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Still Image Conpression JPEG & JPEG2000

Still Image Conpression JPEG & JPEG2000. Yu-Wei Chang 2003 4/18. Outline. Image Compression Background Overview of JPEG Overview of JPEG2000 Comparsion. Why Image Conpression. Why? Bandwidth Storage How Remove redundancy . Transform. Quantization. Entropy Coding. Image data.

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Still Image Conpression JPEG & JPEG2000

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  1. Still Image ConpressionJPEG & JPEG2000 Yu-Wei Chang 2003 4/18

  2. Outline • Image Compression Background • Overview of JPEG • Overview of JPEG2000 • Comparsion

  3. Why Image Conpression • Why? • Bandwidth • Storage • How • Remove redundancy

  4. Transform Quantization Entropy Coding Image data Output data Still Image Coding Flow • Most still image coding flow are similar • Transform: translate image to freq domain • Quantization: reduce unimportant data • Entropy coding: encode data according to probability of coeff 0101010…… High-> low equal important High-> low

  5. JPEG

  6. JPEG • Joint Photographic Expert Group • A generally used lossy image coding format • Allow tradeoff between compression ratio and image quality • Can achieve high compression ratio(20+) with almost invisible difference

  7. Quantization Table Coding Table Tables DCT Quantizer Entropy Coder Data Quantization Table Coding Table Tables Inverse Quantizer Data Entropy Decoder IDCT JPEG Coding/Decoding Flow

  8. JPEG-2000

  9. JPEG 2000 Features • Not only better efficiency, but also more functionality • Superior low bit-rate performance • Lossless and lossy compression • Multiple resolution • Range of interest(ROI)

  10. JPEG2000 v.s. JPEG low bit-rate performance

  11. JPEG2K - Quality Scalability • Improve decoding quality as receiving more bits:

  12. Spatial Scalability • Multi-resolution decoding from one bit-stream:

  13. ROI (range of interest)

  14. JPEG2000 EncoderBlock Diagram • Key Technologies: • Discrete Wavelet Transform (DWT) • Embedded Block Coding with Optimized Truncation (EBCOT) transform quantize coding

  15. Discrete Wavelet Transform LL2 HL2 HL1 LH2 HH2 LH1 HH1

  16. JPEG v.s. JPEG-2000

  17. JPEG2000 v.s. JPEG DCT Discrete Cosine Transform 8x8 Quantization Table Huffman Coding JPEG Transform Quantization Entropy Coding DWT Discrete Wavelet Transform Quantization for each sub-band Arithmetic Coding J2K

  18. Conclusion • JPEG2000 provides more functionality, and higher compression performance at low bit-rate • However, higher complexity, and more memory requirement.

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