A new image coding technique with low entropy using a flexible zerotree

A zerotree image-coding scheme is introduced that effectively exploits the inter-scale self-similarities found in the octave decomposition by a wavele t transform. A zerotree is useful for efficiently coding wavelet coefficien ts; its efficiency was proved by Shapiro's EZW. In the EZW coder, wavelet c oefficients are symbolized, then entropy-coded far further compression. In this paper, we analyze the symbols produced by the EZW coder and discuss th e entropy for a symbol. We modify the procedure used for symbol-stream gene ration to produce lower entropy. First, we modify the fixed relation betwee n a parent and children used in the EZW coder to raise the probability that a significant parent has significant children. The modified relation is fl exibly modified again based on the observation that a significant coefficie nt is more likely to have significant coefficients in its neighborhood. The three relations are compared in terms of the number of symbols they produc e.