Successive coefficient refinement for embedded lossless image compression

Abstract

Summary form only given. We consider here a new approach to successive coefficient refinement which speeds up embedded image compression and decompression. Rather than sending the binary refinement symbol typical of existing embedded coders, our algorithm uses a ternary refinement symbol, allowing the encoder to tell the decoder when its current approximation of a given wavelet coefficient is exact. Thus, both encoder and decoder operate faster because they process fewer refinement symbols, yet the fundamental structure of the refinement process remains unchanged, i.e. it still represents a binary subdivision of the uncertainty interval. To implement a complete encoder, we combine the proposed refinement process with Shapiro's embedded zerotree wavelet (EZW) algorithm. Results for lossless compression are shown. Without optimization, the speed increase is between 5 and 12%; with optimization, it is between 9 and 15%.