A Multi-layer SPIHT Algorithm Based On Walsh Transform

Image is the main channel of information that people seize, but the image processing, transmission and store are limited because the image data is enormous. Then research image compress method is one of key technologies of image process and very important in the application fields, specially the progressive coding method.This thesis reviews the basic theory of wavelets and walsh analysis and the foundation of image compress firstly, then introduces wavelet image progressive compress algorithm-SPIHT(Set Partitioning in Hierarchical Trees,SPIHT)and the new development of SPIHT. This thesis import walsh transform to high frequency band to improve the effect of compression, due to walsh transform can concentrate the energy.A new algorithm—Multi-layer SPIHT based on walsh transform is presented in this paper on the basis of SPIHT. It smoothes the image first, then codes the wavelet and band walsh transformed smooth image using SPIHT algorithm with coding the lowest frequency band single, then codes the difference image of original image and reversion smooth image. The results indicate that, the improved SPIHT is better than original SPIHT.Compared with the original SPIHT, the improved SPIHT has these advantages as follows: first, smoothing the original image can increase the energy of lowest band; Second, coding the lowest band of wavelet smooth image single takes advantage of importance of the wavelet coefficients in the lowest band; Third, collecting important coefficients in the high frequency band using walsh transform can reduce bit stream that express their position. At last, coding the difference image can protect the brittle edge information in the image.At last, experiment using Matlab and the improved algorithm are made. The experimental results show that, the improved algorithm gives better results both in objective PSNR and subjective vision quality than the original SPIHT.