Color gamut mapping/enhancement technique using skin color detection

• US 20080166042A1
• Filed: 03/29/2007
• 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 7,933,445 B2
• Time in Patent Office: Days
• US Class Current: 382/164
• 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.

Claims

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

(a) receiving an image having 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) displaying said filtered image on said display.

2. The method of claim 1 wherein said skin-tone regions are defined by a spatial low pass filter.

3. The method of claim 1 wherein said filtered image includes edges.

4. The method of claim 1 wherein said filtered image is defined using a edge preserving low pass filter.

5. The method of claim 1 wherein said spatial filter includes a region defined around a pixel of interest.

6. The method of claim 5 wherein said spatial filter determines pixels within said region that are sufficiently similar to said pixel of interest.

7. The method of claim 1 wherein said filtering includes a look-up table to further define said skin-tone regions.

8. The method of claim 1 wherein said filtering includes a spatial characteristics that determines whether proximate pixels have said skin-tones.

9. The method of claim 1 wherein said filtering includes a color space characteristic that determines if proximate pixels have said skin-tones.

10. The method of claim 1 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.

11. The method of claim 1 wherein said lower frequency content is separated by edges.

12. The method of claim 1 wherein said higher frequency content includes high frequency details, noise, and artifacts.

13. The method of claim 1 wherein said filter includes a threshold.

14. The method of claim 1 wherein said threshold is based upon the content of said image.

15. A method for enhancing the color of an image to be displayed on a display comprising:

(a) receiving an image having a plurality of pixels where each of said pixels has a plurality of color components;

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

(c) 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;

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

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

16. The method of claim 15 wherein said first gamut mapping leaves said image substantially unchanged.

17. The method of claim 15 wherein said second gamut mapping substantially changes said image to match that of an input image calibration.

18. The method of claim 15 wherein said second color gamut is generally larger than said first color gamut.

19. The method of claim 15 wherein said potential skin-tone pixels are filtered with a color space filter.

20. The method of claim 15 wherein said first gamut mapping is independent of skin-tones.

21. The method of claim 15 wherein said second gamut mapping is independent of skin-tones.

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

23. The method of claim 15 wherein the values associated with said potential skin-tone pixels are non-binary.

24. The method of claim 15 wherein said potential skin-tone pixels may be modified based upon a gain.

25. The method of claim 24 wherein said gain is user adjustable.

26. The method of claim 15 wherein said potential skin-tone pixels may be modified based upon a hue.

27. The method of claim 26 wherein said hue is user adjustable.

28. The method of claim 15 wherein said potential skin-tone pixels may be based upon saturation.

29. The method of claim 28 wherein said saturation is user adjustable.

30. The method of claim 15 wherein said skin-tone pixels are based upon two dimensional look up tables.

31. The method of claim 15 wherein said skin-tone pixels are also based upon one dimensional look up tables.

32. The method of claim 15 wherein the image is divided into 6 regions of a color space.

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

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

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

(c) displaying said filtered image on said display once displayed.

34. The method of claim 33 wherein said skin-tone pixels are defined by a spatial low pass filter.

35. The method of claim 34 wherein said filtering includes a look-up table to further define said skin-tone pixels.

36. The method of claim 35 wherein said filtering includes a spatial characteristics that determines whether proximate pixels have said skin-tones.

37. The method of claim 36 wherein said filtering includes a color space characteristic that determines if proximate pixels have said skin-tones.

38. A method for enhancing the color of an image to be displayed on a display comprising:

(a) receiving an image having a plurality of pixels where each of said pixels has a plurality of color components;

(b) selectively modifying a pixel of said image with either a first gamut mapping to a first color gamut or a second gamut mapping to a second color gamut, wherein said second color gamut is generally different than said first color gamut, based upon the likelihood that said pixel is a skin-tone pixel of said image.

39. The method of claim 38 wherein said first gamut mapping leaves said pixel substantially unchanged once displayed.

40. The method of claim 39 wherein said skin-tone pixel is filtered with a spatial filter.

41. The method of claim 38 wherein said first gamut mapping is independent of skin-tones.

42. The method of claim 41wherein said second gamut mapping is independent of skin-tones.

43. The method of claim 38 wherein said skin-tone pixel may be modified based upon a gain.

44. The method of claim 43 wherein said gain is user adjustable.

45. The method of claim 38 wherein said skin-tone pixel may be modified based upon a hue.

46. The method of claim 45 wherein said hue is user adjustable.

47. The method of claim 38 wherein said skin-tone pixel may be based upon saturation.

48. The method of claim 47 wherein said saturation is user adjustable.