JP2005269540A - Image processing apparatus and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus and a method thereof capable of dealing with input image data of a closed type input device-dependent color space and an open type device non-dependent color space, and capable of almost the same color reproduction between both the data. <P>SOLUTION: The input data of a closed type input device-dependent color space is subjected to color conversion into a standard input color reproduction region in an input standardizing section 1, then, subjected to color space conversion into a device non-dependent color space in an input color space converter 3, and subjected to color gamut compression into a color region corresponding to a standard output color reproduction gamut in a color processor 5. In contrast, the input image data of a device non-dependent color space is subjected to a color space conversion as necessary in a device non-dependent color space converter 4, and then, subjected to color gamut compression from a color region corresponding to a standard input color reproduction gamut to a color region corresponding to a standard output color reproduction gamut in the processor 5. The image data subjected to the color gamut compression are subjected to color space conversion into an output device-dependent color space in an output color space converter 6, and are converted into output image data of a color reproduction gamut for each output device in an output converter 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image processing technique for handling color digital images.

  With the spread of network systems, the opportunity to exchange images over the network has also increased. At the same time, the opportunity to output the same document on a plurality of different image output devices connected to a network is increasing.

  When printing with a plurality of output devices, there is often a problem that “the color of the output product is different”. This is because each output device has a different color gamut. When the same image is output from an output device with a different color gamut, each output device can output the same image. When the output results of are compared, the color is different from the allowable level.

  As a technique for solving such a problem, for example, in Patent Document 1, a common virtual common color gamut is provided in an output device, and input color data is once converted into a color within the virtual common color gamut (color gamut). A technique for performing color gamut compression on the color gamut of each output device after compression) is described. This minimizes the color difference reproduced by each output device.

  For example, as described in Patent Document 2, a standard color gamut is provided for the color space of the output device, a standard color gamut is provided for the color space of the input device, and input data is device-dependent. There is also a technique in which after conversion to a standard color gamut in the color space, the data is converted into data in the standard color gamut of the output device color space, and then converted into data in the color gamut corresponding to each output device.

However, these technologies alone are insufficient to handle images exchanged on the network. Generally, an image is described as data in a color space such as RGB, CMYK, or L ^* a ^* b ^* . However, a plurality of colors such as RGB and CMYK or RGB and L ^* a ^* b ^* are included in the same document. In some cases, spatial data is mixed. In the above-described prior art, it is assumed that all input data is data in the RGB color space. When data in another color space or data in which a plurality of color spaces are mixed is input. Was not considered.

In particular, sufficient image quality can be obtained in a document in which color data in which the color space itself is closed such as the RGB color space and color data in which the color space is open such as the L ^* a ^* b ^* color space are mixed. There is no problem. This is because the open color space such as the L ^* a ^* b ^* color space has a larger color gamut than the color gamut in the RGB color space. Although there are many color ranges that are not used in such an open color space, the color gamut is compressed to the color gamut of the output device in consideration of the possibility of being used, so the compression ratio becomes higher than necessary. The RGB color space data is also compressed into a narrow color gamut. As a result, the color gamut of the output device cannot be fully utilized. Conversely, when color gamut compression is performed by matching the color gamut of the RGB color space with the color gamut of the output device, the color of the RGB color space in an open color space such as the L ^* a ^* b ^* color space. For colors outside the reproduction range, satisfactory color reproduction cannot be performed, and there is a problem that image quality deteriorates.

JP 2002-252785 A JP 2000-50092 A

  The present invention has been made in view of the above-described circumstances, and can deal with input image data in a closed color space depending on a device and input image data in an open color space that is device-independent. It is an object of the present invention to provide an image processing apparatus and an image processing method capable of reproducing almost the same color with any output device for any input image data.

  According to the present invention, an input device-dependent color space color signal or a device-independent color space color signal is given as input image data, and the input image data is converted to output device-dependent color signal output image data. In the processing apparatus and the image processing method, when the input image data is an input device-dependent color signal, the input image data is a first intermediate in a common standard input color reproduction range defined in the input device-dependent color space. The image data is converted by the input standardization means, the first intermediate image data in the input device-dependent color space is converted by the first color space conversion means to the second intermediate image data in the device-independent color space, and the input image When the data is a device-independent color signal, the input image data is received or the second intermediate image data is received from the first color space conversion means. Thus, color gamut compression processing is performed on the color gamut in the device-independent color space corresponding to the common standard output color gamut defined in the output device-dependent color space, and converted to the third intermediate image data by the color processing means. The third intermediate image data is converted by the second color space conversion means into a fourth intermediate color signal that falls within the standard output color gamut in the output device-dependent color space, and the standard output color is converted in the output device-dependent color space. The fourth intermediate image data in the reproduction area is converted into the output image data in the color reproduction area of the output device by output conversion means.

  According to the present invention, a color signal in an input device-dependent color space or a color signal in a device-independent color space is given as input image data, and the input image data is converted into output image data of an output device-dependent color signal. In the image processing apparatus and the image processing method, when the input image data is an input device-dependent color signal, the input image data is converted into a first intermediate image data that is a color signal in a device-independent color space. Converting the first intermediate image data into second intermediate image data in a standard input color reproduction gamut common to input devices defined in a device-independent color space by the input standardization means, When the data is a device-independent color signal, the input image data is received or the second intermediate image data is received from the input standardization means A color gamut compression process to a standard output color gamut common to the output device is performed and converted into third intermediate image data by color processing means, and the third intermediate image data in the standard output color gamut is converted to the color of the output device. Converting to fourth intermediate image data in a color area corresponding to the reproduction area by output conversion means, and converting the fourth intermediate image data to output image data in an output device-dependent color space by second color space conversion means; It is characterized by.

