realized including a central processing unit (CPU) and a program for controlling the processing operation of the CPU, and whether or not a specific color characteristic (input color characteristic) is added to the input image data. And whether the input color characteristic matches the reference color characteristic by comparing the input color characteristic with a reference color characteristic stored in a reference color characteristic information storage unit 102 described later. Determine. Here, the color characteristic is a characteristic value of a color space designated when generating image data. Further, the color characteristic determination unit 100 also determines whether or not the reproduction gradation characteristic of the input image data is different from the reproduction gradation characteristic of the reference color characteristic.

  The reference color characteristic information storage unit 102 is realized by a read-only memory (read-only storage device ROM), a magnetic storage device such as a hard disk device, or other computer-readable storage device, and is a general storage device such as sRGB, AdobeRGB, or CMYK. Information on the color space is stored as reference color characteristic information.

  The color characteristic conversion unit 104 is realized including a CPU and a program for controlling processing operations of the CPU, and converts input image data into color characteristics that can be reproduced by the image reproduction device 12.

  The color characteristic conversion coefficient generation unit 106 is realized including a CPU and a program for controlling the processing operation of the CPU, and the input color characteristic does not match any of the reference color characteristics stored in the reference color characteristic information storage unit 102 In addition, a color characteristic conversion coefficient for converting the input image data into color characteristics reproducible by the image reproduction device 12 is generated. The color characteristic conversion coefficient is generated based on the input color characteristic and the color characteristic reproducible by the image reproduction device 12, and is used by the color characteristic conversion unit 104 to convert the input image data.

  The gradation characteristic correction unit 108 is realized including a CPU and a program for controlling the processing operation of the CPU, and corrects the reproduction gradation characteristic when the reproduction gradation characteristic differs between the input color characteristic and the reference color characteristic. .

  FIG. 2 is an explanatory diagram showing an example of a method by which the color characteristic determining unit 100 determines the input color characteristic. In FIG. 2, white squares (□) are primary color chromaticity points in the AdobeRGB color space as reference color characteristics, and black circles (●) are primary color chromaticity points in the sRGB color space. Here, the primary color means red (R) green (G) blue (B). These pieces of information are stored in the reference color characteristic information storage unit 102.

  The white triangle (Δ) is the primary color chromaticity point of the image display apparatus A that was displayed before the input image data was input to the image processing apparatus 10, and the asterisk (*) is the primary color of the image display apparatus B. A chromaticity point, and a white circle (◯) is a primary color chromaticity point of the image display device C and represents an input color characteristic. In this example, the case where there are three image display devices displayed before the input image data is input to the image processing device 10 is shown, but the number is not limited to three. Further, it is assumed that the color characteristics (input color characteristics) of each image display device are added to the input image data as primary color chromaticity points.

The color characteristic determination unit 100 compares the reference color characteristics shown in FIG. 2 with the primary color chromaticity points of the image display device, and determines the difference. In the example of FIG. 2, the respective differences are displayed as the coincidence or disagreement of the positions of the primary color chromaticity points, but the color characteristic determination unit 100 grasps this difference as a numerical difference representing chromaticity. The difference in numerical values representing the chromaticity is a difference in distance on the xy chromaticity diagram shown in FIG. Tables 1 (a) and 1 (b) show numerical values of these differences. Table 1 (a) shows numerical values of differences between the primary color chromaticity points in the sRGB color space and the primary color chromaticity points of the image display apparatuses A, B, and C. Table 1 (b) shows the primary colors in the AdobeRGB color space. It is a numerical value of the difference between the degree point and the primary color chromaticity point of the image display devices A, B, and C.

  The color characteristic determining unit 100 determines whether or not the numerical value of each difference is within a predetermined threshold. When the numerical value of the difference is within a predetermined threshold, it is determined that the respective primary color chromaticity points are matched, and when all the primary color chromaticity points are matched, the reference color characteristics and the input displayed on the image display device are displayed. It is determined that the input color characteristics of the image data match. In the examples of Tables 1 (a) and 1 (b), for example, when the threshold value is set to 0.03, the color characteristics of the image display apparatus A match the sRGB color space and do not match the AdobeRGB color space. In addition, the color characteristics of the image display apparatus B match the AdobeRGB color space, and do not match the sRGB color space. Further, the color characteristics of the image display device C do not match any color space.

The above determination is performed for each of the three primary color chromaticity points. However, the determination may be made based on the average value of the differences in the three primary color chromaticity points, and any specific chromaticity (for example, only G) is determined. May be. Alternatively, the determination may be made based on the chromaticity coordinate value of the reference white point, the chromaticity coordinate value of the primary color, a color characteristic conversion coefficient to a specific color space such as L ^* a ^* b ^* , and the like. In these cases, determination is performed by setting an appropriate threshold value.

