JP2007214970A - Color adjustment device and method, color adjustment program and memory medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color adjustment device and a color adjustment method for bringing object color close to target color and attaining the reproduction of superior color balance of the whole image when the object color to be adjusted is adjusted close to the target color. <P>SOLUTION: In a partial color space including an object color as an adjustment object and a target color as an adjustment target in a color space for showing color image, a selective color adjustment unit 11 performs the regulation so that there may be no gray level inverse in the partial color space including the object color and the target color while it goes to the target color from the object color. In a color distribution analysis unit 12, a selective color adjustment image after partial color adjustment from the object color to the target color is analyzed and a histogram is generated. In a gray level transformation curve formation unit 13, a gray level transformation curve for bringing the histogram of the selective color adjustment image close to the target histogram is generated. By using the gray level transformation curve, the color adjustment for the whole selective color adjustment image is carried out in the whole color adjustment unit 14. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color adjustment technique for adjusting the color of a color image.

  A technique for adjusting a specific color in a color image is often applied to a color called a memory color such as a human skin for a natural image, a sky in a landscape, or a green of a plant. As described above, when the target color to be adjusted is adjusted toward the target color to be the adjustment target, it is important that the other colors are not affected. However, even if only the target color can be adjusted, the entire image may feel unnatural. For example, even when the local adjustment is performed so that the color of the human skin becomes brighter, in the case of an image that is dark as a whole, only the skin of the person is brightened, and the entire image becomes unbalanced. Although it is important to adjust the target color toward the target color, as a result, the preference for the entire image must be taken into consideration, so the target color is adjusted in consideration of the overall color balance. It is necessary to do.

  As a conventional method for performing adjustment from the target color toward the target color, for example, there is a color adjustment method described in Patent Document 1. In this color adjustment method, a partial color space including the target color to be adjusted and the target color to be adjusted is set in the color space representing the color image, and color adjustment is performed only in the partial color space. It can be carried out. By moving the point so that the target color (target point) becomes the target color (target point) and without reversal, the specific color can be adjusted without affecting other colors. .

  According to the color adjustment method described in Patent Document 1, if the range of the partial color space is set to be slightly wider, it is possible to perform adjustment that is natural for the entire image. However, it is not possible to automatically set a range after adaptively determining a color distribution for various images. Further, since the color adjustment range centering on the target color is set, the color distribution of the entire image is not taken into consideration. For this reason, there has been a problem in that it is impossible to perform color adjustment that balances the adjustment of the target color and the adjustment of the entire image.

JP 2004-112694 A

  The present invention has been made in view of the above-described circumstances. When the target color to be adjusted is adjusted toward the target color to be adjusted, the target color is brought close to the target color and the entire image is An object is to provide a color adjustment apparatus and a color adjustment method capable of performing color adjustment with good color balance reproduction, a color adjustment program for performing such color adjustment, and a storage medium storing the color adjustment program It is.

  The present invention relates to a color adjustment apparatus and a color adjustment method for adjusting the color of a color image, and performs local color adjustment from a target color to be adjusted toward an adjustment target color, and performs the local color adjustment. The present invention is characterized in that color adjustment is performed on the entire color image. More specifically, first, a selective color from the target color toward the target color in the partial color space including the target color to be adjusted in the color space representing the color image and the target color to be adjusted. Make adjustments. Then, color adjustment is performed on the entire selective color adjustment image in accordance with the color distribution of the selective color adjustment image which is a color image after performing selective color adjustment.

  The color adjustment for the entire selective color adjustment image may be performed so that the color distribution of the selective color adjustment image, for example, the histogram for the pixel values of the selective color adjustment image, approaches the target color distribution. In addition, when performing overall color adjustment using such a histogram, it is preferable to use a gradation conversion curve such that the histogram for the pixel value of the selective color adjustment image approaches the target histogram. The gradation conversion curve at this time is a curve that adjusts the color balance for the entire selective color adjustment image, or depends on the importance of adjustment for the target color to be adjusted, or the importance of adjustment for the entire color image Control. Furthermore, the gradation conversion curve may be controlled according to the scene represented by the color image, or at least one of the target color and the target color.