  If the input image data is a color signal in a device-independent color space and the device-independent color space of the input image data is different from the device-independent color space handled by the color processing means, the third Color space conversion can be performed by color space conversion means, and the image data subjected to color space conversion can be converted to the third intermediate image data.

  In such an image processing apparatus and image processing method of the present invention, when color gamut compression processing is performed by the color processing means, color importance is important when the input image data is a color signal in a device-independent color space. It can be configured to perform color gamut compression processing according to the degree. For example, the device-independent color space includes a first region including a standard input color gamut composed of the most important colors and a first region among regions including a color gamut of one or more input devices. Divided into a second area composed of colors other than the first area and the third area composed of colors other than the first area, and color gamut compression corresponding to each area Processing can be performed. As the color gamut compression processing, first, for the color of the third region, the color gamut compression processing is performed on the color of the second region, and then the color gamut compression processing is performed on the color of the second region. For the colors of the first and second regions, first, the color of the first region is subjected to color gamut compression processing to the color gamut in the device-independent color space corresponding to the standard output color gamut. After applying the color gamut compression processing for the area to the second area, the color gamut compression processing to the color reproduction gamut in the device-independent color space corresponding to the standard output color reproduction gamut for colors outside the standard output color reproduction gamut I do. As a result, all colors can be converted to colors within the standard output color gamut.

  Further, the color adjustment processing corresponding to each data is performed on the first intermediate image data, when the color gamut compression processing is performed by the color processing means, or on the fourth intermediate image data. be able to.

  According to the present invention, the standard output color reproduction is performed both when the input image data of the closed device-dependent color space is given and when the input image data of the open device-independent color space is given. Since the color gamut compression processing is performed using the gamut and converted into the color gamut for each output device, the color reproduced by each output device regardless of the difference in the input device or the color space of the input image data. There is an effect that a good output image can be obtained by minimizing the difference. Further, even in the case of a document in which data having different color spaces are mixed, color conversion processing corresponding to each portion can be performed, and the difference in output colors due to mixing can be reduced.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, 1 is an input standardization unit, 2 is an input color adjustment unit, 3 is an input color space conversion unit, 4 is a device-independent color space conversion unit, 5 is a color processing unit, 6 is an output color space conversion unit, and 7 is An output color adjustment unit 8 is an output conversion unit. As input image data in the present invention, for example, a color signal in an input device-dependent color space such as RGB or a color signal in a device-independent color space such as CIEXYZ or CIELAB is given. When the input image data is a color signal in an input device-dependent color space, the input image data is input to the input standardization unit 1, and when the input image data is a color signal in a device-independent color space, a device-independent color space conversion unit 4 is used. Is input. For a document in which both are mixed, for each portion, the color signal portion of the input device-dependent color space is input to the input standardization unit 1, and the color signal portion of the device-independent color space is input. Is input to the device-independent color space conversion unit 4. The output image data is a color signal in an output device-dependent color space. In the following description, it is assumed that RGB or CIEXYZ color signals are input as input image data, and YMCK color signals are output as output image data. Of course, it is needless to say that the present invention is not limited to these, and each of the input device-dependent color space, the device-independent color space, and the output device-dependent color space may correspond to a plurality of color spaces.

  The input standardization unit 1 receives input image data in an input device-dependent color space, and converts the input image data into first intermediate image data in a common standard input color gamut defined in the input device-dependent color space. .

  The input color adjustment unit 2 performs color adjustment on the first intermediate image data in the input device-dependent color space as necessary. As color adjustment, for example, brightness adjustment, contrast adjustment, saturation adjustment, and γ correction can be performed. The input color adjusting unit 2 may be omitted.

  The input color space conversion unit 3 performs color space conversion from the input device-dependent color space to the device-independent color space for the first intermediate image data in the input device-dependent color space that has been appropriately color-adjusted. 2 Convert to intermediate image data. For example, color space conversion from RGB to CIELAB can be performed.

  The device-independent color space conversion unit 4 receives input image data in the device-independent color space, and performs color space conversion into a device-independent color space handled by the color processing unit 5. For example, color space conversion from CIEXYZ to CIELAB can be performed. If the device-independent color space of the input image data is originally the same as the device-independent color space handled by the color processing unit 5, color space conversion processing by the device-independent color space conversion unit 4 is not necessary. If this color space conversion process is not always necessary, the device independent color space conversion unit 4 may be omitted.

