1. JPEG - JPEG2000 Isabelle Marque JPEGJPEG2000

2. JPEG Joint Photographic Experts Group Committe created in 1986 by: International Organization for Standardization (ISO) and International Telecommunication Union (ITU) A working group which creates the standard for still image compression

3. JPEG - JPEG2000 Two different standards Major differences : JPEGJPEG2000 Created for natural imagery Discrete Cosine Transform algorithm Created for computer generated imagery Discrete Wavelet Transform algorithm

4. JPEG Architecture of standard Forward transform Quantization Entropy coding  DC coefficient  AC coefficients Entropy encoding Source image data Forward transform Quantization Compressed image data

5. JPEG Forward transform 1. Level shifted 2. Divided into blocks of 8*8 pixels 3. Forward DCT: Entropy encoding Source image data Forward transform Quantization Compressed image data

6. JPEG DCT basis functions

7. JPEG Original image

8. JPEG DCT coefficients

9. JPEG Quantization  Quantization table  Zigzag scan Entropy encoding Source image data Forward transform Quantization Compressed image data

10. JPEG Quantization table

11. JPEG Labels after quantization

12. JPEG Entropy encoding DC coefficient and AC coefficients are coded differently DC coefficient  Encode the difference  Huffman code unmanageable  First bits to define the category and other bits to define the element in the category CategoryPossible values 0 0 1 -1 1 2 -3 -2 2 3 3-7 -6 -5 -4 4 5 6 7 Entropy encoding Source image data Forward transform Quantization Compressed image data

13. JPEG AC coefficients Defined by a certain number of terms:  Category C that a non zero label falls in  Z: number of zero since the last non zero label  Z/C points to a specific code  Follows by bits to define the element in the category  +1 code  EOB stands for End Of Block: A code after the last non zero value

14. JPEG Sample table for obtaining the huffman code Z/CCodewordZ/CCodeword 0/0 (EOB)1010 0/1001/11100 0/2011/211011 0/31001/31111001 0/410111/4111110110 0/5110101/511111110110

15. JPEG Reconstructed image

16. JPEG More accurate image  Increase the bit rate  Decrease quantization table elements Less accurate image  Decrease the bit rate  Increase quantization table elements Problem: Low rate image: « blockiness »

17. JPEG2000 Can be both lossless and lossy Improves image quality Uses a layered file structure :  Progressive transmission  Progressive rendering File structure flexibility:  Could use for a variety of applications Many functionalities

18. JPEG2000 Architecture of standard Forward transform Quantization Entropy coding Entropy encoding Source image data Forward transform Quantization Compressed image data

19. JPEG2000 Forward transform 1. Level shifted 2. Divided into blocks 3. Forward Discrete Wavelet Transform Entropy encoding Source image data Forward transform Quantization Compressed image data

20. JPEG2000 Details

21. JPEG2000

22. Discrete Wavelet Transform can be :  Irreversible: Daubechies 9-tap/7-tap filter  Reversible: 5-tap/3-tap filter  Any user could supply wavelet filter banks

23. JPEG2000 Quantization Dynamic range: depends on the number of bits and the choice of the wavelet Exponent Mantissa Entropy encoding Source image data Forward transform Quantization Compressed image data

24. JPEG2000 Entropy encoding Embedded Block Coding with Optimization Truncation of the embedded bit stream (EBCOT)  Each subband is divided into rectangular blocks which are coded independently called code blocks  Bitstream is organized in a succession of layers  Each layer corresponds to a certain distortion level  The quality of the reproduction is proportional to the numbers layers received Entropy encoding Source image data Forward transform Quantization Compressed image data

25. JPEG2000 Layered structure

26. JPEG - JPEG2000 - Quality At compression ratio: 43:1 JPEGJPEG2000

27. JPEG - JPEG2000 - Quality Method of picture quality measurement:PSNR Peak Signal To Noise Ratio in dB: Pixel of the image Pixel of the reconstructed image Size of the image Root Mean Squared Error

28. JPEG - JPEG2000 - Quality Comparison of PSNR values (dB) compressed colour images Bits per pixel0.1250.250.51.02.0 Lena JPEG24.4228.0231.1733.1235.15 Lena JPEG2000 28.1230.6132.9535.0537.35

29. CONCLUSION – Key points JPEG: DCT algorithm JPEG2000: DWT algorithm  Layered structure  Many functionalities For a similar quality of PSNR, JPEG2000 compresses almost twice more than JPEG

30. REFERENCES Introduction to Data Compression, K. Sayood, Morgan Kauffman, Second Edition, 2000. (Primary) A.N. Skodra, C.A. Christopoulos, T. Ebrahimi, « JPEG2000, the upcoming still image compression standard », Proceeding of the 11th Portuguese Conference on Pattern recognition, Porto, Portugal, May 11th-12th, pp. 359-366, 2000 JPEG, Official site: http://www.jpeg.orghttp://www.jpeg.org Home page of a member: http://www.etro.vub.ac.be/members/christopoulos.charilaos/welcome.html http://www.etro.vub.ac.be/members/christopoulos.charilaos/welcome.html http://www.aware.com/products/compression/j2kmaindemo.html http://www.cs.sfu.ca/CC/820/li/material/presentations/paper21.ppt http://dmsun4.bath.ac.uk/research/sar/dwt.html http://www.us.design-reuse.com/articles/article6691.html PSNR:http://www.snellwilcox.com/knowledgecenter/whitepapers/papers/picturequality_mpe g2.pdfhttp://www.snellwilcox.com/knowledgecenter/whitepapers/papers/picturequality_mpe g2.pdf Quality: http://jj2000.epfl.ch/jj_publications/papers/001.pdfhttp://jj2000.epfl.ch/jj_publications/papers/001.pdf