  The present invention is also a color adjustment program, characterized by causing a computer to execute color adjustment processing for adjusting the color of a color image as described above. The computer-readable storage medium stores the above-described color adjustment program.

  According to the present invention, when the target color to be adjusted is adjusted toward the target color to be adjusted, the target color is brought close to the target color and the color balance of the entire image is reproduced well. There is an effect that adjustment can be performed.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, 11 is a selective color adjustment unit, 12 is a color distribution analysis unit, 13 is a gradation conversion curve generation unit, and 14 is an overall color adjustment unit.

  The selective color adjustment unit 11 performs gradation in a partial color space including the target color and the target color from the target color to be adjusted toward the adjustment target color in the color space representing the given color image. Local color adjustment is performed so that reversal does not occur. This local color adjustment can be performed by applying the color adjustment method described in Patent Document 1, for example. The color image after the local color adjustment by the selective color adjustment unit 11 is set as a selective color adjustment image.

  The color distribution analysis unit 12 analyzes the color distribution of the selective color adjustment image. The color distribution can be represented by, for example, a histogram for pixel values of the selective color adjustment image.

  The gradation conversion curve generation unit 13 generates a gradation conversion curve such that the histogram obtained by the color distribution analysis unit 12 approaches the target histogram. At this time, a curve for adjusting the color balance with respect to the entire selective color adjustment image can be generated as the gradation conversion curve. Further, more optimal color adjustment can be performed by controlling the gradation conversion curve in accordance with the importance of the adjustment with respect to the target color to be adjusted or the importance of the adjustment with respect to the entire color image.

  The overall color adjustment unit 14 performs color adjustment on the entire selective color adjustment image using the gradation conversion curve generated by the gradation conversion curve generation unit 13. As described above, the gradation conversion curve generated by the gradation conversion curve generation unit 13 brings the color distribution (histogram) of the selective color adjustment image closer to the target color distribution (histogram). The selective color adjustment image is subjected to optimal color adjustment as a whole by the adjustment unit 14.

  An example of the operation in the first embodiment of the present invention will be briefly described. The color image to be processed is first subjected to local color adjustment in the selective color adjustment unit 11 to generate a selective color adjustment image. FIG. 2 is a conceptual diagram of local color adjustment in the selective color adjustment unit 11. The selective color adjustment unit 11 includes the target color and the target color from the target color to be adjusted toward the target color to be adjusted using, for example, the color adjustment method described in Patent Document 1. Performs adjustment without gradation reversal in the partial color space. As shown in FIG. 2, color adjustment is performed in a partial color space including the target color and the target color. In the figure, the outline of the partial color space is indicated by a bold line. The target color is converted to the target color, and at the same time, the surrounding colors are adjusted so that color inversion does not occur. Further, in order to prevent a color jump or the like inside or outside the partial color space, and to adjust the adjustment amount to 0 in the outline of the partial color space, the colors in the partial color space are indicated by arrows in the figure. Make adjustments.

  By such local color adjustment, it is possible to adjust a memory color such as a person's skin, a landscape sky, and a green plant without affecting other colors. Of course, the color to be adjusted is not limited to such a memory color, and any color may be used. Further, the local color adjustment method is not limited to the method described in Patent Document 1.

  Next, using the image adjusted by the selective color adjustment unit 11 as a selective color adjustment image, color adjustment is performed on the entire selective color adjustment image. FIG. 3 is an explanatory diagram of an example of color adjustment for the entire selective color adjustment image. In order to adjust the color of the entire selective color adjustment image, the color distribution analysis unit 12 first analyzes the color distribution of the entire image of the selective color adjustment image. The analysis result of the color distribution may be a histogram for the pixel values of the entire image, for example. In the example shown in FIG. 3A, the color image is assumed to be an image in the RGB color space, and a histogram is created for each color component.

