Method and apparatus for block based image compression with multiple non-uniform block encodings

• US 8,326,053 B2
• Filed: 06/16/2009
• Issued: 12/04/2012
• Est. Priority Date: 02/13/2003
• Status: Active Grant

• Current Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Original Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Inventors: Iourcha, Konstantine, Pomianowski, Andrew S. C., Koduri, Raja
• Primary Examiner(s): Do, Anh Hong
• Application Number:
  US12/485,537
• Publication Number:
  US 20090274366A1
• Time in Patent Office: 1,267 Days
• Field of Search: 382/164, 382/166, 382/232, 382/243, 382/224, 382/233, 382/100, 382/294, 725/146, 341/50, 341/67, 341/50.67, 375/E7.176, 375/E7.265, 358/466
• US Class Current: 382/232
• CPC Class Codes: G06T 15/04 Texture mapping
• CPC Class Codes: H04N 19/96 Tree coding, e.g. quad-tree coding

Abstract

A method and apparatus provides for block based image compression with multiple non-uniform block encodings. In one embodiment, an image is divided into blocks of pixels. In one embodiment the blocks are four pixels by four pixels, but other block sizes are used in other embodiments. In one embodiment, a block of pixels in the original image is compressed using two different methods to produce a first and second compressed block. Thus, each block in the original image is represented by two, typically different, compressed blocks. In one embodiment, color associated with a pixel is determined by combining the compressed information about the pixel in the first compressed block with information about the pixel in the second compressed block. In another embodiment, global information about the image is combined with the information in the first and second compressed blocks.

Claims

1. A method adapted for use in an image compression apparatus to compress an input image comprising a plurality of pixels, the method comprising:

partitioning said input image into a plurality of original blocks, each comprising a selected subset of the pixels comprising said input image;

decomposing each of said original blocks to generate a respective one of a plurality of decomposed blocks;

compressing each of said decomposed blocks to generate a respective one of a plurality of compressed blocks; and

combining all of said plurality of compressed blocks to generate an output image;

wherein said decomposing further comprises;

applying a function to an original value of each of said pixels comprising each of said original blocks to obtain a decomposed value selected to reduce the amount of space needed to encode said original value; and

wherein compressing each of said plurality of decomposed blocks comprises the steps of;

determining a best fit curve for said decomposed values;

storing two end point values selected on said best fit curve; and

storing an index value for each of said pixels in said decomposed block wherein each of said index values comprises a respective one of a plurality of points selected on said best fit curve.

2. The method of claim 1 wherein said best fit curve is a straight line.

3. The method of claim 2 wherein each of said end point values comprises 8 bits.

4. The method of claim 3 wherein each of said index values comprises a selected interpolated value on said best fit curve between said end points.

5. The method of claim 4 wherein each of said index values comprises 3 bits.

6. The method of claim 5 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

7. The method of claim 6 wherein said vector is of unit length.

8. The method of claim 2 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

9. The method of claim 8 wherein said vector is of unit length.

10. The method of claim 1 wherein each of said index values comprises a selected interpolated value on said best fit curve between said end points.

11. The method of claim 10 wherein each of said index values comprises 3 bits.

12. The method of claim 11 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

13. The method of claim 12 wherein said vector is of unit length.

14. The method of claim 1 wherein each of said end point values comprises 8 bits.

15. The method of claim 14 wherein each of said index values comprises 3 bits.

16. The method of claim 15 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

17. The method of claim 16 wherein said vector is of unit length.

18. The method of claim 1 wherein each of said index values comprises 3 bits.

19. The method of claim 1 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

20. The method of claim 19 wherein said vector is of unit length.

40. The method of claim 19 wherein said vector is of unit length.

21. A method adapted for use in an image compression apparatus to compress an input image comprising a plurality of pixels, the method comprising:

partitioning said input image into a plurality of original blocks, each comprising a selected subset of the pixels comprising said input image;

decomposing each of said original blocks to generate a respective one of a plurality of decomposed blocks by applying a function to an original value of each of said pixels comprising each of said original blocks to obtain a decomposed value selected to reduce the amount of space needed to encode said original value;

compressing each of said decomposed blocks to generate a respective one of a plurality of compressed blocks by;

determining a best fit curve for said decomposed values;

storing two end point values selected on said best fit curve;

storing an index value for each of said pixels in said decomposed block wherein each of said index values comprises a respective one of a plurality of points selected on said best fit curve; and

combining all of said plurality of compressed blocks to generate an output image.

22. The method of claim 21 wherein said best fit curve is a straight line.

23. The method of claim 22 wherein each of said end point values comprises 8 bits.

24. The method of claim 23 wherein each of said index values comprises a selected interpolated value on said best fit curve between said end points.

