Color gamut mapping/enhancement technique using skin color detection

• US 20080166044A1
• Filed: 08/27/2007
• Published: 07/10/2008
• Est. Priority Date: 01/09/2007
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J., Pan, Hao
• Granted Patent: US 8,050,496 B2
• Time in Patent Office: Days
• US Class Current: 382/167
• CPC Class Codes: G06V 10/56 relating to colour
• CPC Class Codes: H04N 1/62 Retouching, i.e. modification of isolated colours only or in isolated picture areas only
• CPC Class Codes: H04N 1/628 Memory colours, e.g. skin or sky

Abstract

A method for mapping/enhancing the color of an image to be displayed on a display includes receiving an image having a plurality of pixels where each of the pixels has a plurality of color components. The image is processed using a pair of gamut color mapping operations in combination with skin-tone pixels detection to modify the image in a suitable manner for presentation on the display, wherein the technique includes color temperature compensation.

Claims

1. A method for modifying an image to be displayed on a display comprising:

(a) receiving an image calibrated to a first color gamut generally smaller than the color gamut of said display;

(b) filtering said image with a spatial filter to define regions including generally skin-tones in such a manner that the skin-tone regions of the image are modified in a manner different than generally non-skin-tone regions of said image are modified when displayed on said display;

(c) modifying a color temperature of said filtered image;

(d) displaying said color temperature modified filtered image on said display.

2. The method of claim 1 wherein said filtering does not change the color temperature of said received image.

3. A method for modifying an image to be displayed on a display comprising:

(a) receiving an image calibrated to a first color gamut generally smaller than the color gamut of said display;

(b) modifying a color temperature of said received image;

(c) filtering said color temperature modified image with a filter that varies based upon said modified color temperature to define pixels including generally skin-tones in such a manner that the skin-tone pixels of the image are modified in a manner different than generally non-skin-tone pixels of said image are modified when displayed on said display;

(d) displaying said filtered image on said display.

4. A method for modifying an image to be displayed on a display comprising:

(a) receiving an image calibrated to a first color gamut generally smaller than the color gamut of said display;

(b) modifying a color temperature of said received image;

(c) filtering said color temperature modified image with a spatial filter to define regions including generally skin-tones in such a manner that the skin-tone regions of the image are modified in a manner different than generally non-skin-tone regions of said image are modified when displayed on said display;

(d) displaying said filtered image on said display.

5. The method of claim 4 wherein said filtering of said skin-tone regions varies based upon said color temperature of said modified image.

6. The method of claim 4 wherein said filtering of said non-skin-tone regions varies based upon said color temperature of said modified image.

7. The method of claim 4 wherein said skin-tone regions are defined by a spatial low pass filter.

8. The method of claim 4 wherein said filtered image includes edges.

9. The method of claim 4 wherein said filtered image is defined using a edge preserving low pass filter.

10. The method of claim 4 wherein said spatial filter includes a region defined around a pixel of interest.

11. The method of claim 10 wherein said spatial filter determines pixels within said region that are sufficiently similar to said pixel of interest.

12. The method of claim 4 wherein said filtering includes a look-up table to further define said skin-tone regions.

13. The method of claim 4 wherein said filtering includes a spatial characteristics that determines whether proximate pixels have said skin-tones.

14. The method of claim 4 wherein said filtering includes a color space characteristic that determines if proximate pixels have said skin-tones.

15. The method of claim 4 wherein said image is separated into a base image and a residual image, said base image is said filtered and said residual image includes said higher frequency content.

16. The method of claim 4 wherein said lower frequency content is separated by edges.

17. The method of claim 4 wherein said higher frequency content includes high frequency details, noise, and artifacts.

18. The method of claim 4 wherein said filter includes a threshold.

19. The method of claim 4 wherein said threshold is based upon the content of said image.

20. The method of claim 4 wherein said filtering includes

(a) modifying said image with a first gamut mapping to a first color gamut;

(b) modifying said image with a second gamut mapping to a second color gamut, wherein said second color gamut is generally different than said first color gamut;

(c) determining potential skin-tone pixels of said image;

(d) modifying said image based upon said first gamut mapping, said second gamut mapping, and said potential skin-tone pixels.

21. The method of claim 20 wherein said first gamut mapping leaves said image substantially unchanged.

22. The method of claim 20 wherein said second gamut mapping substantially changes said image to match that of an input image calibration.

23. The method of claim 20 wherein said second color gamut is generally larger than said first color gamut.

24. The method of claim 20 wherein said potential skin-tone pixels are filtered with a color spatial filter.

25. The method of claim 20 wherein said first gamut mapping is independent of skin-tones.

26. The method of claim 20 wherein said second gamut mapping is independent of skin-tones.

27. The method of claim 20 wherein the values associated with said potential skin-tone pixels are non-binary.

28. The method of claim 20 wherein said potential skin-tone pixels may be modified based upon a gain.

29. The method of claim 20 wherein said potential skin-tone pixels are color temperature adjusted.

30. The method of claim 29 wherein said color temperature adjustment is based upon the said modified color temperature.

31. The method of claim 20 wherein said first gamut mapping is adjusted in a manner that distinguishes between generally skin tones and generally at least one of generally white and generally neutral color.

32. A method for modifying an image to be displayed on a display comprising:

(a) receiving an image calibrated to a first color gamut generally smaller than the color gamut of said display;

(b) modifying a color temperature of said received image;

(c) filtering said received image with a filter to define pixels including generally skin-tones in such a manner that the skin-tone pixels of the image are modified in a manner different than generally non-skin-tone pixels of said image are modified when displayed on said display, wherein said filtering is also performed in such a manner that said skin-tone pixels and said non-skin tone pixels are filtered in a different manner that accounts for color temperature;

(d) displaying said filtered image on said display.

33. The method of claim 32 wherein said filtering is based upon said color temperature modified image.

34. The method of claim 32 wherein said modifying is based upon said filtered image.

35. The method of claim 32 wherein said color temperature filtering adjusts the hue of the displayed image.

36. The method of claim 32 wherein said color temperature filtering distinguishes skin tones from at least one of whites and neutrals.