  When the color distribution analysis unit 12 obtains an analysis result (here, a histogram) of the color distribution of the selective color adjustment image in this way, the tone conversion curve generation unit 13 uses the analysis result to obtain an appropriate color distribution. A gradation conversion curve that approaches is generated. An example of the generated gradation conversion curve is shown in FIG. Here, since the histogram is obtained for each of the R, G, and B color components, the gradation conversion curve is also generated for each of R, G, and B.

  Here, the appropriate color distribution may be, for example, a color distribution with a good color balance. The color balance represents a balance as a color distribution, such as white balance, brightness contrast, and saturation contrast. If there is an adjustment design guideline, a target color distribution may be set in advance. Here, a histogram as shown in FIG. 3C is set as a target of an appropriate color distribution, and the histogram of the selective color adjustment image shown in FIG. 3A becomes the target histogram shown in FIG. As described above, the gradation conversion curve generation unit 13 generates a gradation conversion curve.

  The overall color adjustment unit 14 performs gradation conversion on the entire selective color adjustment image using the gradation conversion curve generated by the gradation conversion curve generation unit 13. As a result, the image subjected to overall color adjustment (final adjustment image) becomes an image in which the target color is brought close to the target color and the color balance of the entire image is appropriately adjusted. By this overall color adjustment, the histogram of the selective color adjustment image shown in FIG. 3A becomes the final adjustment image that becomes a histogram as shown in FIG.

  The specific example shown in FIG. 3 is for a certain color image, and the histogram of the selective color adjustment image varies greatly depending on the color image to be processed and the result of local color adjustment. The key conversion curve will also change.

FIG. 3 shows an example using the RGB color space, but any color space such as YCbCr or L ^* a ^* b ^* can be used as long as it is a color space that represents an image. Good. Further, as an analysis result in the color distribution analysis unit 12, a histogram for each color component can be generated, for example, a three-dimensional histogram can be created, or an analysis result other than the histogram can be output.

  The gradation conversion curve generated by the gradation conversion curve generation unit 13 is controlled according to the state of the final adjustment image depending on the importance of the adjustment from the target color to the target color and the adjustment of the entire image. can do. For example, when priority is given to the adjustment of the entire image, the curve can be set to be stronger, and when priority is given to the adjustment from the target color to the target color, the curve can be set to be weaker. For example, in the case of the gradation conversion curve shown in FIG. 3B, the strength of the curve indicates a state in which adjustment is not performed when the input side and the output side are straight lines having the same value. Adjustment will be made strongly. Further, the output value is adjusted to be larger than the input value when it is separated from the upper left of the straight line, and the output value is adjusted to be smaller than the input value when it is separated from the lower right. Of course, as shown in FIG. 3B, the gradation conversion curve has various shapes, but it is necessary to increase monotonously so as not to cause color inversion.

  FIG. 4 is a block diagram showing a second embodiment of the present invention. In the figure, the same parts as those in FIG. In the second embodiment, for example, when it is desired to brighten the entire image or when it is desired to add sharpness, adjustment is performed according to the scene of the color image to be adjusted. As a configuration for this purpose, in this second embodiment, scene characteristics of a color image are input to the gradation conversion curve generation unit 13. The gradation conversion curve generation unit 13 generates a gradation conversion curve corresponding to the input scene feature and passes it to the overall color adjustment unit 14.

  FIG. 5 is an explanatory diagram of an example of a target histogram corresponding to a scene, and FIG. 6 is an explanatory diagram of an example of a scene of a color image. In the example shown in FIG. 5A, the histogram peak of each color component is on the larger value side. Therefore, an overall bright image is targeted. In the example shown in FIG. 5B, the histogram of each color component has two peaks having a larger value and a smaller value. As a result, it is possible to target an image having a bright portion and a dark portion.

