| Image is very important medium at application of multimedia. Because of limitation of transmission bandwidth and storage capacity, image compression became one of critical techniques at information transmission system. In recent decade, wavelet transform has been studied and applied extensively because of its good time-frequency features and tally with human visual system. In this paper, we focus on the wavelet transform code. Firstly, We summarize the basic theory on image code, including some familiar compression techniques and some international compression standards on image and video. Secondly, we introduce the basic theory on wavelet transform code. At last, a improved image compression algorithm is put forword about still images based on embedded wavelet zero-tree coding scheme. First of all, image is divided into some multi-resolution subband images by using wavelet transform. The low-frequency subband is coded with lossless entropy coding. The high-frequency subband are made edge detection. Different edge,grain and smooth area use different coding schemes. Compared with original embedded zero-tree wavelet algorithm, this improved coding algorithm can apply the wavelet transform coefficient effectively, low bit-ratio and intensify the visual effective of restruction imges synchronously. The results of experiment show that the reconstruction images are good, and the peak signal-to-noise ratio(PSNR) of the reconstruction images are improved greatly at the same bit-ratio. Furthermore this paper combined the EZW with fractal coding method, analysed the fractal coding algorithm based on wavelet transform.
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