中文摘要：

提出一种基于分块的图像编码方向自适应提升小波变换（DA-LWT），在每级变换中采用固定的方向块大小，仅保留一、二级变换所产生的方向信息，更高级别的方向由其前两级预测获得，从而减少边信息的开销．根据图像块的最小预测残差能量自适应选择滤波器的滤波方向，有效消除图像相邻像素间的冗余，降低高频系数能量．采用基于分数像素插值方案，提高方向分辨率．实验表明，DA-LwT的变换系数具有更好的“零树”特性，可取得比传统提升小波变换更好的编码效率和视觉效果．

英文摘要：

A direction-adaptive lifting wavelet transform （DA-LWT） based on block of image is proposed in this＇paper. The fixed size of directional block is used for each level of transform. Directional information is retained by the first and second level transform. The direction of higher level transform is obtained by the prediction of the first two levels, and the cost of side information is reduced. According to the minimum prediction residual energy, the filtering direction of filter is selected adaptively to eliminate the redundancy between neighboring pixels effectively and reduce the energy of high-frequency coefficients. Adopting the interpolation based on fractional pixel, and the direction resolution is improved. Experimental results show that the transform coefficients of image obtained by DA-LWT have a better ＂ zero-tree＂ feature. DA-LWT can obtain better coding efficiency and visual effects compared with traditional lifting wavelet transform.