  If the input scene feature is a dark image such as a cloudy image, the tone conversion curve generation unit 13 uses a target histogram as shown in FIG. A gradation conversion curve targeting a bright image is generated. Also, if the image has many edge portions such as a striped pattern, a tone conversion curve that targets a sharp image as a whole can be generated using a target histogram as shown in FIG. That's fine. For example, in the case of a scene including a person as shown in FIG. 6A, after adjusting the skin color and the like by the selective color adjustment unit 11, a target histogram as shown in FIG. What is necessary is just to adjust to the image which improved sharpness by using. For example, in the case of a landscape scene as shown in FIG. 6B, after the sky color, the sea color, etc. are adjusted by the selective color adjustment unit 11, the whole is shown in FIG. 5A. What is necessary is just to adjust to a bright image using such a target histogram. In this way, it is possible to generate a gradation conversion curve corresponding to the scene of the color image to be adjusted and perform overall adjustment.

  Note that the gradation conversion curve may be created in advance according to some target histograms, and the gradation conversion curve may be selected according to the input scene specification. For example, in the case of a scene including a person as shown in FIG. 6A, a gradation conversion curve that improves sharpness is selected to adjust a selective color adjustment image, and for example, as shown in FIG. 6B. In the case of such a landscape scene, a selective color adjustment image may be adjusted by selecting a gradation conversion curve for improving brightness.

  In the above description, the scene characteristics of the color image to be adjusted are given. However, the scene of the color image can be automatically determined. The scene may be determined by applying, for example, a known image recognition process or by using tag information such as an Exif image in a shooting mode such as a person mode or a landscape mode. Of course, the scene type can also be input manually.

  FIG. 7 is a block diagram showing a third embodiment of the present invention. In the figure, the same parts as those in FIG. In the third embodiment, an example in which the gradation conversion curve is controlled according to the target color or the target color is shown. As a configuration for this purpose, in the third embodiment, the target color and the target color used in the selective color adjustment unit 11 are also input to the gradation conversion curve generation unit 13. The gradation conversion curve generation unit 13 generates a gradation conversion curve corresponding to the input target color and target color and passes it to the overall color adjustment unit 14.

  FIG. 8 is a flowchart showing an example of an operation using the target color of the gradation conversion curve generation unit 13 according to the third embodiment of the present invention. Here, an example is shown in which corresponding gradation conversion curves are generated for blue such as sky and skin color such as human skin. In S21, the target color used in the selective color adjustment unit 11 is determined. If the target color is blue, a gradation conversion curve for a landscape image is generated in S22. If the target color is skin color, a gradation conversion curve for a human image is generated in S23. If neither of these is true, a gradation conversion curve for a general image is generated in S24. The generated gradation conversion curve is transferred to the overall color adjustment unit 14 and the overall color adjustment is performed on the selective color adjustment image.

  Here, an example is shown in which corresponding gradation conversion curves are generated for blue and flesh color, but the present invention is not limited to this, and it can be configured to generate gradation conversion curves corresponding to various target colors. Similarly, a tone conversion curve corresponding to each target color can be generated even if the target color is used instead of the target color.

  Furthermore, since the influence on the histogram of the entire image differs depending on the distance between the target color and the target color, a gradation conversion curve corresponding to the distance between the target color and the target color can be generated. FIG. 9 is an explanatory diagram of an example of the distance between the target color and the target color. As described with reference to FIG. 2, the selective color adjustment unit 11 uses, for example, a color adjustment method described in Patent Document 1 to move from a target color to be adjusted to a target color to be an adjustment target. Then, adjustment is performed so that there is no gradation inversion in the partial color space including the target color and the target color. At this time, as shown in FIG. 9B, when the distance between the target color and the target color in the color space is short, even if the color is adjusted in the partial color space, the influence on the whole is small. As shown in FIG. 9A, if the distance between the target color and the target color in the color space is long, there is a high possibility that color deviation occurs in the entire image. For example, when a histogram of a selective color adjustment image is created, the shape of the histogram changes due to local color adjustment. If this change is adjusted largely, the influence on the histogram will increase.

