Sub-study Of The Shape Coding Algorithm

The paper mainly studies the algorithm of fractal image compression, then introduces and implements a new algorithm of image compression: fractal image coding based on wavelet.Firstly, the theory of fractal and the common algorithm of fractal image compression is presented. Secondly, we studied the fractal coding parameters. Based on the study of 8 geometry transforms, the result shows that the transforms are not an intrinsic part of fractal image coding. We can increase the domain blocks directly to enlarge the search pools. It may replace the search pools of 8 geometry transforms. There is not an effective method to compress the parameter g, because the distribution of it is fairly random. So we adopt the mean of range block as the parameter of fractal coding to replace the g. With the mean of range block, the compression ratio is improved, the coding time and reconstruction time are decreased. Then we discuss the relations among range blocks covariance, contrast scaling s and MSE. The analysis shows why a better reconstruction image is obtained when the range of contrast scaling s is larger than one.　 Finally, an algorithm of characteristic value is given based on the convergence characteristics of fractal image coding and the effect of different values of contrast scaling s. Experimental results show that the coding time is decreased obviously.