Method and apparatus for adaptive contrast enhancement of image data

• US 8,285,040 B1
• Filed: 10/01/2009
• Issued: 10/09/2012
• Est. Priority Date: 12/09/2008
• Status: Expired due to Fees

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Inventors: Movshovich, Aleksandr, Ayzenberg, Oscar, Kuan, Katherine
• Primary Examiner(s): Do, Anh Hong
• Application Number:
  US12/572,040
• Time in Patent Office: 1,104 Days
• Field of Search: 382/100, 382/167, 382/170, 382/254, 382/263, 382/274, 382/286, 340/630, 356/438
• US Class Current: 382/167
• CPC Class Codes: G06T 5/009 Global, i.e. based on properties of the image as a whole applied in cameras using an electronic image sensor H04N23/80, H04N23/70
• CPC Class Codes: G06T 5/40 using histogram techniques
• CPC Class Codes: G06T 5/92 based on global image properties

Abstract

Adaptive contrast enhancement of image data is provided. In one embodiment a method for adaptive contrast enhancement includes receiving image data for a first frame, determining a pixel distribution for at least one color space component of the first frame based on luminance values of the pixels in the at least one color space and calculating an average picture level in the at least one color space based on the pixel distribution. The method additionally includes adjusting a look-up table (LUT) associated with the pixel distribution based on the average picture level, converting luminance values of the pixels in the first frame in the at least one color space based on the LUT to generate an enhanced image frame and outputting the enhanced image frame.

Claims

1. A method for adaptive contrast enhancement of image data, the method comprising the acts of:

receiving image data for a first frame;

determining, in a processor, a pixel distribution for at least one color space component of the first frame based on luminance values of the pixels in the at least one color space component;

calculating, in the processor, an average picture level in the at least one color space component based on the pixel distribution;

adjusting, in the processor, a look-up table (LUT) associated with the pixel distribution based on the average picture level;

converting, in the processor, the luminance values of the pixels in the first frame in the at least one color space component based on the LUT to generate an enhanced image frame; and

outputting the enhanced image frame to a display device.

2. The method of claim 1, wherein the pixel distribution is calculated for each color space component of the image data.

3. The method of claim 1, wherein adjusting the LUT comprises modifying a LUT curve based on at least one of the average picture level and a midpoint of the pixel distribution.

4. The method of claim 1, further comprising removing upper and lower values of the pixel distribution for calculation of at least one of the average picture level and a midpoint of the pixel distribution.

5. The method of claim 1, further comprising extending a LUT curve in at least one of a bright region and dark region of the pixel distribution.

6. The method of claim 1, further comprising detecting a scene change based on a comparison of the pixel distribution of the first frame with a pixel distribution of a second frame.

7. The method of claim 6, wherein the comparison is a Pearson correlation.

8. A device configured for adaptive contrast enhancement of image data, the device comprising:

at least one input terminal configured to receive image data for a first frame; and

a processor coupled to the input terminal, the processor configured to;

determine a pixel distribution for at least one color space component of the first frame based on luminance values in the at least one color space component;

extend a look-up table (LUT) curve in at least one of a bright region and dark region of the pixel distribution;

adjust a LUT associated with the pixel distribution based on the extended LUT curve;

convert the luminance values of the pixels in the first frame in the at least one color space component based on the adjusted LUT to generate an enhanced image frame; and

output the enhanced image frame.

9. The device of claim 8, wherein the pixel distribution is calculated for each color space component of the image data.

10. The device of claim 8, wherein the processor is further configured to adjust the LUT by modifying the LUT curve based on at least one of an average picture level and a midpoint of the pixel distribution.

11. The device of claim 8, wherein the processor is further configured to remove upper and lower values of the pixel distribution for calculation of at least one of an average picture level and a midpoint of the pixel distribution.

12. The device of claim 8, wherein the processor is further configured to calculate an average picture level in the at least one color space component based on the pixel distribution.

13. The device of claim 8, wherein the processor is further configured to detect a scene change based on a comparison of the pixel distribution of the first frame with a pixel distribution of a second frame.

14. The device of claim 13, wherein the comparison is a Pearson correlation.

15. A device configured for adaptive contrast enhancement of image data, the device comprising:

at least one input terminal configured to receive image data for a first frame; and

a processor coupled to the input terminal, the processor configured to;

determine a first pixel distribution for at least one color space component of the first frame based on luminance values of pixels in the at least one color space component;

convert luminance values of the pixels in the first frame in the at least one color space component based on a look-up table (LUT) to generate an enhanced image frame;

output the enhanced image frame;

determine a second pixel distribution for the at least one color space component of a second frame based on luminance values of pixels in the at least one color space component;

detect a scene change based on a comparison of the first and second pixel distributions; and

update the LUT based on a detected scene change.

16. The device of claim 15, wherein the first and second pixel distributions are calculated for each color space component of the first and second image frames.

17. The device of claim 15, wherein the comparison is a Pearson correlation.

18. The device of claim 15, wherein the processor is further configured to remove upper and lower values of the first pixel distribution for calculation of at least one of an average picture level and a midpoint of said pixel distribution.

19. The device of claim 15, wherein the processor is further configured to extend a LUT curve in at least one of a bright region and dark region of the first pixel distribution.

20. A device configured for adaptive contrast enhancement of image data, the device comprising:

at least one input terminal configured to receive image data for a first frame; and

a processor coupled to the input terminal, the processor configured to;

determine a pixel distribution for at least one color space component of the first frame based on luminance values of the pixels in the at least one color space;

calculate an average picture level in the at least one color space based on the pixel distribution;

adjust a look-up table (LUT) associated with the pixel distribution based on the average picture level;

convert the luminance values of the pixels in the first frame in the at least one color space based on the LUT to generate an enhanced image frame; and

output the enhanced image frame.

21. The device of claim 20, wherein the pixel distribution is calculated for each color space component of the image data.

22. The device of claim 20, wherein the processor is further configured to adjust the LUT by modifying a LUT curve based on at least one of the average picture level and a midpoint of the pixel distribution.

23. The device of claim 20, wherein the processor is further configured to remove upper and lower values of the pixel distribution for calculation of at least one of the average picture level and a midpoint of the pixel distribution.

24. The device of claim 20, wherein the processor is further configured to extend a LUT curve in at least one of a bright region and dark region of the pixel distribution.

25. The device of claim 20, wherein the processor is further configured to detect a scene change based on a comparison of the pixel distribution of the first distribution with a pixel distribution of a second frame.

26. The device of claim 25, wherein the comparison is a Pearson correlation.