Adaptive Post-Processing for Fractal Image Compression

Fractal image compression is a block based technique. The blocks of the underlying image partition are called range blocks. Like all block based techniques, fractal coding suffers from blocking artifacts, in particular at high compression ratios. Moreover, due to the recursive nature of the fractal decoder blocking artifacts also show up in the interior of the range blocks. This paper proposes an effective post-processing to reduce both kinds of these artifacts. We apply a smoothing filter adapted to the partition before each iteration of the decoding process which reduces the blocking artifacts in the interior of the range blocks. After decoding the reconstructed image is enhanced by applying another adaptive filter along the range block boundaries. This filter is designed to reduce blocking artifacts while maintaining edges and texture of the original image. The experimental results show that the artifacts are reduced and significant improvements can be achieved. Our method compares favourably with previously published post-processing techniques for fractal image compression.