  The color processing unit 5 receives the second intermediate image data from the color space conversion unit 3, or receives the input image data color space converted as necessary by the device-independent color space conversion unit 4, and outputs the output device-dependent color A color gamut compression process is performed on the color gamut in the device-independent color space corresponding to the common standard output color gamut defined in the space, and converted into third intermediate image data. Regarding the second intermediate image data, since the color of the standard input color gamut defined in the input device-dependent color space is converted into the device-independent color space, the corresponding closure is also performed in the device-independent color space. The color is in the area. Therefore, the color gamut compression processing from the color of the closed region to the color of the closed region is performed. On the other hand, in the case of input image data in a device-independent color space, since the device-independent color space is an open color space, the color of the open area is converted to the color of the closed area. . Of course, the input image data value in the device-independent color space is limited, but there is a possibility that data of a considerably wide area other than the color range that can be actually reproduced may be input. The color is converted to a color in a closed area corresponding to the standard output color reproduction area. However, since there are many color areas that are rarely used, color gamut compression processing according to the importance of colors as described later can be performed.

  The color processing unit 5 can perform color adjustment when performing color gamut compression processing. As color adjustment processing performed by the color processing unit 5, processing that can be easily corrected by handling image data in a device-independent color space, such as hue angle adjustment, lightness adjustment, and saturation adjustment, can be performed. Of course, the color adjustment is optional and may not be performed.

  The output color space conversion unit 6 receives the third intermediate image data from the color processing unit 5, performs a color space conversion from the device-independent color space to the output device-dependent color space for the third intermediate image data, Converts to 4 intermediate color signals. As described above, since the color processing unit 5 converts the color into the color corresponding to the standard output color gamut to obtain the third intermediate image data, the fourth intermediate image data is in the standard output color gamut in the output device-dependent color space. It is a color.

  The output color adjustment unit 7 performs color adjustment as necessary on the fourth intermediate image data in the output device-dependent color space. As color adjustment, color balance adjustment, density adjustment, and the like can be performed. The output color adjusting unit 7 may be omitted.

  For the fourth intermediate image data in the output device-dependent color space that has been appropriately color-adjusted, the output conversion unit 8 converts the color in the standard output color gamut to the color in the color gamut of the output device that actually outputs the image. A color gamut compression process is performed so that the output image data is converted and output. This output image data is passed to the output device, and an image is output according to the output image data.

  FIG. 2 is an explanatory diagram of an example of the operation according to the first embodiment of this invention. In particular, FIG. 2 mainly shows the transition of the color space of each image data. In this example, as shown in FIG. 2A, as input image data, image data in the device color space of the input device a, image data in the device color space of the input device b, and image data in the device-independent color space Shows an example of a mixture of. Among these, the image data in the device color space of the input device a and the input device b is converted into the first intermediate image data in the standard input color reproduction range by the input standardization unit 1 (FIG. 2B). For example, when both the input devices a and b output image data in the RGB color space, the colors are often different even if the values of the image data are the same, and the color gamuts are often different. Conversion processing is performed to match different colors and color reproduction ranges for each input device with the standard input color reproduction range. For example, the sRGB color space can be used as a color space for realizing the standard input color reproduction range. By obtaining image data in the RGB color space depending on the input devices a and b into image data in the sRGB color space, which is a standardized RGB color space, common first intermediate image data independent of the input device is obtained. Can do.

  After the input color adjustment unit 2 appropriately performs color adjustment on the first intermediate image data, the input color space conversion unit 3 converts the first intermediate image data into second intermediate image data that is image data in a device-independent color space (see FIG. 2 (C)). Since the first intermediate image data before conversion is image data in the standard input color gamut in the input device-dependent color space, the second intermediate image data converted into the device-independent color space also supports the standard input color gamut. The image data is in the color area.

  Next, the color processing unit 5 converts the second intermediate image data in the color region corresponding to the standard input color reproduction range to the third intermediate image data in the color region corresponding to the standard output color reproduction range (FIG. 2 ( C) in). FIG. 3 is an explanatory diagram of an example of a color area corresponding to the standard input color reproduction area and the standard output color reproduction area in the device-independent color space. FIG. 3 shows a hue section in a device-independent color space. A color region indicated by a broken line in FIG. 3 is a color region corresponding to the standard input color reproduction region defined in the input device-dependent color space. Further, the color area indicated by the solid line in FIG. 3 is a color area corresponding to the standard output color reproduction area defined in the output device-dependent color space. The color processing unit 5 performs color gamut compression processing for converting the color of the color area indicated by the broken line in FIG. 3 into the color of the color area indicated by the solid line.

  As the color gamut compression process, various known methods such as a lightness preservation method, a saturation preservation method, a target point compression method, or a combination thereof can be used. For example, as described in JP-A-2002-152538, it is possible to apply a method of performing color conversion processing using a target point compression method after performing hue adjustment processing and lightness adjustment processing. The outline of the color gamut compression process will be described below.

  FIG. 4 is a conceptual diagram of the hue adjustment process. The input image data input by the input device is created by the hue angle affected by the input device. Although the second intermediate image data converted into the device-independent color space also depends on the processing content when converted into the standard input color reproduction gamut, the hue angle remains affected by the common input device. By adjusting the deviation of the hue angle, color reproducibility in input / output image data can be improved.

As shown in FIG. 4, this hue adjustment can be performed only by rotating around the L ^* axis in the CIELAB color space. For example, the color of point a shown in FIG. 4 is changed to the color of point a by rotational movement. Note that the rotation angle and the rotation direction at this time are determined according to the hue of the input color image signal. For example, magenta (M) is largely moved in a direction approaching red (R). Further, blue (B) may be moved largely in a direction approaching cyan (C). Conversely, yellow (Y) needs almost no change in hue.

