Method and system for adaptive color and contrast for display devices

• US 20050035974A1
• Filed: 05/18/2004
• Published: 02/17/2005
• Est. Priority Date: 07/10/2002
• Status: Active Grant

• Current Assignee: Gamehancement LLC (Jeffrey M. Gross)
• Original Assignee: Genesis Microchip Inc. (STMicroelectronics NV)
• Inventors: Nair, Hari N., Agrawal, Neha, Neema, Ashish, Choudhary, Saif, Johary, Arun
• Granted Patent: US 7,034,843 B2
• Time in Patent Office: Days
• US Class Current: 345/589
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 5/06 using colour palettes, e.g. look-up tables

Abstract

Automatically and adaptively controlling contrast and color of a display device by computing a normalized histogram of a current image, computing degrees of correlation between the normalized histogram and a number of template histograms, sorting the template histograms based upon the associated degrees of correlation, selecting a number of the best correlated template histograms based on the sorting, blending the selected the transfer functions associated with the selected template histograms to form a blended transfer function, and applying the blended transfer function to the current image.

Claims

1. A method for automatically and adaptively controlling contrast and color of a display device, comprising:

computing a normalized histogram of a current image;

computing degrees of correlation between the normalized histogram and a number of template histograms;

sorting the template histograms based upon the associated degrees of correlation;

selecting a number of the best correlated template histograms based on the sorting;

blending the selected the transfer functions associated with the selected template histograms to form a blended transfer function; and

applying the blended transfer function to the current image.

2. The method of claim 1, wherein the current image is a video frame V_n. included in a video formed of a number L video frames.

3. The method as recited in claim 2, further comprising:

applying the blended transfer function to video frames V_n+l to video frame V_n+k.

4. The method of claim 3, further comprising:

averaging the normalized histogram with a previous number M normalized histograms each of which is associated with a particular video frame.

5. The method of claim 1, further comprising:

if none of the degrees of correlation is greater than a predetermined threshold value, then applying only a default transfer function to the current image.

6. The method of claim 1, wherein the histogram is normalized to a predefined range.

7. The method of claim 1, further comprising:

analyzing the pixel luma distribution, by collection and analysis of pixel luma distribution using multiple bands; and

generating a luma and a chroma control response.

8. The method of claim 7 in which the multiple bands include overlapping bands.

9. The method of claim 8 that collects pixel luma distribution information using bin counters for each band.

10. The method of claim 9 in which the collection of pixel luma distribution information is limited to a user-definable region in the display.

11. The method of claim 10 in which the application of automatic and adaptive contrast and color control is to a user-definable region in the display.

12. The method of claim 10 in which an optimal contrast control response is generated by analysis of the actual luma distribution followed by blending of user defined contrast control responses.

13. The method as recited in claim 1, wherein the computing a degree of correlation between the normalized histogram and a template histogram comprises:

determining an absolute difference of the heights of each bin of the template histogram and the normalized histogram; and

adding the absolute differences together.

14. The method as recited in claim 13, wherein the best correlation is the lowest value of the adding.

15. The method of claim 1 in which RGB, YUV, YCrCb, YPrPb or any other color domain are utilized.

16. The method of claim 15 in which analog or digital displays are utilized.

17. The method of claim 2 wherein the histogram for a particular frame is stored in a memory.

18. Computer program product for automatically and adaptively controlling contrast and color of a display device, comprising:

computer code for computing a normalized histogram of a current image;

computer code for computing degrees of correlation between the normalized histogram and a number of template histograms;

computer code for sorting the template histograms based upon the associated degrees of correlation;

computer code for selecting a number of the best correlated template histograms based on the sorting;

computer code for blending the selected the transfer functions associated with the selected template histograms to form a blended transfer function;

computer code for applying the blended transfer function to the current image; and

computer readable medium for storing the computer code.

19. The computer program product of claim 18, wherein the current image is a video frame V_n. included in a video formed of a number L video frames.

20. The computer program product as recited in claim 19, further comprising:

computer code for applying the blended transfer function to video frames V_n+1 to video frame V_n+k.

21. The computer program product of claim 20, further comprising:

computer code for averaging the normalized histogram with a previous number M normalized histograms each of which is associated with a particular video frame.

22. The computer program product of claim 18, further comprising:

computer code for applying only a default transfer function to the current image if none of the degrees of correlation is greater than a predetermined threshold value.

23. The computer program product of claim 18, wherein the histogram is normalized to a predefined range.

24. The computer program product of claim 18, further comprising:

computer code for analyzing the pixel luma distribution, by collection and analysis of pixel luma distribution using multiple bands; and

computer code for generating a luma and a chroma control response.

25. The computer program product of claim 24 in which the multiple bands include overlapping bands.

26. The computer program product of claim 25 that collects pixel luma distribution information using bin counters for each band.

27. The computer program product of claim 26 in which the collection of pixel luma distribution information is limited to a user-definable region in the display.

28. The computer program product of claim 27 in which the application of automatic and adaptive contrast and color control is to a user-definable region in the display.

29. The computer program product of claim 27 in which an optimal contrast control response is generated by analysis of the actual luma distribution followed by blending of user defined contrast control responses.

30. The computer program product as recited in claim 18, wherein the computing a degree of correlation between the normalized histogram and a template histogram comprises:

computer code for determining an absolute difference of the heights of each bin of the template histogram and the normalized histogram; and

computer code for adding the absolute differences together.

31. The computer program product as recited in claim 30, wherein the best correlation is the lowest value of the adding.

32. The computer program product of claim 18 in which RGB, YUV, YCrCb, YPrPb or any other color domain are utilized.

33. The computer program product of claim 32 in which analog or digital displays are utilized.

34. The computer program product of claim 19 wherein the histogram for a particular frame is stored in a memory.

35. An apparatus for automatically and adaptively controlling contrast and color of a display device, comprising:

means for computing a normalized histogram of a current image;

means for computing degrees of correlation between the normalized histogram and a number of template histograms;

means for sorting the template histograms based upon the associated degrees of correlation;

means for selecting a number of the best correlated template histograms based on the sorting;

means for blending the selected the transfer functions associated with the selected template histograms to form a blended transfer function; and

means for applying the blended transfer function to the current image.

36. A system for adaptive color contrast of an image displayed on a display device, comprising

a controlling state machine adapted to receive a vertical data enable signal and an input luma signal;

a memory block coupled to the controlling state machine adapted to receive input luma and provides an output luma;

a creation of histogram block coupled to and controlled by the state machine;

a histogram average block coupled to and controlled by the state machine;

a template weight calculator block coupled to and controlled by the state machine;

a template transfer function black coupled to and controlled by the state machine;

a snapping function block coupled to and controlled by the state machine that provides final blended transfer function to the memory; and

adaptive chroma correction block coupled to and controlled by the state machine adapted to receive the output and the input chroma provide a final output chroma, wherein collection of a current image histogram is performed during an active frame wherein when a vertical inactive period (blanking) starts, the histogram is averaged, if necessary, with previous image histograms and the template transfer function weights are calculated and the template transfer functions are blended using these weights and the snapping operation is performed on the blended output to recover the full dynamic range and a new contrast transfer function is written to a luma LUT memory that is used for the next image frame.