Abstract
In this paper, we present a new scheme to compress still grayscale images based on iterated function system (IFS) employing a quadtree partitioning structure with adaptive threshold. In the conventional fractal image compression based on quadtree partitioning, the distortion tolerance between levels is prefixed, so the encoding processing cannot adapt to the given image. In our approach, the threshold between levels is set according to the features of current range block. Thus, the encoding processing can make good use of the natural characteristics of the input image and adapt to them in partitioning. Computer simulation shows that the adaptive threshold (AT) IFS is more adaptive than the conventional IFS encoding scheme, and it is more convenient in practice.