  FIG. 5 is an explanatory diagram of an example of brightness adjustment processing. In the figure, the broken line and the solid line are the same as those in FIG. First, the standard input color gamut is adjusted so that the brightness range of the color area corresponding to the standard input color gamut, that is, the maximum value to the minimum value of the brightness is matched to the brightness range of the color area corresponding to the standard output color gamut The brightness direction is adjusted for the entire color region corresponding to. As a result, the color area corresponding to the standard input color reproduction area becomes as shown by the broken line in FIG.

  Further, the brightness of the point (CUSPi) having the maximum saturation in the color area corresponding to the standard input color reproduction area after the adjustment of the lightness range as described above, and the color area corresponding to the standard output color reproduction area The point (CUSpi) is adjusted by a predetermined function within a range of the difference from the lightness of the point having the maximum saturation (CUSPo), and the lightness direction of the entire color region corresponding to the standard input color reproduction region is adjusted accordingly. Process. For example, the lightness of the point (CUSPi) having the maximum saturation is adjusted from the color region indicated by the broken line in FIG. 5B, and is adjusted to the color region indicated by the broken line in FIG.

  In this way, after the colors in the color area corresponding to the standard input color reproduction range indicated by the broken line in FIG. 5A are converted into the colors in the color area indicated by the broken line in FIG. 5C, FIG. ) Is converted to a color in the color area corresponding to the standard output color reproduction area indicated by the solid line. For example, if the lightness of the point (CUSPo) having the maximum saturation in the color region corresponding to the standard output color gamut is higher than the color region corresponding to the standard output color gamut, a predetermined value is set with respect to the saturation axis. Is compressed toward the outline of the color area corresponding to the standard output color gamut, and the color area corresponding to the standard output color gamut is converted only for the saturation while maintaining the lightness. When the brightness is lower than the point (CUSPo), the target point is an achromatic color having a predetermined brightness, and the brightness and saturation are converted in a straight line direction connecting the color image signal color after the brightness adjustment and the target point. Can be processed.

  The third intermediate image data (in FIG. 2C) that has been subjected to the color gamut compression processing in the color region corresponding to the standard output color reproduction region in this way is output by the output color space conversion unit 6 in the output device dependent color space. It is spatially converted to become the fourth intermediate image data (FIG. 2D). Since the third intermediate image data is color gamut compressed into a color area corresponding to the standard output color gamut, the fourth intermediate image data subjected to color space conversion becomes image data in the standard output color gamut. Yes. Note that the output color adjustment unit 7 can appropriately perform color adjustment on the fourth intermediate image data.

  Finally, the output conversion unit 8 converts the fourth intermediate image data in the standard output color gamut with appropriate color adjustment into output image data in the color gamut of each output device (FIG. 2 (E)). Output to the output device. Although FIG. 2 shows the output device c and the output device d, each output can be obtained by converting the standard output color gamut to the color gamut of each output device even if the color gamuts are different. Optimal color reproduction is possible on the device.

  On the other hand, the device-independent color space image data in the input image data is converted into the device-independent color space image data used by the color processing unit 5 by the device-independent color space conversion unit 4. When the input image data is image data in the CIEXYZ color space and the color processing unit 5 uses image data in the CIELAB color space, color space conversion from the CIEXYZ color space to the CIELAB color space may be performed. Of course, if the color space of the input image data matches the color space used by the color processing unit 5, the color space conversion by the device-independent color space conversion unit 4 is unnecessary.

  The color processing unit 5 receives input image data of a device-independent color space that has been color space converted as necessary, performs a color gamut compression process on a color region corresponding to the standard output color reproduction gamut, and performs a third intermediate image. Data. At this time, since the device-independent color space is an open type, even if the color value is finite, for example, a wider color region can be taken compared to the input device-dependent color space. For example, in the case of a certain hue plane shown in FIG. 3, the value of the entire two-dimensional plane including the color area corresponding to the standard input color reproduction range and the standard output color reproduction range shown in the figure can be taken. Therefore, a color in a wide color area must be compressed into a color area corresponding to a narrow standard output color reproduction area. However, if the compression is performed uniformly, the compression becomes excessive and the color reproducibility deteriorates. In addition, consistency with the input image data in the input device-dependent color space cannot be obtained. For this reason, here, a color gamut compression process according to the importance of the color is performed. As one of the methods, a method described in JP 2002-152538 A can be applied. The outline of this method will be described below.

FIG. 6 is an explanatory diagram of an example of a plurality of color regions set by the color processing unit according to the importance of the color. In FIG. 6, a CIELAB color space is assumed as the device-independent color space, and a hue plane including the L ^* axis is shown. A broken line indicates a color area corresponding to the standard input color reproduction area.

  A region A indicates a region including a color important for color reproduction. For example, the area A is preferably an area including a color area corresponding to the standard input color reproduction area. The area B is an area including the next most important color after the area A. For example, the area B includes a color area corresponding to the color reproduction area of one or more input devices, and may be a color area not included in the area A. . Since the color of the area B is not always used, the importance is lower than the color in the area A. However, the color of the area B may be used depending on the input device. Is a required area. For this reason, the color conversion process is performed so that a satisfactory color reproduction is performed so as not to affect the color conversion process of the region A. Region C is a region other than region A and region B. The color in this area is rarely used and is a color with low importance. However, for example, when the user designates by numerical value setting or generates data by numerical value by software or the like, the color may be input. For this reason, it is necessary to reproduce an appropriate color when input, and color conversion processing for that purpose may be performed. In this example, an example in which the area is divided into three areas is shown. However, the present invention is not limited to this. For example, the area may be divided into two or four or more areas.

