Fast fractal image compression algorithm using specific update search

The fractal image compression (FIC) algorithm is difficult to be widely used in real-time applications due to the huge consumption of its encoding time. Inspired by the fact that in the decoding process, for any original image, a fixed point is generated by the iterations of the fractal codes, the authors propose a specific update search FIC (SUSFIC) algorithm, which uses a scale number to control the update times of the fractal codes and to find acceptable matching domain blocks rather than the best ones in the selected domain blocks pool. To further reduce the computation time, in their proposed algorithm, the image blocks created by the equidistant sampling in the range of the original blocks are used to replace themselves when calculating the correlation coefficients as the distances between the adjacent domain blocks. The experimental results presented show that their proposed SUSFIC algorithm has a significant improvement in encoding time under the premise of setting an appropriate search update threshold and maintaining image quality when compared with the state-of-the-art FIC algorithms. Therefore, it is a better FIC algorithm.