Enhanced histogram equalization

• US 8,698,961 B2
• Filed: 07/14/2011
• Issued: 04/15/2014
• Est. Priority Date: 05/21/2010
• Status: Active Grant

• Current Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Original Assignee: VIXS Systems Incorporated (Pixelworks Incorporated)
• Inventors: Astrachan, Paul M.
• Primary Examiner(s): YENKE, BRIAN P
• Application Number:
  US13/182,801
• Publication Number:
  US 20110285913A1
• Time in Patent Office: 1,006 Days
• Field of Search: 348/672, 382/168
• US Class Current: 348/672
• CPC Class Codes: H04N 21/4318 by altering the content in the rendering process, e.g. blanking, blurring or masking an image region image enhancement or restoration in general G06T5/00
• CPC Class Codes: H04N 21/44008 involving operations for analysing video streams, e.g. detecting features or characteristics in the video stream arrangements characterised by components specially adapted for monitoring, identification or recognition of video in broadcast systems H04H60/59
• CPC Class Codes: H04N 5/57 Control of contrast or brightness

Abstract

A video processor includes a video stream translation module configured to generate a translated luminance value for a pixel of a current frame of a video data stream. The translated luminance value is based on a first luminance value for the pixel and a first translation matrix for the current frame of the video data stream. The video processor includes a filter configured to generate an output luminance value for the pixel based on the translated luminance value and a target translated luminance value for the pixel. The output luminance value may be based on a weighted average of the translated luminance value and the target translated luminance value using a first weighting factor. The video processor may include a first weighting factor generator configured to generate the first weighting factor based on luminance values of the current frame of the video stream.

Claims

1. An apparatus comprising:

a histogram generator configured to receive luminance values of a current frame of a video data stream and configured to generate a histogram of the luminance values;

a translation matrix generator configured to receive the luminance values and the histogram and configured to generate a first translation matrix for the current frame of the video data stream;

a video stream translation module configured to receive the luminance values and the first translation matrix and configured to generate a translated luminance value for a pixel of the current frame of the video data stream, the translated luminance value being based on a first luminance value for the pixel of the luminance values and the first translation matrix;

a first weighting factor generator configured to receive the luminance values and configured to generate a first weighting factor;

a target pixel generator configured to receive the luminance values and configured to generate a target translated luminance value for the pixel based on a target translation matrix and the first luminance value; and

a filter configured to receive the translated luminance value, the first weighting factor, and the target translated luminance value, and configured to generate an output luminance value for the pixel based on the translated luminance value, and the target translated luminance value.

2. The apparatus, as recited in claim 1, wherein the output luminance value is based on a weighted average of the translated luminance value and the target translated luminance value using the first weighting factor.

3. The apparatus, as recited in claim 1, wherein the first weighting factor is proportional to an average luminance of the current frame of the video data stream.

4. The apparatus, as recited in claim 1, wherein the target translation matrix is a linear function.

5. The apparatus, as recited in claim 1, wherein the target translation matrix is a non-linear function.

6. The apparatus, as recited in claim 1,

wherein the translation matrix generator is configured to generate the first translation matrix based on a second translation matrix for the current frame of the video data stream, a prior first translation matrix for a prior frame of data, and a weighting factor.

7. The apparatus, as recited in claim 6, further comprising:

a weighting factor generator configured to generate the weighting factor based on luminance values of the current frame of the video data stream.

8. The apparatus, as recited in claim 7, wherein the weighting factor is a weight of the second translation matrix and the weighting factor is proportional to an average luminance of the current frame of the video data stream.

9. The method, as recited in claim 1, wherein the target translation matrix implements an S-curve function that concentrates luminance values within particular luminance bins.

10. A method comprising:

generating a histogram of luminance values of a current frame of a video data stream;

generating a first translation matrix for the current frame of the video data stream using the histogram and the luminance values;

generating a translated luminance value for a pixel of the current frame of the video data stream, the translated luminance value being generated using a first luminance value for the pixel of the luminance values and the first translation matrix;

generating a first weighting factor using the luminance values;

generating a target translated luminance value for the pixel using a target translation matrix and the first luminance value; and

generating an output luminance value for the pixel based on the translated luminance value, the target translated luminance value for the pixel, and the first weighting factor.

11. The method, as recited in claim 10, wherein the output luminance value is based on a weighted average of the translated luminance value and the target translated luminance value using the first weighting factor.

12. The method, as recited in claim 11, further comprising:

updating the first weighting factor based on luminance values of the current frame of the video stream.

13. The method, as recited in claim 12, wherein the first weighting factor is proportional to an average luminance of the current frame of the video data stream.

14. The method, as recited in claim 10, wherein the target translation matrix is a linear function of the luminance values.

15. The method, as recited in claim 10, wherein the target translation matrix is a non-linear function of the luminance values.

16. The method, as recited in claim 10, further comprising:

generating the first translation matrix based on a second translation matrix for the current frame of the video data stream, a prior first translation matrix for a prior frame of data, and a weighting factor.

17. The method, as recited in claim 16, further comprising:

generating the weighting factor based on luminance values of the current frame of the video stream.

18. The method, as recited in claim 17, wherein the weighting factor is a weight of the second translation matrix and the weighting factor is proportional to an average luminance of the current frame of the video data stream.