Zerotree design for image compression: Toward weighted universal zerotree coding

We consider the problem of optimal, data-dependent zerotree design far use in weighted universal zerotree codes for image compression. A weighted universal zerotree fade (WUZC) is a data compression system that replaces the single, data-independent zerotree of Said and Pearlman with an optimal collection of zerotrees for good image coding performance across a wide variety of possible sources. We briefly describe the weighted universal zerotree encoding and design algorithms but focus primarily on the problem of optimal, data-dependent zerotree design. We demonstrate the performance of the proposed algorithm by comparing, at a variety of target rates, the performance of a Said-Pearlman style code using the standard zerotree to the performance of the same code using a zerotree designed with our algorithm. The comparison is made without entropy coding. The proposed zerotree design algorithm achieves, on a collection of combined text and gray-scale images, up to 4 dB performance improvement over a Said-Pearlman zerotree.