FIG. 3 shows an explanatory diagram of another example of a method by which the color characteristic determining unit 100 determines the input color characteristic. FIG. 3 is an a ^* b ^* plane in the L ^* a ^* b ^* color space, and shows three examples (a), (b), and (c) of typical reference color characteristics of CMYK. In addition, (a) represents the area | region enclosed with the dashed-dotted line, (b) represents the area | region enclosed with the continuous line, (c) represents the area | region enclosed with the dashed-two dotted line. These reference color characteristics indicate a color reproduction range that is reproduced in the CMYK color space defined by, for example, JapanColor2001. In FIG. 3, the horizontal axis represents the a ^* axis and the vertical axis represents the b ^* axis. Each vertex of the area indicated by a hexagon is a specific color signal represented by a saturation signal or a combination thereof, and the upper vertex in the figure is Y (yellow), and R (red), M ( Magenta), B (blue), C (cyan), and G (green). Here, C, M, and Y are primary colors, R (Y and M are mixed at 100%), G (Y and C are mixed at 100%), and B (C and M are mixed at 100%). Is the secondary color.

For example, when the input color characteristics indicated by the dotted line α and the broken line β are designated as the input color characteristics of the input image data, the color characteristic determination unit 100 determines the difference between each vertex of the input color characteristics and each vertex of the reference color characteristics. It is determined whether it is within a predetermined threshold. In this case, it is preferable to determine whether or not an angle formed by a straight line connecting the origin and each vertex, that is, the intersection of the a ^* axis and b ^* axis, that is, the hue difference is within the threshold value range. Note that, instead of the hue difference, the above determination may be made based on a color difference that is a distance in the L ^* a ^* b ^* color space in which the L axis (luminance component) is added to the a ^* axis b ^* axis in FIG. The threshold value is set for each of the specific color signals corresponding to the six vertices. Further, the determination using this threshold value may be performed for all of the specific color signals corresponding to the six vertices, or may be performed for a part.

  Since the dotted line α is close to the reference color characteristic (c), the color characteristic conversion unit 104 is input using a color conversion coefficient stored in the reference color characteristic information storage unit 102 in advance, assuming (c). The obtained image data is converted into color characteristics that can be reproduced by the image reproduction device 12. Also, since the broken line β has a large difference from any of the reference color characteristics (a), (b), and (c), the color characteristic conversion coefficient generation unit 106 generates a color conversion coefficient suitable for the characteristic of the broken line β. The color characteristic conversion unit 104 converts the input image data into color characteristics that can be reproduced by the image reproduction device 12 using the generated coefficients.

  Note that the color components to be determined are not limited to the six colors shown in FIG. 3 and may be any color represented by a combination of saturation signals. For example, a tertiary color or a quaternary color may be used. Good.

  FIG. 4 shows a flow of an operation example of the image processing apparatus 10 according to the present embodiment. In FIG. 4, the color characteristic determination unit 100 determines whether or not an input color characteristic is added to the input image data (S1).

  In S1, when the input color characteristic is not added to the input image data, a predetermined reference color characteristic, for example, a color characteristic conversion coefficient for the sRGB color space is transferred from the reference color characteristic information storage unit 102 to the color characteristic conversion unit 104. Read (S2). This color characteristic conversion coefficient is a coefficient for converting image data in the sRGB color space into a color characteristic that can be reproduced by the image reproduction device 12, for example, a CMYK color space. Therefore, the input image data is converted by the color characteristic conversion unit 104 as having a predetermined reference color characteristic such as an sRGB color space.

  In S1, when the input color characteristic is added to the input image data, the color characteristic determination unit 100 uses either the input color characteristic of the input image data or any one of the input image data by the method described in FIG. It is determined whether the difference from the reference color characteristic is within a predetermined threshold (S3).

  If the difference is within the threshold value in S3, the color characteristic conversion coefficient for the reference color characteristic that falls within the threshold value is read from the reference color characteristic information storage unit 102 to the color characteristic conversion unit 104 (S4).

