FAST FRACTAL IMAGE COMPRESSION USING PYRAMIDS

Fractal image compression is based on the self-similarity search of th e image. The encoding process is computationally intensive. We present a fast fractal image encoding algorithm that is based on a refinement of the fractal code from an initial coarse level of a pyramid. Assumi ng that the distribution of the matching error is described by an inde pendent, identically distributed (i.i.d.) Laplacian random process, we derive the threshold sequence for the objective function in each pyra midal level. The algorithm is quasi-optimal in terms of minimizing the mean square error. Computational efficiency depends on the depth of t he pyramid and the search step size, and could be improved by up to tw o orders of magnitude over the computational effort required for a ful l search of the original image. (C) 1998 Society of Photo-Optical Inst rumentation Engineers. [S0091-3286(98)01306-3].