25. The method of claim 24 wherein each of said index values comprises 3 bits.

26. The method of claim 25 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

27. The method of claim 26 wherein said vector is of unit length.

28. The method of claim 22 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

29. The method of claim 28 wherein said vector is of unit length.

30. The method of claim 21 wherein each of said index values comprises a selected interpolated value on said best fit curve between said end points.

31. The method of claim 30 wherein each of said index values comprises 3 bits.

32. The method of claim 31 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

33. The method of claim 32 wherein said vector is of unit length.

34. The method of claim 21 wherein each of said end point values comprises 8 bits.

35. The method of claim 34 wherein each of said index values comprises 3 bits.

36. The method of claim 35 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

37. The method of claim 36 wherein said vector is of unit length.

38. The method of claim 21 wherein each of said index values comprises 3 bits.

39. The method of claim 21 wherein each of said index values comprises a vector that represents the axis of the function stored in the compressed block.

41. An image compression system comprising:

a storage medium that stores computer readable code;

one or more processors, operative to execute the computer readable code and in response, operative to;

partition said input image into a plurality of original blocks, each comprising a selected subset of the pixels comprising said input image;

decompose each of said original blocks to generate a respective one of a plurality of decomposed blocks;

compress each of said decomposed blocks to generate a respective one of a plurality of compressed blocks; and

combine all of said plurality of compressed blocks to generate an output image;

wherein said decomposing further comprises;

applying a function to an original value of each of said pixels comprising each of said original blocks to obtain a decomposed value selected to reduce the amount of space needed to encode said original value; and

wherein compressing each of said plurality of decomposed blocks comprises the steps of;

determining a best fit curve for said decomposed values;

storing two end point values selected on said best fit curve; and

storing an index value for each of said pixels in said decomposed block wherein each of said index values comprises a respective one of a plurality of points selected on said best fit curve.

42. An image compression system comprising:

a storage medium that stores computer readable code;

one or more processors, operative to execute the computer readable code and in response, operative to;

partition said input image into a plurality of original blocks, each comprising a selected subset of the pixels comprising said input image;

decompose each of said original blocks to generate a respective one of a plurality of decomposed blocks by applying a function to an original value of each of said pixels comprising each of said original blocks to obtain a decomposed value selected to reduce the amount of space needed to encode said original value;

compress each of said decomposed blocks to generate a respective one of a plurality of compressed blocks by;

determining a best fit curve for said decomposed values;

storing two end point values selected on said best fit curve;

storing an index value for each of said pixels in said decomposed block wherein each of said index values comprises a respective one of a plurality of points selected on said best fit curve; and

combining all of said plurality of compressed blocks to generate an output image.

43. An image compression system comprising:

logic operative to compress an image block by generating;

a first portion representing a vector;

a second portion representing color points; and

a third portion representing indices to map to colors generated from or represented by said second portion.

44. The system of claim 43 wherein said first portion represents a vector of unit length.

45. The system of claim 43 wherein said first portion represents a vector of non-unit length.

46. The system of claim 43 wherein said vector represents a vector on a hemisphere.

47. A computer readable medium storing non-transitory code that when executed by one or more processors causes the one of more processors to compress an image block by generating:

a first portion representing a vector;

a second portion representing color points; and

a third portion representing indices to map to colors generated from or represented by said second portion.

48. An image compression system comprising:

logic operative to compress an image block by generating;

a first data portion representing first and second endpoints;

a second data portion representing indices, said indices mapping pixel values to values derived from said first and second endpoints;

and wherein said first and second endpoints represent vectors relative to a surface.

49. The system of claim 48 wherein a first block portion of data for representing said image comprises said first and second data portions.

50. The system of claim 49 further comprising a second block portion of data for representing said image, said second block portion comprising:

a third data portion representing third and fourth endpoints;

a fourth data portion representing indices, said indices mapping pixel values to values derived from said third and fourth endpoints; and

wherein said third and fourth endpoints represent color values.

51. The system of claim 50 wherein an original block of said image are represented by at least said first and second block portions.

52. A method performed by an image compression apparatus, the method comprising:

generating a first data portion representing first and second endpoints;

generating a second data portion representing indices, said indices mapping pixel values to values derived from said first and second endpoint; and

wherein said first and second endpoints represent vectors relative to a surface.

53. The method of claim 52 comprising generating a first block portion of data for representing said image comprising said and first and second data portions.

54. The method of claim 53 further comprising generating a second block portion of data for representing said image, comprising generating said second block portion to comprise:

a third data portion representing third and fourth endpoints;

a fourth data portion representing indices, said indices mapping pixel values to values derived from said third and fourth endpoints; and

wherein said third and fourth endpoints represent color values.

55. The method of claim 54 comprising representing an original block of said image by at least said first and second block portions.