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Predictive Grayscale Image Coding Scheme Using VQ and BTC

Predictive Grayscale Image Coding Scheme Using VQ and BTC. Author: Yu-Chen Hu Source: Fundamenta Informaticae 78 (2007) 239–255 Speaker: Meng -Jing Tsai Date: 2011.12.29. Outline. Introduction The proposed scheme Block prediction technique Vector quantization (VQ)

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Predictive Grayscale Image Coding Scheme Using VQ and BTC

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  1. Predictive Grayscale Image Coding Scheme Using VQ and BTC Author: Yu-Chen Hu Source: FundamentaInformaticae 78 (2007) 239–255 Speaker: Meng-Jing Tsai Date: 2011.12.29

  2. Outline • Introduction • The proposed scheme • Block prediction technique • Vector quantization (VQ) • Block truncation coding (BTC) • Conclusion

  3. Introduction • A predictive image compression scheme that combines the advantages of vector quantization and moment preserving block truncation coding to provide good image quality at a low bit rate.

  4. VQ is widely used because it has a simple decoding structure and requires a low bit rate. However, a lot of computational costs are needed in the codebook design procedure and the image coding procedure. • BTC has the advantages of requiring very low computational cost and providing good • reconstructed image quality. However, a high bitrate is needed in BTC.

  5. To reduce the bit rate

  6. Vector quantization (VQ) image vector : x=(x1,x2,…,xk) d(x,y1) d(x,y2) … … d(x,yN) Codebook Original image index of ymin

  7. 0 1 2 Image vector (21,44,45,78) 253 254 255 VQ encoding procedure • Find Closest codeword Codebook (12,14,13,16) (20,25,17,11) Index (24,45,47,76) 2 (78,22,77,20) (33,32,97,98) (20,55,53,26)

  8. VQ encoding procedure w h Image Index table Index table

  9. VQ decoding procedure w h Image Index table Index table

  10. Block truncation coding (BTC) • 區塊臨界值=區塊平均值

  11. ≤

  12. Block prediction technique

  13. ≤

  14. ≤ ≤

  15. BTC

  16. ≤

  17. Experimental results of image quality of related BTC scheme and VQ with different codebook sizes

  18. Results of block prediction technique for BTC and VQ with different search range sr

  19. Conclusion • This scheme exploitsthe block similarities among neighboring image blocks to improve the bit rate of traditional hybrid methods based on VQ and BTC. • By choosing adequate controllingthresholds, the proposed scheme provides good image quality at a low bitrate.

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