  First, the color gamut compression process for the colors in the area A is the same process as the color gamut compression process from the color area corresponding to the standard input color reproduction area to the color area corresponding to the standard output color reproduction area. Just do it. As a result, the color having high importance can be matched with the input image data in the input device-dependent color space.

  For the colors in the area B, after applying the same method as the colors in the area A, the color gamut compression processing is further performed on the colors outside the color area corresponding to the standard output color gamut. More specifically, after performing the hue angle adjustment as described in FIG. 4 and the brightness adjustment process as described in FIG. 5, the point having the maximum saturation in the color region corresponding to the standard output color reproduction region (CUSPo) The color gamut compression processing is performed by the respective methods depending on whether the brightness is higher than or lower than the brightness.

FIG. 7 is an explanatory diagram of an example of color conversion processing for the image data in the region B. FIG. 7A shows a case where the brightness of the image data after the brightness adjustment is higher than the brightness of the point (CUSPo), and FIG. 7B shows the brightness of the image data after the brightness adjustment from the brightness of the point (CUSPo). It shows the case where it is low. When the brightness of the image data after the brightness adjustment is higher than the brightness of the point (CUSPo), a straight line that passes through a point (shown by a black circle) indicating the color image signal after the brightness adjustment and forms a predetermined angle with the saturation axis The intersection (indicated by a black triangle) between this straight line and the outline of the color area corresponding to the standard output color reproduction area is obtained. Further, consider a straight line that passes through the intersection of a straight line that forms a predetermined angle with the saturation axis and the outline of the color region corresponding to the standard output color gamut and is orthogonal to the L ^* axis (this straight line preserves brightness). Each distance is calculated in accordance with the path bent at the intersection obtained in this way.

  When color gamut compression processing is performed in such a manner and the color on the outline of the area A (shown by a black triangle) is converted into the outline of the color area corresponding to the standard output color reproduction area, the color outside the area A Becomes a color outside the color region corresponding to the standard output color reproduction region (indicated by a white circle). Therefore, the second color gamut compression process is performed so as to be a point in the color region corresponding to the standard output color reproduction region. As the second color gamut compression process, for example, a color difference minimum method or the like can be used.

  In this way, the colors in the region B can be converted into the colors in the color region corresponding to the standard output color reproduction region by the two-step color gamut compression processing in this example. Of course, the method is not limited to this method. For example, the region A and the region B are integrated into a color region corresponding to the standard output color reproduction region, and the compression rate at this time is low in the region A. A method of setting a high value in the area B is also applicable.

  The color in the area C is an area of a color that is rarely used normally, and therefore, it may be converted so that an appropriate color is reproduced. For example, the color can be converted into the outline color of the region B while maintaining the brightness, and then the color gamut compression processing can be performed in the same manner as the color in the region B. Of course, other methods may be applied.

  In this way, the colors in the respective areas shown in FIG. 6 can be compressed into the colors in the color area corresponding to the standard output color reproduction area. At this time, color reproducibility is improved by performing processing according to the importance of each color. Further, the color reproduction can be continued as much as possible by linking the color gamut compression processing of each region, and good color reproduction can be realized. Furthermore, it is possible to achieve consistency with input image data in the input device-dependent color space.

  As described above, color gamut compression processing is performed, and third intermediate image data that is color gamut-compressed into a color region corresponding to the standard output color reproduction gamut is obtained. Thereafter, as in the case of the input image data in the input device-dependent color space, the output color space conversion unit 6 performs color space conversion to the output device-dependent color space to obtain fourth intermediate image data, and the output color adjustment unit 7 selects an appropriate color. After the adjustment, the output converter 8 may convert the output image data in the color gamut of each output device.

  As described above, according to the first embodiment described above, whether the input image data is image data in a closed input device-dependent color space or image data in an open device-independent color space, Output image data corresponding to each output device can be obtained, and an image can be output with good image quality in each output device. Further, even if input image data is a mixture of image data in the input device-dependent color space and image data in the device-independent color space, better color reproduction can be achieved by performing optimum processing for each.

  FIG. 8 is a block diagram showing a second embodiment of the present invention. The reference numerals in the figure are the same as those in FIG. In the first embodiment described above, the color area of each input device is converted into the standard input color gamut in the input device dependent color space, and the standard output color gamut is converted into each output device in the output device dependent color space. Converted to the color area. In the second embodiment, input image data corresponding to each input device is color space converted into a device-independent color space and then converted into a standard input color reproduction gamut, and a standard output color in the device-independent color space. An example is shown in which the reproduction area is converted into the color area of each output device and then converted into the output device-dependent color space.

  The input color space conversion unit 3 converts input image data in the input device-dependent color space into first intermediate image data in a device-independent color space. The first intermediate image data directly reflects the color gamut in each input device, and the color gamut in the device-independent color space differs depending on which input device is the input image data.

