1. 1 Vladimir Botchko botchko@lut.fi Lecture 6. Image Compression Lappeenranta University of Technology (Finland)

2. 2 Image Compression n Lossy and lossless compression n Fundamentals n Fidelity Criteria n Image Compression Models n Error Free Compression n Lossy Compression n Compression Standards n Video Image Compression

3. 3 Fundamentals n Coding redundancy n Interpixel Redundancy n Psychovisual Redundancy

4. 4 Image Compression n Lossy and lossless compression n Fundamentals n Fidelity Criteria n Image Compression Models n Error Free Compression n Lossy Compression

5. 5 Image Compression n Lossy and lossless compression n Fundamentals n Fidelity Criteria n Image Compression Models n Error Free Compression n Lossy Compression

6. 6 Error Free Compression n Variable-length coding n Huffman coding n Near optimal variable length codes n Lossless predictive coding

7. 7 One-dimensional predictive coding n Right histogram is a Laplacian pdf

8. 8 Image Compression n Lossy and lossless compression n Fundamentals n Fidelity Criteria n Image Compression Models n Error Free Compression n Lossy Compression

9. 9 Lossy Compression n Delta Modulation DM n Differential pulse code modulation DPCM n Transform coding

10. 10 Lossy Compression n Delta Modulation DM n Differential pulse code modulation DPCM n Transform coding

11. 11 Transform Coding n Transform basis functions n Fourier transform n Walsh-Hadamard transform n Discrete cosine transform n Wavelet transform

12. 12 Transform Coding n ON-LINE DEMO on the course Web page n (browser with Java 2): n References: n Dmitry Kolesnikov: n Introduction n Lecture

13. 13 Walsh-Hadamard transform Walsh-Hadamard basis images: one – black, minus one – white.

14. 14 Transform Coding n Transform basis functions n Fourier transform FT n Walsh-Hadamard transform WHT n Discrete cosine transform DCT n Wavelet transform WT

15. 15 DCT n Image udersampling (upper row), DCT (lower row)

16. 16 Transform Coding n Transform basis functions n Fourier transform n Walsh-Hadamard transform n Discrete cosine transform n Wavelet transform

17. 17 Haar transform Haar basis images: positive-black, negative-white, zero-gray

18. 18 Wavelet Transform (1 level decomposition)

19. 19 Wavelet Transform (2 level decomposition)

20. 20 Wavelet transform n Wavelets (upper row), image undersampling (lower row), compare with DCT

21. 21 Image Compression n Lossy and lossless compression n Fundamentals n Fidelity Criteria n Image Compression Models n Error Free Compression n Lossy Compression n Compression Standards n Video image compression

22. 22 Video image compression n A moving image sequence 192 kB/frame (left), intra (independetly inside frame) frame compression 6 kB/frame (center), inter (by subtraction of frames) frame compression 512 bytes/frame and intra compression is also kept (right). n MPEG format.

23. 23 Gray-scale image compression. Fractals. nfnf