MERGED QUADTREE FRACTAL IMAGE COMPRESSION

The quadtree method is usually used in fractal block coding, but its e fficiency is very low. We propose a new scheme, merged quadtree partit ioning (MQP), for efficient image compression. It is an improved quadt ree method, and can merge the quadtree nodes on the same level and on the different levels to share one transformation. As the merged nodes describe irregular regions with boundaries approximating the image edg es, which need only one transformation, the total number of transforma tions required by MQP is much less than by the quadtree method. Thus, we obtain a greater compression ratio. In addition, we speed up MQP me thod by using the relationship between the search of the merged range and that of its parent range, and obtain a shorter encoding time than with other partitioning schemes. (C) 1998 Society of Photo-Optical Ins trumentation Engineers.