  The input color adjustment unit 2 appropriately performs color adjustment on the first intermediate image data in the device-independent color space. As the color adjustment, for example, brightness adjustment, contrast adjustment, saturation adjustment, and the like can be performed. Of course, if it is not necessary to perform color adjustment, the input color adjustment unit 2 may not be provided.

  The input standardization unit 1 converts the color gamut corresponding to each input device into the standard input color gamut common to the input devices for the first intermediate image data that has been appropriately color-adjusted to obtain the second intermediate image. Data. In the second embodiment, the standard input color gamut is a color area defined in a device-independent color space.

  The device-independent color space conversion unit 4 is the same as that in the first embodiment described above, receives input image data in a device-independent color space, and converts the color space into a device-independent color space handled by the color processing unit 5 I do. Of course, when the device-independent color space of the input image data is the same as the device-independent color space originally handled by the color processing unit 5, the color space conversion processing by the device-independent color space conversion unit 4 is not necessary. If this color space conversion process is not always necessary, the device independent color space conversion unit 4 may be omitted.

  The color processing unit 5 receives the second intermediate image data from the input standardization unit 1 or receives the input image data that has been color space converted by the device-independent color space conversion unit 4 as necessary, and is a standard common to the output devices. A color gamut compression process is performed on the output color reproduction gamut to convert it into third intermediate image data. The standard output color reproduction area is also a color area defined in the device-independent color space in the second embodiment. Note that the color gamut compression processing may be the same as in the first embodiment.

  The output conversion unit 8 converts the third intermediate image data in the standard output color gamut into a color region in a device-independent color space corresponding to the color gamut of each output device, and generates fourth intermediate image data. In the second embodiment, this color conversion is performed in a device-independent color space.

  The output color adjustment unit 7 appropriately performs color adjustment on the fourth intermediate image data. As the color adjustment, since the fourth intermediate image data is already image data corresponding to the color gamut of each output device, various color adjustments corresponding to each output device can be performed. For example, when the output device is a printing apparatus that uses ink, toner, or the like, total amount restriction processing for the ink, toner, or the like can be performed. Of course, if color adjustment is not necessary, adjustment processing is unnecessary, and the output color adjustment unit 7 may be omitted.

  The output color space conversion unit 6 converts the fourth intermediate image data in the device-independent color space into output image data in the output device-dependent color space, and outputs the output image data to the output device.

  FIG. 9 is an explanatory diagram of an example of the operation according to the second embodiment of the present invention. 9 also shows the transition of the color space of each image data, as in FIG. The input image data is the same as that shown in FIG. 2A. The image data in the device color space of the input device a, the image data in the device color space of the input device b, and the image data in the device-independent color space are mixed. An example is shown.

  Of the input image data, the image data in the device color space of the input device a and the image data in the device color space of the input device b are color space converted into a device-independent color space by the input color space conversion unit 3 and are first. Intermediate image data is obtained (FIG. 9B). FIG. 10 is an explanatory diagram showing an example of the relationship between the color area corresponding to the color gamut of each input device in the device-independent color space and the standard input color gamut. Since each input device has a unique color gamut, when converted to a device-independent color space, image data of a color region corresponding to the color gamut of each input device is obtained. In FIG. 10, a solid line indicates a color area corresponding to the color gamut of the input device a, and a dashed line indicates a color area corresponding to the color gamut of the input device b. As described above, the color regions corresponding to the color gamuts of the respective input devices are different. At this point, color adjustment corresponding to each input device can be performed.

  As described above, the first intermediate image data of the color region corresponding to the color gamut of each input device is converted from the color region corresponding to the color gamut of each input device to the standard input color gamut in the input standardization unit 1. Is converted into second intermediate image data (FIG. 9C). In FIG. 10, the standard input color gamut is indicated by a broken line, and at least colors outside the standard input color gamut are converted to become colors within the standard input color gamut.

  The second intermediate image data in the standard input color gamut is subjected to color gamut compression processing from the standard input color gamut to the standard output color gamut in the color processing unit 5 and converted into third intermediate image data ( FIG. 9D). Since the color gamut compression processing in the color processing unit 5 is the same as that in the first embodiment described above, description thereof is omitted here.

  The third intermediate image data of the standard output color reproduction gamut that has been subjected to the color gamut compression processing by the color processing unit 5 is converted into a color region corresponding to the color reproduction gamut of each output device by the output conversion unit 8 to obtain the fourth intermediate image. Data is used (FIG. 9E). FIG. 11 is an explanatory diagram showing an example of the relationship between the standard output color gamut and the color gamut corresponding to the color gamut of each input device in the device-independent color space. A solid line indicates a standard output color gamut, and a broken line and an alternate long and short dash line indicate color areas corresponding to the color gamuts of the output devices c and d, respectively. As shown in FIG. 11, the output devices may have different color gamuts, and the output conversion unit 8 converts the standard output color gamut to the optimum color gamut for each output device. Accordingly, the fourth intermediate image data is image data of a color region that differs depending on the output target.

  As described above, the fourth intermediate image data corresponding to the color gamut of each output device is appropriately color-adjusted by the output color adjusting unit 7 and then color space converted by the output color space converting unit 6 to the output device-dependent color space. And output image data (FIG. 9F). This output image data is image data corresponding to the color gamut of each output device. The output image data is transferred to each corresponding output device, and an image is output.

