In order to improve the speed of fractal image coding algorithm

this paper proved an inequality linking the root-mean-square(RMS) and similar measure mathematically and set up two kick-out conditions based on the similar measure and standard deviation of matched block.Therefore it can search out the best-matched block to a range block with a reduced search space at encoding process

which can shorten its runtime significantly.Computer simulation on 4 test images with different complexities demonstrate that the proposed scheme could speedup the coding process

while the subjective quality of the decoded image has a little degradation than that using the corresponding baseline fractal coding algorithm.