Image Compression Algorithm of SPIHT Based on Block-Tree

After analyzing the characteristics of images through wavelet transform,this paper proposes an improved SPIHT algorithm.Because the low-frequency coefficients hold 90% energy of image and they are very important for reconstructing the image,so they are not compressed and is transmitted directly.However the high-frequency coefficients are insignificant relatively,They arel not handled and transmitted.They will be appointed only during reconstructing the image.So,the quality of the image is improved and the compression rate is increased.Block-tree structure is proposed in this paper.The new algorithm demands less memory and its application area is expanded.