On the other hand, if the difference is not within the threshold value in S3, the other reference color characteristics are compared with the input color characteristics. As a result, after comparison with all the reference color characteristics, if the difference from any of the reference color characteristics is not within the threshold value (S5), the color characteristic conversion coefficient generation unit 106 reproduces the input color characteristics and the image reproduction device 12. Based on the possible color characteristics, color characteristic conversion coefficients suitable for the input color characteristics are generated (S6). The input color characteristic includes a color characteristic conversion coefficient between a specific color space such as L ^* a ^* b ^* , which does not depend on the normal image reproduction device 12. Also, color characteristic conversion coefficients between color characteristics such as Adobe RGB, sRGB, and CMYK that can be reproduced by the image reproduction device 12 and a specific color space such as the L ^* a ^* b ^* color space are known in advance. Therefore, the color characteristic conversion coefficient generation unit 106 temporarily converts the input color characteristics into a device-independent color space such as an L ^* a ^* b ^* color space, and the image reproduction device 12 uses the device-independent color space. A color characteristic conversion coefficient for conversion to a color space is generated.

  Next, the color characteristic conversion unit 104 executes processing for converting the input image data into color characteristics that can be reproduced by the image reproduction device 12 using the color characteristic conversion coefficient obtained in S2, S4, or S6 (S7). ).

  Through the above steps, the color characteristic to be used can be appropriately selected according to the input image data.

  FIGS. 5A and 5B are explanatory diagrams of a method for correcting the reproduction gradation characteristic added to the input image data. In this example, the color characteristic determination unit 100 determines that the difference between the primary color chromaticity point of the image display apparatus on which the input image data is displayed and the primary color chromaticity point of any reference color characteristic is within a predetermined threshold. Applies when judged.

  In order to reproduce intermediate colors between the primary colors (RGB), the input image data is added with the reproduction gradation characteristics of the image display device that was displayed before the input image data was input to the image processing device 10. ing. When the reproduction gradation characteristic of the input image data is different from the reproduction gradation characteristic of the reference color characteristic, appropriate image data cannot be output to the image reproduction device 12. Therefore, the gradation characteristic correction unit 108 corrects the reproduction gradation characteristic of the input image data so as to match the reproduction gradation characteristic of the reference color characteristic determined to be coincident by the color characteristic determination unit 100.

  In FIG. 5A, the reproduction gradation characteristic of the image display apparatus that displayed the input image data is indicated by a solid line, and the reproduction gradation characteristic of the sRGB color space, which is a reference color characteristic, is indicated by a broken line. In the example shown in FIG. 5A, there is a difference between the reproduction gradation characteristics of the input image data and the reproduction gradation characteristics of the sRGB color space. This shift is due to the fact that the reproduction gradation characteristic curve is defined as 2.2 in terms of gamma value in the sRGB color space, whereas another gamma value is defined in the image display device displaying the input image data. It occurs because of having been. Therefore, the gradation characteristic correction unit 108 generates a correction curve as shown in FIG. 5B from the relationship between the reproduction gradation characteristic of the input image data and the reproduction gradation characteristic of the sRGB color space, and generates the input image data. Correct by multiplying.

  FIGS. 6A and 6B are explanatory diagrams of another method for correcting the reproduction gradation characteristic added to the input image data. In this example, the CMYK color space is set as the input color characteristic of the input image data. This example is also applied when the color characteristic determination unit 100 determines that the difference between the input color characteristic and any one of the reference color characteristics is within a predetermined threshold.

  In FIG. 6A, the reproduction gradation characteristic of the input image data is indicated by a solid line, and the reproduction gradation characteristic of the reference color characteristic (for example, the CMYK color space defined by JapanColor2001) is indicated by a broken line. In this example, the reproduction gradation characteristics of the primary color (for example, Y) are used. In the example shown in FIG. 6A, there is a difference between the reproduction gradation characteristic of the input image data and the reproduction gradation characteristic of the reference color characteristic. Therefore, the gradation characteristic correcting unit 108 generates a correction curve as shown in FIG. 6B from the relationship between the reproduction gradation characteristic of the input image data and the reproduction gradation characteristic of the reference color characteristic, and generates the input image data. Correct by multiplying.

  FIG. 7 shows a flow of another operation example of the image processing apparatus 10 according to the present embodiment. Here, steps S11 to S17 in FIG. 7 are the same as steps S1 to S7 in FIG.

  In FIG. 7, when the difference between the input color characteristic of the input image data and one of the reference color characteristics is within a predetermined threshold (S13), the color characteristic determination unit 100 determines the reproduction gradation characteristic of the input image data as It is determined whether or not the reproduction tone characteristics of the reference color characteristics (for example, sRGB color space, CMYK color space defined by JapanColor2001) are different (S18). In S18, when the two reproduction gradation characteristics are different, the gradation characteristic correction unit 108 uses the method described in FIGS. 5A and 5B or FIGS. 6A and 6B to convert the input image data. The reproduction gradation characteristic is corrected (S19). After correcting the reproduction tone characteristics of the input image data, the color characteristic conversion unit 104 converts the input image data into color characteristics that can be reproduced by the image reproduction device 12 using the color characteristic conversion coefficient obtained in S14. Is executed (S17). If the two reproduction gradation characteristics are not different in S18, the reproduction gradation characteristics are not corrected in S19.