  As described above, since the influence on the entire image varies depending on the distance between the target color and the target color, the gradation conversion curve may be controlled according to the distance between the target color and the target color. For example, when the distance between the target color and the target color is small as shown in FIG. 9B, the curve is set to be weak, and the distance between the target color and the target color is set as shown in FIG. If it is large, the curve can be set stronger.

  In either case, several gradation conversion curves are generated in advance, and the corresponding gradation conversion curve is selected according to the target color or target color or the distance between the target color and the target color. You may comprise as follows.

  FIG. 10 is an explanatory diagram of an example of a computer program and a storage medium storing the computer program when the function of the color adjustment apparatus or the color adjustment method of the present invention is realized by the computer program. In the figure, 31 is a program, 32 is a computer, 41 is a magneto-optical disk, 42 is an optical disk, 43 is a magnetic disk, 44 is a memory, 51 is a magneto-optical disk apparatus, 52 is an optical disk apparatus, and 53 is a magnetic disk apparatus.

  Part or all of the functions of the units described in the above embodiments can be realized by a program 31 that can be executed by a computer. In that case, the program 31 and data used by the program (including data of the generated color conversion model) can be stored in a computer-readable storage medium. A storage medium is a signal format that causes a state of change in energy such as magnetism, light, electricity, etc. according to the description of a program to a reader provided in the hardware resources of a computer. Thus, the description content of the program can be transmitted to the reading device. For example, there are a magneto-optical disk 41, an optical disk 42 (including a CD and a DVD), a magnetic disk 43, a memory 44 (including an IC card and a memory card), and the like. Of course, these storage media are not limited to portable types.

  By storing the program 31 in these storage media and mounting these storage media in, for example, the magneto-optical disk device 51, the optical disk device 52, the magnetic disk device 53, or a memory slot or interface (not shown) of the computer 32, The computer can read the program 31 and execute the function of the image processing apparatus or the image processing method of the present invention. Alternatively, a storage medium may be attached to the computer 32 in advance, and the program 31 may be transferred to the computer 32 via a network, for example, and the program 31 may be stored and executed on the storage medium.

  Of course, some functions may be configured by hardware, or all may be configured by hardware. Alternatively, it may be configured as a program including the configuration of the color conversion apparatus of the present invention together with other configurations, and may be configured as one program together with a control program such as an image forming apparatus. Of course, in the case of application to other purposes, integration with a program for that purpose is also possible.

It is a block diagram which shows the 1st Embodiment of this invention. 5 is a conceptual diagram of local color adjustment in a selective color adjustment unit 11. FIG. It is explanatory drawing of an example of the color adjustment with respect to the whole selective color adjustment image. It is a block diagram which shows the 2nd Embodiment of this invention. It is explanatory drawing of an example of the target histogram according to a scene. It is explanatory drawing of an example of the scene of a color image. It is a block diagram which shows the 3rd Embodiment of this invention. It is a flowchart which shows an example of the operation | movement using the target color of the gradation conversion curve production | generation part 13 in the 3rd Embodiment of this invention. It is explanatory drawing of an example of the distance of a target color and a target color. It is explanatory drawing of an example of the storage medium which stored the computer program in the case of implement | achieving the function of the color adjustment apparatus or color adjustment method of this invention with a computer program, and the computer program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Selective color adjustment part, 12 ... Color distribution analysis part, 13 ... Tone conversion curve generation part, 14 ... Overall color adjustment part, 31 ... Program, 32 ... Computer, 41 ... Magneto-optical disk, 42 ... Optical disk, 43: magnetic disk, 44: memory, 51: magneto-optical disk device, 52: optical disk device, 53: magnetic disk device.

