Abstract: The DRDC method has been improved in this paper.8 isometry transforms are added into the calculation of difference matrix of domain blocks and range blocks.The affine transform parameters，produced from the calculation of difference matrix，were used to calculate fractal codes corresponding to range blocks and a set of inference for formula was given.The relationship between 8 isometry transforms matrix and its corresponding invert matrix was given and the calculation of fractal codes was simplified.The improved method，which is used to calculate the distance between difference matrix of domain blocks and range blocks，was proposed.The proposed algorithm is compared with global searching method and DRDC method in the experiments.The results show that the speed can be improved greatly with the ensurance of the decoded image quality by using the proposed algorithm.

Key words: fractal coding, difference matrix, global searching, fractal codes

摘要： 对DRDC方法进行了改进，在定义域块与值域块的差值矩阵计算中，增加了8种旋转变换，并利用求解差值矩阵过程中产生的仿射变换参数来计算值域块所对应的分形码，并给出公式推导。此外，还给出了8种旋转变换矩阵与其对应逆矩阵的关系，从而进一步简化分形码求解。还对值域块与定义域块的差值矩阵间距离计算提出了改进措施。在实验中，将该文算法分别同全局搜索法、DRDC法进行了比较，结果表明，该文算法能在基本保证解码图像质量的同时，大大提高编码速度。

关键词: 分形编码, 差值矩阵, 全局搜索, 分形码