  As described above, the image data in which the reproduction gradation characteristic of the input image data is appropriately corrected can be output to the image reproduction device 12.

It is a functional block diagram of one embodiment of an image reproduction system concerning the present invention. It is explanatory drawing of the example of the method of discriminating an input color characteristic. It is explanatory drawing of the other example of the method of discriminating an input color characteristic. It is a flowchart of the operation example of the image processing apparatus concerning this invention. It is explanatory drawing of the method of correct | amending the reproduction | regeneration gradation characteristic added to the input image data. It is explanatory drawing of the other method of correct | amending the reproduction | regeneration gradation characteristics added to the input image data. It is a flowchart of the other operation example of the image processing apparatus concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 image processing apparatus, 12 image reproduction apparatus, 100 color characteristic discrimination | determination part, 102 reference | standard color characteristic information storage part, 104 color characteristic conversion part, 106 color characteristic conversion coefficient production | generation part, 108 gradation characteristic correction part.

Claims (14)

Reference color characteristic information storage means for storing reference color characteristics;
Color characteristic determination means for determining whether a difference between an input color characteristic that is a color characteristic of input image data and the reference color characteristic is within a predetermined threshold;
Color characteristic conversion means for converting the input image data into color characteristics that can be reproduced by the image reproduction device based on the reference color characteristics when the difference is within a predetermined threshold;
An image processing apparatus comprising:   2. The image processing apparatus according to claim 1, wherein when the difference between the input color characteristic and all the reference color characteristics stored in the reference color characteristic information storage unit is larger than a predetermined threshold, the input color characteristic and the image reproduction apparatus. An image processing apparatus comprising color characteristic conversion coefficient generation means for generating a color characteristic conversion coefficient for converting the input image data into a color characteristic reproducible by the image reproduction apparatus based on the color characteristics of the image .   3. The image processing apparatus according to claim 1, wherein the threshold value is defined for each reference color characteristic stored by the reference color characteristic information storage unit.   3. The image processing apparatus according to claim 1, wherein the threshold value is defined for chromaticity of a specific color signal in the input color characteristic and the reference color characteristic.   3. The image processing apparatus according to claim 1, wherein the threshold value is any one of a chromaticity coordinate value of a reference white point, a chromaticity coordinate value of a primary color, and a color characteristic conversion coefficient of the input color characteristic and the standard color characteristic. An image processing apparatus characterized by the above.   The image processing apparatus according to claim 1, wherein a gradation characteristic correction that corrects a reproduction gradation characteristic when the reproduction gradation characteristic differs between the input color characteristic and the reference color characteristic. An image processing apparatus further comprising means.   The image processing apparatus according to claim 1, wherein the threshold is a color difference or a hue difference between the input color characteristic and the reference color characteristic with respect to a specific color signal.   The image processing apparatus according to claim 7, wherein the difference between the input color characteristic and all the reference color characteristics stored in the reference color characteristic information storage unit is greater than a predetermined threshold value. An image processing apparatus comprising color characteristic conversion coefficient generation means for generating a color characteristic conversion coefficient for converting the input image data into a color characteristic reproducible by the image reproduction apparatus based on the color characteristics of the image .   9. The image processing apparatus according to claim 7, wherein the threshold value is defined for each reference color characteristic stored in the reference color characteristic information storage unit.   10. The image processing device according to claim 7, wherein the specific color signal is a signal based on a combination of saturation signals of color components constituting input image data. 11. apparatus.   11. The image processing device according to claim 7, wherein the threshold value is set for each combination of saturation signals of color components constituting the input image data. apparatus.   The image processing apparatus according to any one of claims 7 to 11, further comprising a gradation characteristic correcting unit that corrects a gradation characteristic when a gradation characteristic of a primary color is different between the input color characteristic and the reference color characteristic. An image processing apparatus comprising:   An image reproduction system comprising: the image processing apparatus according to any one of claims 1 to 6; and an image reproduction apparatus that reproduces image data converted by the image processing apparatus. Determining whether a difference between an input color characteristic which is a color characteristic of the input image data and a reference color characteristic stored in advance is within a predetermined threshold;
An image processing program for causing a computer to execute a process of converting the input image data into a color characteristic that can be reproduced by an image reproduction device based on the reference color characteristic when the difference is within a predetermined threshold value. .

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