  On the other hand, as for the image data in the device-independent color space in the input image data, the device-independent color space color is converted by the device-independent color space conversion unit 4 as necessary, as in the first embodiment. After performing the space conversion process, the color processing unit 5 performs the color gamut compression process to the standard output color reproduction gamut to obtain third intermediate image data. The color gamut compression process at this time may be performed in the same manner as in the first embodiment.

  The third intermediate image data that has been color gamut-compressed into the standard output color reproduction gamut is output to each output device by the output conversion unit 8 as in the case where the input image data is image data in the input device-dependent color space. Are converted into the fourth intermediate image data of the color area corresponding to the color reproduction area in FIG. 5, and after the color adjustment is appropriately performed by the output color adjustment unit 7, the output image of the output device dependent color space is output by the output color space conversion unit 6. Color space converted to data. Then, output image data is passed to the output device to be output, and an image is output from the output device.

  As described above, in the second embodiment, as in the first embodiment, even when the input image data is image data in a closed input device-dependent color space, an open-type device-independent color is used. Even in the case of spatial image data, output image data corresponding to each output device can be obtained, and an image can be output with good image quality on each output device. Further, even if input image data is a mixture of image data in the input device-dependent color space and image data in the device-independent color space, better color reproduction can be achieved by performing optimum processing for each.

  The first embodiment and the second embodiment described above are combined. For example, on the input side, conversion to the standard input color gamut is performed in the input device-dependent color space as in the first embodiment. On the output side, it is possible to perform conversion to the standard output color gamut in the device-independent color space, and vice versa.

It is a block diagram which shows the 1st Embodiment of this invention. It is explanatory drawing of an example of the operation | movement in the 1st Embodiment of this invention. It is explanatory drawing of an example of the color area corresponding to the standard input color reproduction range in a device independent color space, and a standard output color reproduction range. It is a conceptual diagram of a hue adjustment process. It is explanatory drawing of an example of a brightness adjustment process. It is explanatory drawing of an example of several color area | region set according to the importance of a color in a color processing part. FIG. 10 is an explanatory diagram illustrating an example of color conversion processing for image data in a region B. It is a block diagram which shows the 2nd Embodiment of this invention. It is explanatory drawing of an example of the operation | movement in the 2nd Embodiment of this invention. It is explanatory drawing of an example of the relationship between the color area corresponding to the color reproduction range of each input device in a device independent color space, and a standard input color reproduction range. It is explanatory drawing of an example of the relationship of the color area corresponding to the color reproduction range of each input device in a standard output color reproduction range and a device independent color space.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Input standardization part, 2 ... Input color adjustment part, 3 ... Input color space conversion part, 4 ... Device independent color space conversion part, 5 ... Color processing part, 6 ... Output color space conversion part, 7 ... Output color adjustment Unit, 8... Output conversion unit.

Claims (24)

