1. Burrows Wheeler Transform In Image Compression
Markus Gärtner
David Havelin
Classroom Presentation
1st December 2000

2. Overview Project Goals Burrows Wheeler Transform (BWT)
Application of the BWT:
Lossless Compression
Lossy Compression
Performance
Conclusion
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

3. Project Goals
Implementation of an efficient Burrows-Wheeler Transform (BWT) algorithm
Implementation of coding scheme for transformed data
Analysis of lossless compression performance
Possible combinations of BWT with Subband Coding schemes
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

4. Burrows-Wheeler Transform
Lossless Reversible Block-Sorting Algorithm
Input: ABDACA 1 A B D C 2 3 4 5 6
Output: CADAAB
I=2
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

5. Lossless Compression
BWT
Move-to
Front
Entropy 1D
Image
Original
MTF
MTF/BWT
JPEG-LS
Peppers
7.5925
6.9449
5.5727
4.513
Lena
7.4451
6.6973
5.4819
4.237
Bridge
5.7056
5.1756
4.7974
5.500
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

6. Subband Coding Wavelet Transform Q Run- length BWT MTF Entropy
Wavelet-BWT 1D
DCT Q
Run-
length
BWT
MTF
Entropy
DCT-BWT
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

7. PSNR vs. Rate for image “peppers.tif”
Subband Coding - DCT
PSNR vs. Rate for image “peppers.tif”
JPEG quantization
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

8. Subband Coding - Wavelets
PSNR vs. Rate for image “peppers.tif”
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000

9. Conclusions Image compression with BWT possible Limitations
Lack of scalability
Performance of Said-Pearlman hard to reach
Possibilities for improvement
Sophisticated scanning techniques (Peano)
Run-length Encoder
Optimized Quantization
Markus Gärtner, David Havelin: Burrows Wheeler Transform
Stanford University, 1st December 2000