Image processing apparatus, image processing method, image processing program, storage medium and computer data signal

Abstract

An image processing apparatus performs color conversion processing on an input image. The image processing apparatus includes a block pallet conversion unit, a first color converting unit and a restoration unit. The block pallet conversion unit converts the input image in units of blocks into (i) pallet color information including pallet colors number of which is less than pixels included in one of the blocks and (ii) selection information used to select one of the pallet colors for each pixel. The first color converting unit performs color conversion on the pallet color information obtained by the block pallet conversion unit. The restoration unit selects for each pixel, based on the selection information, one of the pallet colors of the pallet color information, which is color-converted by the first color converting unit, to restores an image.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in detail based on the following figures, wherein:

FIG. 1 is a block diagram showing a first exemplary embodiment of the invention;

FIG. 2 is an explanatory diagram showing a specific example of the operation of the first exemplary embodiment of the invention;

FIG. 3 is a block diagram showing an example of an attribute judgment section;

FIG. 4 is a block diagram showing a second exemplary embodiment of the invention;

FIG. 5 is a block diagram showing a modification of the second exemplary embodiment of the invention;

FIG. 6 is a block diagram showing another modification of the second exemplary embodiment of the invention;

FIG. 7 is a block diagram showing a third exemplary embodiment of the invention;

FIG. 8 is an explanatory diagram showing a computer program as an implementation of the functions of the image processing apparatus according to the exemplary embodiments of the invention or the image processing method according to the exemplary embodiments of the invention as well as exemplary storage media in which the computer program is stored; and

FIG. 9 illustrates an exemplary color conversion method using a DLUT.

Claims

1. An image processing apparatus for performing color conversion processing on an input image, the image processing apparatus comprising: a block pallet conversion unit that converts the input image in units of blocks into (i) pallet color information including pallet colors number of which is less than pixels included in one of the blocks and (ii) selection information used to select one of the pallet colors for each pixel; anda first color converting unit that performs color conversion on the pallet color information obtained by the block pallet conversion unit; anda restoration unit that selects for each pixel, based on the selection information, one of the pallet colors of the pallet color information, which is color-converted by the first color converting unit, to restores an image.

2. The apparatus according to claim 1, further comprising: a second color converting unit that performs color conversion on the input image; andan output image generating unit that generates an output image based on at least one of the image restored by the restoration unit and the image color-converted by the second color converting unit.

3. The apparatus according to claim 2, further comprising: a filtering unit that extracts an edge from the input image and performs adaptive filtering on the input image, wherein:the second color converting unit performs the color conversion on the image filtered by the filtering unit.

4. The apparatus according to claim 2, further comprising: an attribute judging unit that judges an attribute of each region of the input image, wherein:the output image generating unit selects for each region either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with the attribute of the corresponding region judged by the attribute judging unit, to generate the output image.

5. The apparatus according to claim 4, wherein: the input image is data written in printer description language, andthe attribute judging unit interprets the data written in the printer description language to judge the attribute of each region.

6. The apparatus according to claim 4, wherein: the output image generating unit selects the image color-converted by the second color converting unit, for a region, which the attribute judging unit judges as a text/line-drawing region, andthe output image generating unit selects the image restored by the restoration unit, for a region, which the attribute judging unit judges as a photograph region.

7. The apparatus according to claim 2, wherein the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with a processing mode, to generate the output image.

8. The apparatus according to claim 2, wherein the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with a document mode, to generate the output image.

9. The apparatus according to claim 2, wherein the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with a color mode, to generate the output image.

10. The apparatus according to claim 3, wherein: the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with a color mode, to generate the output image, andthe output image generating unit selects the image, which is filtered by the filtering unit and not subjected to the color conversion of the second color converting unit if the color mode is a black-and-white mode.

11. The apparatus according to claim 2, wherein the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with a processing speed mode indicating whether priority is attached to the processing speed or the image quality, to generate the output image.

