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Gradient Match and Side Match Fractal Vector Quantizers for Images

Gradient Match and Side Match Fractal Vector Quantizers for Images. Source: IEEE Transaction on Image Processing, Vol. 11, No. 1, pp. 1- 9, January. 2002 Authors: Hsuan T. Chang Speaker: Chia-Lin Kao Date: 2004/04/26. Outline. FBC versus VQ

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Gradient Match and Side Match Fractal Vector Quantizers for Images

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  1. Gradient Match and Side Match Fractal Vector Quantizers for Images Source: IEEE Transaction on Image Processing, Vol. 11, No. 1, pp. 1- 9, January. 2002 Authors: Hsuan T. Chang Speaker: Chia-Lin Kao Date: 2004/04/26

  2. Outline • FBC versus VQ • Non-iterative Fractal Image Coding • SMVQ/GMVQ • Image Partition • Experimental results • Conclusions

  3. FBC versus VQ • VQ records the indexes of the codewords and FBC records the fractal code. • VQ’s codebook is predesigned and FBC’s domain blocks are extracted from the image itself. • Computational load of the FBC encoding and decoding processes is much higher the that of VQ.

  4. Non-iterative fractal block coding Generate the efficient domain pool Output the header and the fractal code image F Partition into non-overlapping range block If thevariance of the range block <= THv Code by the mean of the range block Else Find a domain block which similar to the range block

  5. Mean value: B=8 B Non-iterative fractal block coding (Generate the domain pool) image F I range block Rr I=512 I/B=64 domain block Dd (B x B) I/B Domain pool: a set of all domain blocks. mean image M

  6. Mean value: B=8 B Variance: Non-iterative fractal block coding (Encode the fractal code) I range block Rr I=512 image F Header information: 0 If thevariance of the range block <= THv Save the mean of Rras a fractal code

  7. Non-iterative fractal block coding (Encode the fractal code) Header information: 1 If thevariance of the range block > THv Find a domain block which similar to the range block The new affine transformation (新相仿轉換) ι:isometry transform D: all pixel values in a domain block μD: the mean of D μR: the mean of the correlative range block α : the contrast scaling; α ={n/4, n=1,2,3,…,8}

  8. Non-iterative fractal block coding (Encode the fractal code) ι: isometric transformation A fractal code contains: the isometric transformation(3b) ; the contrast scaling(3b) ;mean of the range block(6b) ; the position of domain block(12b)

  9. Non-iterative fractal block coding (Encode the fractal code) • The fractal code: (output) • Header information: 0010101…1 • Data information: 001011 010001000 011 100000 000000110101… mean=44 mean=68 ι :(a) α =4 mean=128 53th block

  10. Non-iterative fractal block coding (Generate the efficient domain pool) Ex:8-4+1=5 • We have (I/B-B+1)*(I/B-B+1)+1 domain blocks. (I:512; B:8) • (512/8-8+1)*(512/8-8+1)+1=(64-8+1)*(64-8+1)=3250 • Some neighboring domain blocks are similar to each other.

  11. Example: ND=225 Non-iterative fractal block coding (Generate the efficient domain pool) • Block-averaging method T: the sampling period ND: the number of domain blocks

  12. Non-iterative fractal block coding (Generate the efficient domain pool)

  13. SMVQ/GMVQ

  14. Super codebook and State codebooks • Super codebook =ι* α* Domain pool • State codebook(SC) is a subset of the super codebook. • State codebook contains N codewords sorting by the gradient match error Egm or the smallest side match error Esm.

  15. Image Partition • 4x4 • 8x8 • 8x8(parent) and 4x4(child) range blocks

  16. Ih: header, Iι: isometry type, Iμx:mean value, Iα:contrast scaling factor, IPD: domain block’s position, ISC:state codebook’ position

  17. Experimental result

  18. Non-iterative FBC block size 4x4 (Vth=25)

  19. Non-iterative FBC block size 8x8 (Vth=25)

  20. GMFVQ SMFVQ Experimental result

  21. Conclusions • Propose GMFVQ and SMFVQ for image coding saving about 10%-20% bit rate for the noniterative FBC technique. • Reconstructed image have the excellent quality with negligible blocking effects at edges. • Needing extra computations in constructing large super codebook and sorting the codewords to obtain state codebooks from the super codebook.

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