Fast hierarchical codebook search for fractal coding of still images

This paper presents a method for fast encoding of still images based on iterated function systems (IFSs). The major disadvantage of this coding approach, usually referred to as fractal coding, is the high computational effort of the encoding process compared to e.g. the JPEG algorithm [1]. This is mainly due to the costly “full search” of the transform parameters within a fractal codebook. We therefore propose an hierarchical encoding scheme which is based upon a two level codebook search and a structural classification of its entries. By this way only a small subset of the codebook has to be considered, which increases encoding speed significantly. Refining the initial codebook and applying a second search even increases the reconstruction quality compared to the full search but with a fraction of its computational effort.