12. The apparatus according to claim 2, wherein the output image generating unit selects either the image restored by the restoration unit or the image color-converted by the second color converting unit in accordance with system resource situations of the apparatus, to generate the output image.

13. The apparatus according to claim 1, wherein: the block pallet conversion unit changes the number of the pallet colors in accordance with the processing mode.

14. An image processing method for performing color conversion processing on an input image, the method comprising: converting the input image in units of blocks into (i) pallet color information including pallet colors number of which is less than pixels included in one of the blocks and (ii) selection information used to select one of the pallet colors for each pixel;performing first color conversion on the pallet color information; andselecting for each pixel, based on the selection information, one of the pallet colors of the pallet color information on which the first color conversion is performed, to restore an image.

15. The method according to claim 14, further comprising: performing second color conversion on the input image; andgenerating an output image based on at least one of the restored image and the image subjected to the second color conversion.

16. The method according to claim 15, further comprising: extracting an edge from the input image and performing adaptive filtering on the input image, wherein:the second color conversion is performed on the filtered image.

17. The method according to claim 15, further comprising: judging an attribute of each region of the input image, wherein:the generating of the output image comprises selecting for each region either the restored image or the image subjected to the second color conversion in accordance with the judged attribute of the corresponding region.

18. The method according to claim 17, wherein: the input image is data written in printer description language, andthe judging of the attribute of each region comprises interpreting the data written in the printer description language to judge the attribute of each region.

19. The method according to claim 17, wherein: the selecting of either the restored image or the image subjected to the second color conversion comprises: selecting the image subjected to the second color conversion for a region, which a result of the judging indicates as a text/line-drawing region, andselecting the restored image for a region, which the result of the judging indicates as a photograph region.

20. The method according to claim 15, wherein the selecting of either the restored image or the image subjected to the second color conversion comprises selecting either the image restored or the image subjected to the second color conversion in accordance with a processing mode.

21. The method according to claim 15, wherein the selecting of either the restored image or the image subjected to the second color conversion comprises selecting either the restored image or the image subjected to the second color conversion in accordance with a document mode.

22. The method according to claim 15, wherein the selecting of either the restored image or the image subjected to the second color conversion comprises selecting either the restored image or the image subjected to the second color conversion in accordance with a color mode.

23. The method according to claim 16, wherein: the generating of the output image comprises selecting either the restored image or the image subjected to the second color conversion in accordance with a color mode, andthe selecting selects the image, which is subjected to the adaptive filtering and not subjected to the second color conversion if the color mode is a black-and-white mode.

24. The method according to claim 15, wherein the generating of the output image comprises selecting either the restored image or the image subjected to the second color conversion in accordance with a processing speed mode of an apparatus which performs the color conversion processing, the processing speed mode indicating whether priority is attached to the processing speed or the image quality.

25. The method according to claim 15, wherein the generating of the output image comprises selecting either the restored image or the image subjected to the second color conversion in accordance with a system resource situations of an apparatus, which performs the conversion processing.

26. The method according to claim 19, further comprising: changes the number of the pallet colors in accordance with the processing mode.

27. A computer readable medium storing a program causing a computer to execute a process for performing color conversion processing on an input image, the process comprising: converting the input image in units of blocks into (i) pallet color information including pallet colors number of which is less than pixels included in one of the blocks and (ii) selection information used to select one of the pallet colors for each pixel;performing first color conversion on the pallet color information; andselecting for each pixel, based on the selection information, one of the pallet colors of the pallet color information on which the first color conversion is performed, to restore an image.

28. A computer data signal embodied in a carrier wave for enabling a computer to perform color conversion processing on an input image, the process comprising: converting the input image in units of blocks into (i) pallet color information including pallet colors number of which is less than pixels included in one of the blocks and (ii) selection information used to select one of the pallet colors for each pixel;performing first color conversion on the pallet color information; andselecting for each pixel, based on the selection information, one of the pallet colors of the pallet color information on which the first color conversion is performed, to restore an image.