An efficient image compression method based on SPIHT algorithm using run-length coding

EZW (Embedded Zerotree Wavelets) coding algorithm has not only high compression rate but also some new features such as progressive coding/decoding, low computational complexity, etc. Based on EZW, many improved algorithms have been developed in recent years. SPIHT (Set Partitioning in Hierarchical Trees) is an outstanding one among them. Statistical experiments show that some directional and positional dependencies still exist between significant coefficients in each subband. Based on this structural characteristic, this paper incorporated RLC(Run-length Coding) into SPIHT and proposed a new scanning scheme to cluster significant coefficients’ 1-D distribution, which reduced coefficients’ such structural redundancy to the largest extent. Theoretic analysis and experiments indicate: after introducing RLC into SPIHT, not only is the low computational complexity preserved, but also increases the PSNR up to 2 dB at very high compression ratios, and the average improvement is about 0.1dB at 0.3-0.7bpp for standard test images used. The visual quality of reconstructed images is also significantly improved.