Claims (20)

  In a color adjustment apparatus for adjusting the color of a color image, selective color adjustment means for performing local color adjustment from a target color to be adjusted toward an adjustment target color, and color adjustment by the selective color adjustment means A color adjustment apparatus comprising overall color adjustment means for performing color adjustment on the entire color image.   In the color adjustment device for adjusting a color of a color image, the target color from the target color in a partial color space including a target color to be adjusted in the color space representing the color image and a target color to be adjusted And a color distribution for analyzing the color distribution of the selective color adjustment image which is a color image after the selective color adjustment by the selective color adjustment means A color adjustment apparatus comprising: an analysis unit; and an overall color adjustment unit that performs color adjustment on the entire selective color adjustment image according to the color distribution analyzed by the color distribution analysis unit.   3. The overall color adjustment unit performs color adjustment on the whole of the selective color adjustment image so that the color distribution analyzed by the color distribution analysis unit approaches a target color distribution. The color adjusting device described in 1.   The color adjustment apparatus according to claim 2, wherein the color distribution analysis unit represents the color distribution with a histogram for pixel values of the selective color adjustment image.   A gradation conversion curve generating unit configured to generate a gradation conversion curve such that the histogram approaches a target histogram, and the overall color adjusting unit includes the gradation conversion curve generated by the gradation conversion curve generating unit. The color adjustment apparatus according to claim 4, wherein color adjustment is performed on the whole of the selective color adjustment image using a color image.   The color adjustment apparatus according to claim 5, wherein the gradation conversion curve generation unit generates a curve for adjusting a color balance for the entire selective color adjustment image as the gradation conversion curve.   The gradation conversion curve generation unit controls the gradation conversion curve according to the importance of adjustment with respect to a target color to be adjusted or the importance of adjustment with respect to the entire color image. 5. The color adjusting device according to 5.   The color adjustment apparatus according to claim 5, wherein the gradation conversion curve generation unit controls the gradation conversion curve according to a scene represented by the color image.   The color adjustment apparatus according to claim 5, wherein the gradation conversion curve generation unit controls the gradation conversion curve according to at least one of the target color and the target color.   In the color adjustment method for adjusting the color of a color image, a color image in which local color adjustment from the target color to be adjusted toward the adjustment target color is performed by selective color adjustment means, and the local color adjustment is performed The color adjustment method is characterized in that the overall color adjustment is performed by the overall color adjustment means.   In the color adjustment method for adjusting a color of a color image, the target color from the target color in a partial color space including a target color to be adjusted in the color space representing the color image and a target color to be adjusted The selective color adjustment unit performs selective color adjustment toward the image, and the entire selective color adjustment image according to the color distribution of the selective color adjustment image which is a color image after the selective color adjustment is performed. The color adjustment method is characterized in that the overall color adjustment means performs the color adjustment for.   The color adjustment method according to claim 11, wherein color adjustment is performed on the entire selective color adjustment image so that the color distribution of the selective color adjustment image approaches a target color distribution.   The color adjustment method according to claim 11, wherein the color distribution is represented by a histogram with respect to pixel values of the selective color adjustment image.   The color adjustment method according to claim 13, wherein color adjustment is performed on the entire selective color adjustment image by using a gradation conversion curve such that the histogram approaches a target histogram.   The color adjustment method according to claim 14, wherein the gradation conversion curve is a curve for adjusting a color balance with respect to the entire selective color adjustment image.   The color adjustment method according to claim 14, wherein the gradation conversion curve is controlled in accordance with an importance level of adjustment with respect to a target color to be adjusted or an importance level of adjustment with respect to the entire color image. .   The color adjustment method according to claim 14, wherein the gradation conversion curve is controlled according to a scene represented by the color image.   The color adjustment method according to claim 14, wherein the gradation conversion curve is controlled according to at least one of the target color and the target color.   10. A color adjustment program for causing a computer to execute a color adjustment process for adjusting a color of a color image, wherein the function of the color adjustment apparatus according to any one of claims 1 to 9 or claims 10 to 10. A color processing program that causes a computer to execute the color adjustment method according to claim 18.   The function of the color adjustment apparatus according to any one of claims 1 to 9, in a computer-readable storage medium storing a color adjustment program for causing a computer to execute color adjustment processing for adjusting the color of a color image. A computer-readable storage medium storing a color adjustment program that causes a computer to execute the color adjustment method according to any one of claims 10 to 18.

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