Hybrid gamut mapping

• US 7,379,208 B2
• Filed: 05/06/2004
• Issued: 05/27/2008
• Est. Priority Date: 05/06/2004
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Henley, Sharon A., Sloan, Rocklin J.
• Primary Examiner(s): Lee; Thomas D.
• Assistant Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US10/842,029
• Publication Number:
  US 20050248785A1
• Time in Patent Office: 1,482 Days
• Field of Search: 358/1.9, 358/2.1, 358/500, 358/504, 358517-518, 358/527, 382/162, 382166-167
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

In converting a color in a source gamut to a color in a destination gamut, selection of a conversion technique is determined for the source color based on the hue aspect of the source color, a maximum chroma of the destination gamut associated with the source color'"'"'s hue aspect, and the lightness value of the source color relative to a lightness value associated with the maximum chroma. In converting a set of colors such as in a digital color image, selection of a conversion technique is performed for each color in the color image, independent of the color aspects of, and/or the conversion technique selected for, neighboring colors.

Claims

1. For use with a computing system, a method of converting a source color having lightness, chroma and hue aspects from a source gamut to a destination gamut comprising:

identifying a maximum chroma of the destination gamut for the hue of the source color; and

selecting one conversion from a plurality of conversions based on a lightness value associated with the maximum chroma of the destination gamut and the lightness value associated with the source color.

2. A method according to claim 1, wherein the selected conversion comprises a single gamut mapping algorithm (GMA).

3. A method according to claim 2, wherein the GMA converts the source color by clipping only the chroma of the source color.

4. A method according to claim 1, wherein the selected conversion comprises a combination of two or more GMAs.

5. A method according to claim 4, wherein the combination comprises an average of the results obtained by the two or more GMAs.

6. A method according to claim 5, wherein the two or more GMAs comprise a first GMA which converts the source color by clipping only the chroma of the source color and a second GMA which converts the source color to a destination color of the destination gamut which shares the same hue and results in a minimum color difference between the source and destination colors.

7. A method according to claim 5, further comprising:

determining whether the average represents a color which is outside the destination gamut; and

performing another conversion if it is determined that the colorfalls outside the destination gamut.

8. A method according to claim 7, wherein the other conversion comprises one or more of the GMAs in the combination.

9. A method according to claim 8, wherein the other conversion converts the source color to a destination color of the destination gamut which shares the same hue and results in a minimum color difference between the source and destination colors.

10. A method according to claim 1, further comprising:

scaling lightness values of the source and destination gamuts such that a minimum lightness value of the source gamut is coincident with a minimum lightness value of the destination gamut and a maximum lightness value of the source gamut is coincident with a maximum lightness value of the destination.

11. A method according to claim 10, wherein the scaling is a linear scaling.

12. A computer-readable memory medium in which computer-executable process steps are stored, the process steps for use with a computing system to convert a source color having lightness, chroma and hue aspects from a source gamut to a destination gamut, wherein the process steps implement a method according any of claims 1 to 11.