Color conversion device, color conversion method and color conversion program

• US 20070279714A1
• Filed: 12/26/2006
• Published: 12/06/2007
• Est. Priority Date: 06/05/2006
• Status: Active Grant

• Current Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Xerox Company Limited (Fujifilm Holdings Corporation)
• Inventors: Higashikata, Ryosuke, Kishimoto, Yasunari, Taguchi, Tomoko, Ito, Akihiro
• Granted Patent: US 7,830,567 B2
• Time in Patent Office: Days
• US Class Current: 358/518
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

A color conversion device for color-converting an input image signal in an input color reproduction region of a source device, in a predetermined color space, by mapping the input image signal into an output color reproduction region of a destination device in the predetermined color space, comprising: a calculation portion for calculating a mapping destination in the output color reproduction region of a pre-specified characteristic point in the input color reproduction region; a correction portion for correcting the output color reproduction region such that a region including a saturation higher than the calculated mapping destination is eliminated; and a mapping portion for mapping the input image signal into the corrected output color reproduction region, is provided.

Claims

1. A color conversion device for color-converting an input image signal in an input color reproduction region of a source device, in a predetermined color space, by mapping the input image signal into an output color reproduction region of a destination device, in the predetermined color space, the device comprising:

a calculation portion for calculating a mapping destination in the output color reproduction region of a pre-specified characteristic point in the input color reproduction region;

a correction portion for correcting the output color reproduction region such that a region including a saturation higher than the calculated mapping destination is eliminated; and

a mapping portion for mapping the input image signal into the corrected output color reproduction region.

2. The color conversion device of claim 1, further comprising a setting portion setting a color gamut mapping method and a color gamut mapping parameter in accordance with a color reproduction objective selected from a plurality of color reproduction objectives,

the calculation portion calculating the mapping destination in accordance with the color gamut mapping method and color gamut mapping parameter that are set by the setting portion.

3. The color conversion device of claim 1, wherein the characteristic point includes at least one of a point of maximum saturation in the predetermined color space, with a maximum saturation of a predetermined color, and a point on a ridge line in the predetermined color space, corresponding to a gradation from a white point or a black point up to a point of maximum saturation of a predetermined color.

4. The color conversion device of claim 2, wherein the characteristic point includes at least one of a point of maximum saturation in the predetermined color space, with a maximum saturation of a predetermined color, and a point on a ridge line in the predetermined color space, corresponding to a gradation from a white point or a black point up to a point of maximum saturation of a predetermined color.

5. The color conversion device of claim 1, further comprising an acquisition portion for acquiring a request level relating to maintenance of saturation magnitude relations between before and after the mapping,

the correction portion correcting the output color reproduction region in accordance with the request level.

6. The color conversion device of claim 5, wherein the request level determines at least one of

whether or not it is necessary to maintain magnitude relations of saturations of colors in a vicinity of a point of maximum saturation in the predetermined color space, with a maximum saturation of a predetermined color, between before and after mapping, and

whether or not it is necessary to maintain magnitude relations of saturations of colors in a vicinity of a ridge line in the predetermined color space, corresponding to a gradation from a white point or a black point up to a point of maximum saturation of a predetermined color, between before and after mapping.

7. The color conversion device of claim 1, wherein the correction portion corrects the output color reproduction region by rewriting, of outer border data representing an outer border of the output color reproduction region, data of a saturation of a portion that corresponds to the region including a saturation higher than the calculated mapping destination.

8. The color conversion device of claim 1, wherein the correction portion corrects the output color reproduction region by newly generating outer border data representing an outer border of the output color reproduction region, with the region including a saturation higher than the calculated mapping destination being eliminated from the output color reproduction region.

9. A color conversion method for color-converting an input image signal in an input color reproduction region of a source device, in a predetermined color space, by mapping the input image signal into an output color reproduction region of a destination device, in the predetermined color space, the method comprising the steps of

calculating a mapping destination in the output color reproduction region of a pre-specified characteristic point in the input color reproduction region;

correcting the output color reproduction region such that a region that is adjacent to the calculated mapping destination and includes a saturation higher than that of a color of the mapping destination is eliminated; and

mapping the input image signal into the corrected output color reproduction region.

10. The color conversion method of claim 9, wherein a color gamut mapping method and a color gamut mapping parameter are set in accordance with a color reproduction objective selected from a plurality of color reproduction objectives, and the mapping destination is calculated in accordance with the color gamut mapping method and color gamut mapping parameter that have been set.

11. The color conversion method of claim 9, wherein a request level relating to maintenance of saturation magnitude relations between before and after the mapping is acquired, and the output color reproduction region is corrected in accordance with the request level.

12. The color conversion method of claim 10, wherein a request level relating to maintenance of saturation magnitude relations between before and after the mapping is acquired, and the output color reproduction region is corrected in accordance with the request level.

13. A color conversion program executable by a computer to perform processing for color-converting an input image signal in an input color reproduction region of a source device, in a predetermined color space, by mapping the input image signal into an output color reproduction region of a destination device, in the predetermined color space, the processing comprising the steps of:

calculating a mapping destination in the output color reproduction region of a pre-specified characteristic point in the input color reproduction region;

correcting the output color reproduction region such that a region that is adjacent to the calculated mapping destination and includes a saturation higher than that of a color of the mapping destination is eliminated; and

mapping the input image signal into the corrected output color reproduction region.

14. The color conversion program of claim 13, further comprising the processing of setting a color gamut mapping method and a color gamut mapping parameter in accordance with a color reproduction objective selected from a plurality of color reproduction objectives.

15. The color conversion program of claim 13, further comprising the processing of acquiring a request level relating to maintenance of saturation magnitude relations between before and after the mapping.

16. The color conversion program of claim 14, further comprising the processing of acquiring a request level relating to maintenance of saturation magnitude relations between before and after the mapping.