扩充编码符号的EZW改进算法

Improved EZW algorithm with extended coding symbol

为了提高EZW算法的性能,分析发现EZW算法主扫描编码对最高频子带中不重要系数的编码存在冗余,且当重要系数的所有子孙系数都是不重要系数时的编码存在冗余.据此提出了扩充编码符号的EZW改进算法,用最高频子带的坐标作为限制条件来减少不重要系数的编码冗余;通过扩充编码符号和赋予原始EZW算法的4个编码符号新的适用范围的方案来减小第二种编码冗余.实验结果表明,本文算法使峰值信噪比提高0.9～2.3dB,从而证实了本文改进算法的有效性.

To improve the performance of EZW algorithm, the encoding redundancy of dominant pass of embedded zerotree wavelet （EZW） algorithm is discussed in this paper. One redundancy exists in the encoding of insignificant coefficients in the subband at the highest frequency. Another redundancy oceurrs when all the descendant coefficients of one significant coefficient are insignificant. To reduce the redundancy, the improved EZW algorithm with extended coding symbol is presented. Using the coordinates of subband at the highest frequency as the limitation conditions, the first kind of redundancy is decreased. The second kind of redundancy can be reduced using the extension of coding symbol, and the new definition of four original coding symbols is given. Experiments show that the improved EZW algorithm can increase the peak signal to noise radio （PSNR） of image compression by 0. 9 -2. 3 dB, which proves the effectiveness of improved EZW algorithm.