System and method for image compression and decompression

• US 20020006229A1
• Filed: 11/30/2000
• Published: 01/17/2002
• Est. Priority Date: 03/11/1997
• Status: Active Grant

• Current Assignee: Upload Technologies S.A.
• Original Assignee: Computer and Information Sciences, Inc.
• Inventors: Fisher, Paul S., Fisher, Howard P., Chao, Hongyang, Hua, Zeyi
• Granted Patent: US 6,904,175 B2
• Time in Patent Office: Days
• US Class Current: 382/240
• CPC Class Codes: H04N 19/102 characterised by the element, parameter or selection affected or controlled by the adaptive coding
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets

Abstract

A wavelet-based image compression system and method are presented. Compression is accomplished by performing a wavelet transformation of an input digital image. The resulting wavelet coefficients are compared to a threshold value. Coefficients falling below the threshold are discarded. The remaining coefficients are quantized. The quantized coefficients are then compressed using an entropy encoding technique, such as arithmetic, run length, or Huffman encoding, or a combination of Huffman and run length encoding. The wavelet transform can be an integer wavelet transform derived using a lifting scheme or correction method, while the quantization scheme can be sub-band oriented. Input color image pixels can be reduced using a color table. In addition, color pixels can be transformed between color spaces prior to wavelet transformation.

Claims

1. A method for compressing an image, comprising the steps of:

performing a wavelet transformation of the image;

quantizing the wavelet transformed image;

applying entropy coding to the quantized image; and

outputting a file that includes the entropy coded image.

2. The method of claim 1, further comprising the following step:

performing a color transformation of the image.

3. The method of claim 1, further comprising the following step:

performing the wavelet transformation using an integer wavelet transform.

4. The method of claim 3, further comprising:

deriving the integer wavelet transform using a lifting scheme.

5. The method of claim 3, further comprising:

deriving the integer wavelet transform using a correction method.

6. The method of claim 1, wherein the step of quantizing includes the sub-step of:

processing the wavelet transformed image using sub-band oriented quantization.

7. The method of claim 1, further comprising:

comparing the wavelet transformed image to at least one predetermined threshold value.

8. A method for wavelet-based image compression using reduced color components, comprising the steps of:

creating a color table for an input image having a plurality of pixels;

calculating an index for each of the pixels, whereby generating a plurality of indices;

performing a wavelet transformation on the indices;

applying entropy coding on the transformed indices; and

outputting a file that includes the entropy coded indices.

9. The method of claim 8, further comprising:

dithering the pixels to generate the indices.

10. The method of claim 8, further comprising:

partitioning a large image into a plurality of small images to produce the input image.

11. The method of claim 10, wherein the large image is selectively partitioned.

12. An image processing system, comprising:

means for performing a wavelet transformation on an input image;

means for quantizing the wavelet transformed image;

means for entropy coding to the quantized image; and

means for outputting the entropy coded image.

13. The image processing system of claim 12, further comprising:

means for receiving the entropy coded image;

means for entropy decoding the received image;

means for de-quantizing the decoded image; and

means for performing an inverse wavelet transformation on the de-quantized image to produce an output image.

14. The image processing system of claim 12, further comprising:

means for displaying the output image.

15. The image processing system of claim 12, further comprising:

means for transmitting the entropy encoded image over a communications medium.

16. An image compression system, comprising:

a compressor configured to generate a compressed image based on an integer wavelet transform derived using a technique selected from a lifting scheme and a correction method.

17. The image compression system of claim 16, wherein the compressor quantizes a wavelet transformed image to produce the compressed image.

18. The image compression system of claim 16, wherein the compressor entropy encodes a quantized image to produce the compressed image.

19. The image compression system of claim 16, wherein the compressor performs a color transformation to produce the compressed image.

20. An image decompression system, comprising:

a decompressor configured to generate a decompressed image based on an integer inverse wavelet transform derived using a technique selected from a lifting scheme and a correction method.

21. A computer-readable memory storing a computer program for directing a computer system to perform image compression, wherein the computer program implements steps for performing a wavelet transformation of an input image, quantizing the wavelet transformed image, applying entropy coding to the quantized image, and outputting a file that includes the entropy coded image.

22. A method of compressing a data file, comprising the steps of:

performing a wavelet transformation of the data file to provide a series of wavelet coefficients;

quantizing those wavelet coefficients which fall above a predetermined threshold value to provide a quantized series of wavelet coefficients; and

compressing the quantized series of wavelet coefficients to provide a compressed data file.

23. The method of claim 22 wherein the compressing step comprises the step of applying an entropy coding to the quantized series of wavelet coefficients.

24. The method of claim 23 wherein the entropy coding is selected from the group of arithmetic, Huffman, run length and Huffman run length combined.

25. The method of claim 23 further comprising the step of performing a color transformation of the data file prior to the wavelet transformation step.

26. The method of claim 25 wherein the quantizing step comprises sub-band orientation quantization.

27. The method of claim 26 wherein the wavelet transformation step comprises integer wavelet transformation.

28. The method of claim 22 further comprising the step of filtering the data file prior to the wavelet transformation step.

29. The method of claim 27 wherein the integer wavelet transformation comprises biorthogonal filter method.

30. The method of claim 27 wherein the integer wavelet transformation comprises the correction method.

31. A compressed data file comprising a wavelet transformation of a data file having a series of compressed, quantized wavelet coefficients, the quantized wavelet coefficients having a value above a predetermined threshold value to provide a quantized series of wavelet coefficients.

32. A program for compressing a data file comprising:

a routine for performing a wavelet transformation of the data file to provide a series of wavelet coefficients;

a routine for quantizing those wavelet coefficients which fall above a predetermined threshold value to provide a quantized series of wavelet coefficients; and

a routine for compressing the quantized series of wavelet coefficients to provide a compressed data file.