A New Image Coding Technique with Low Entropy Using a Flexible Zerotree

概要

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A zerotree image-coding scheme is introduced that effectively exploits the inter-scale self-similarities found in the octave decomposition by a wavelet transform. A zerotree is usuful for efficiently coding wavelet coefficients ; its efficiency was proved by Shapiro's EZW. In the EZW coder, wavelet coefficients are sympolized, then entropy-coded for further compression. In this paper, we analyze the symbols produced by the EZW coder and discuss the entropy for a symbol. We modify the procedure used for symbol-stream generation to produce lower entropy. First, we modify the fixed relation between a parent and children used in the EZW coder to raise the propability that a significant parent has significant children. The modified relation is flexibly modified again based on the observation that a significant coefficient is more likely to have significant coefficients in its neighborhood. The three relations are compared in terms of the number of symbols they produce.
社団法人電子情報通信学会の論文
1998-12-25