An improved fractal image coding algorithm based on adaptive threshold for quadtree partition

ABSTRACT The image coding algorithm based on quadtree partitioning, which is presented by Yuval Fisher, has become the mainstream of fractal image compression. However, in the conventional Yuval Fisher’s theory, the threshold of distance between range blocks and domain blocks is pre-fixed mainly by experience, which does not take the practical statistical characteristics of range blocks into account for automatic valuation. Thus the coding algorithm could not adapt to various input images well, and sometimes the performances on certain images are not further optimized. To overcome this shortcoming, an improved adaptive threshold (AT) for quadtree partition is presented in this paper. Compared with the fixed threshold (FT) partition, this impr oved method could shorten coding time an d obtain higher PSNR that have been demonstrated by the experimental results. Furthermore, the decoded images get more subjective acceptances in accordance with the standard of Human Visual System (HVS). Keywords: fractal, image coding, quadtree partitioni ng, adaptive threshold, fixed threshold