TEXTURE MIXING VIA UNIVERSAL SIMULATION By Gustavo Brown

A framework for studying texture in general, and for texture mixing in particular, is presented in this paper. The work follows concepts from universal type classes and universal simulation. Based on the well-known Lempel and Ziv (LZ) universal compression scheme, the universal type class of a one dimensional sequence is defined as the set of possible sequences of the same length which produce the same dictionary (or parsing tree) with the classical LZ incremental parsing algorithm. Universal simulation is realized by sampling uniformly from the universal type class, which can be efficiently implemented. Starting with a source texture image, we use universal simulation to synthesize new textures that have, asymptotically, the same statistics of any order as the source texture, yet have as much uncertainty as possible, in the sense that they are sampled from the broadest pool of possible sequences that comply with the statistical constraint. When considering two or more textures, a parsing tree is constructed for each one, and samples from the trees are randomly interleaved according to pre-defined proportions, thus obtaining a mixed texture. As with single texture synthesis, the k-th order statistics of this mixture, for any k, asymptotically approach the weighted mixture of the k-th order statistics of each individual texture used in the mixing. We present the underlying principles of universal types, universal simulation, and their extensions and application to mixing two or more textures with pre-defined proportions.