Modified EZW coding for the M-band wavelet transform and its application to image compression

This paper describes the extension of the embedded zero wavelet tree coding technique (J.M. Shapiro, 1993) to the M-band wavelet transform. Through this scheme, we improve the efficiency of the embedded zero wavelet tree coding, that finds extensive application as a variable bit-rate coder. To prove the efficacy, we compare the compression ratio and the PSNR obtained by a traditional 2-band wavelet based coder, with those obtained with the M-band wavelet based EZW coder. One additional point discussed in this paper, is the performance of a traditional 2-level quantization in EZW against an M-adaptive coder. We see the advantages and disadvantages in going in for an M-adaptive coder and conclude based on the PSNR and compression ratio obtained at various bit-rates. The variable bit-rate is emulated as multiple scans. Hence graphs plot the compression ratio or the PSNR against the number of scans. An important inference drawn from this paper is that, M-band wavelet transform with M=Odd, exhibits special properties, as a result of which the EZW scheme performs much more efficiently with them