An improved algorithm for fractal image encoding based on relative error

The fractal image coding algorithm is a kind of brand-new coding algorithm, which uses the self-similarity of the image to realize the image data´s compression. But for each range block, searching out the best matched domain block is a extremely time-consuming thing. A faster encoding algorithm is thus proposed in this paper. The proposed algorithm uses an inequality linking the root-mean-square(RMS) and the relative error, sets up a kick-out condition based on the relative error to avoid the excessive searching, and thus the remaining domain blocks could be discarded, so its runtime is significantly shortened. The simulation results on 2 test images with different complexities demonstrate that the proposed scheme could averagely achieve the speed- up of 32 times as the baseline fractal algorithm with full searching, while it gives an insignificant degradation in the subjective quality of the decoded image.