为了更有效地进行图像压缩，提出了一种新的混合域低比特率图像压缩编码算法。该算法首先对原始图像进行小波分解，并对中高频小波子带进一步实施自适应方向分解；然后根据小波系数统计特性，优化处理最低频子带系数；再结合小波分解与方向分解的特点，构造了一种扩展的空间方向树结构；最后采用SPIHT编码思想完成图像的压缩。实验结果表明，该混合域图像编码方法是一种高效的图像压缩算法，不仅其压缩效果明显优于SPIHT、WBCT等图像压缩方案（特别是在低比特率下），而且具有比较强的通用性与适应性。

In this paper, a new image coding algorithm based on DWT and Coutourlet is proposed. Firstly, the wavelet transform is applied to the original image, and the directional filter banks(DFB) are employed to middle and high frequency subbands; Then, the lowest frequency coefficients are optimized according to the wavelet coefficients statistical properties; Thirdly, the new extended spatial orientation tree are constructed; Finally, the encoding scheme is realized by the idea ofSPIHT. The experimental results show that the presented image compression scheme performs better than thatof the state-of-art image coders(SPIHT, WBCT), especially for low bit-rate and texture image.