  In an image processing apparatus that receives a color signal in an input device-dependent color space or a color signal in a device-independent color space as input image data, and converts the input image data into output image data of an output device-dependent color signal. When the input image data is an input device-dependent color signal, the input standardization unit converts the input image data into first intermediate image data in a common standard input color reproduction range defined in the input device-dependent color space. First color space conversion means for converting the first intermediate image data in the input device-dependent color space into second intermediate image data in the device-independent color space; and the input image data is a device-independent color signal If the input image data is received or the second intermediate image data is received from the first color space conversion means, the output device depends Color processing means for performing color gamut compression processing on a color reproduction gamut in a device-independent color space corresponding to a common standard output color reproduction gamut defined in the color space and converting it into third intermediate image data; and the third intermediate Second color space conversion means for converting image data into a fourth intermediate color signal that falls within the standard output color gamut in an output device dependent color space; and the fourth color space within the standard output color gamut in an output device dependent color space. An image processing apparatus comprising output conversion means for converting intermediate image data into the output image data in a color gamut of an output device.   In an image processing apparatus that receives a color signal in an input device-dependent color space or a color signal in a device-independent color space as input image data, and converts the input image data into output image data of an output device-dependent color signal. A first color space conversion means for converting the input image data into first intermediate image data that is a color signal of a device-independent color space when the input image data is an input device-dependent color signal; Input standardization means for converting the intermediate image data into second intermediate image data in a standard input color reproduction range common to input devices defined in a device-independent color space; and the input image data is a device-independent color signal. In some cases, the input image data is received or the second intermediate image data is received from the input standardization means and is shared by the output devices. Color processing means for performing color gamut compression processing to the quasi-output color gamut and converting it to third intermediate image data; and color corresponding to the color gamut of the output device for the third intermediate image data in the standard output color gamut An image having output conversion means for converting into fourth intermediate image data in the area, and second color space conversion means for converting the fourth intermediate image data into output image data in a color space dependent on an output device Processing equipment.   Furthermore, it has a third color space conversion means for performing color space conversion when the device independent color space of the input image data is different from the device independent color space handled by the color processing means, and the color processing means When the input image data is a color signal in a device-independent color space, the image data that has undergone color space conversion by the third color space conversion means is received and converted to the third intermediate image data. The image processing apparatus according to claim 1 or 2.   4. The color processing unit according to claim 1, wherein when the input image data is a color signal in a device-independent color space, the color processing unit performs color gamut compression processing according to the importance of the color. The image processing apparatus according to any one of the above.   When the input image data is a color signal of a device-independent color space, the color processing means defines the device-independent color space as a first region composed of the most important colors, and the first It is divided into a second region composed of the next most important color among the colors other than the region and a third region composed of the other colors, and color gamut compression processing is performed according to each region. The image processing apparatus according to claim 4.   The image processing apparatus according to claim 5, wherein the first area includes the standard input color reproduction area.   The image according to claim 5 or 6, wherein the second region is a region other than the first region among regions including a color reproduction region of one or more input devices. Processing equipment.   The color processing means performs color gamut compression processing on the color of the second region after performing color gamut compression processing on the color of the third region to the color of the second region. The image processing apparatus according to any one of claims 5 to 7.   The color processing means performs a color gamut compression process on a color gamut in a device-independent color space corresponding to the standard output color gamut for the color of the first area, and a color gamut for the first area. After applying compression processing to the second region, color gamut compression processing to a color reproduction gamut in a device-independent color space corresponding to the standard output color reproduction gamut with respect to a color outside the standard output color reproduction gamut. The image processing apparatus according to claim 5, wherein the image processing apparatus is performed.   The image processing apparatus according to claim 1, further comprising a first color adjustment unit that performs color adjustment on the first intermediate image data.   The image processing apparatus according to claim 1, wherein the color processing unit performs color adjustment when performing the color gamut compression processing.   The image processing apparatus according to claim 1, further comprising a second color adjustment unit that performs color adjustment on the fourth intermediate image data.   In an image processing method in which a color signal in an input device-dependent color space or a color signal in a device-independent color space is given as input image data, and the input image data is converted into output image data of an output device-dependent color signal. When the input image data is an input device-dependent color signal, the input image data is converted by the input standardization means into first intermediate image data within a common standard input color gamut defined in the input device-dependent color space. The first intermediate image data in the input device-dependent color space is converted into second intermediate image data in the device-independent color space by the first color space conversion means, and the input image data is converted into a device-independent color signal. If the input image data is received or the second intermediate image data is received from the first color space conversion means, the output device-dependent color Color gamut compression processing to a color gamut in a device-independent color space corresponding to a common standard output color gamut defined between them, converted into third intermediate image data by color processing means, and the third intermediate image Data is converted by a second color space conversion means into a fourth intermediate color signal that falls within the standard output color gamut in an output device dependent color space, and the fourth intermediate in the standard output color gamut in an output device dependent color space. An image processing method comprising: converting image data into the output image data in a color gamut of an output device by output conversion means.   In an image processing method in which a color signal in an input device-dependent color space or a color signal in a device-independent color space is given as input image data, and the input image data is converted into output image data of an output device-dependent color signal. When the input image data is an input device-dependent color signal, the input image data is converted into first intermediate image data that is a color signal of a device-independent color space by a first color space conversion unit, and the first The intermediate image data is converted to second intermediate image data in a standard input color reproduction range common to input devices defined in a device-independent color space by input standardization means, and the input image data is a device-independent color signal. In some cases, the input image data is received or the second intermediate image data is received from the input standardization means, and a standard common to the output devices is received. A color area corresponding to the color gamut of the output device is converted into third intermediate image data by color processing means by performing color gamut compression processing to the force color gamut, and the third intermediate image data in the standard output color gamut An image processing method comprising: converting the fourth intermediate image data into output image data in an output device-dependent color space by using the second color space conversion means. .   When the input image data is a color signal of a device-independent color space, a third color space conversion is performed when the device-independent color space of the input image data is different from the device-independent color space handled by the color processing means. 15. The image processing method according to claim 13, wherein color space conversion is performed by a means, and the color space converted image data is converted to the third intermediate image data.   14. The color gamut compression processing according to claim 13, wherein, when the input image data is a color signal in a device-independent color space, the color gamut compression processing is performed according to the importance of the color. The image processing method according to claim 15.   As the color gamut compression processing, when the input image data is a color signal of a device-independent color space, the device-independent color space is defined as a first region composed of the most important colors; The color area is divided into a second area composed of the next most important color, and a third area composed of the other colors, and a color gamut compression process corresponding to each area is performed. The image processing method according to claim 16.   The image processing method according to claim 17, wherein the first area includes the standard input color reproduction area.   The image according to claim 17 or 18, wherein the second region is a region other than the first region among regions including a color reproduction region of one or more input devices. Processing method.   20. The color gamut compression processing is performed on the color of the second region after the color gamut compression processing is performed on the color of the third region to the color of the second region. The image processing method according to any one of the above.   A color gamut compression process is performed on a color reproduction gamut in a device-independent color space corresponding to the standard output color reproduction gamut for the color in the first area, and a color gamut compression process on the first area is performed on the second area. After being applied to the area, a color gamut compression process is performed on a color that is out of the standard output color gamut to a color gamut in a device-independent color space corresponding to the standard output color gamut. The image processing method according to any one of claims 17 to 20.   The image processing method according to any one of claims 13 to 21, further comprising performing color adjustment on the first intermediate image data.   The image processing method according to any one of claims 13 to 21, wherein color adjustment is performed when the color gamut compression processing is performed.   The image processing method according to any one of claims 13 to 21, further comprising performing color adjustment on the fourth intermediate image data.

Images