Adaptive wavelet transforms with spatially varying filters for scalable image coding
An adaptive wavelet transform algorithm for scalable image coding is proposed. A quadtree segmentation scheme based on an entropy criterion is proposed to segment the image into several regions to allow for adaptive filtering using different types of prototype wavelet filters. A joint bit allocation and coding method is presented to efficiently code the segmented image in an embedding fashion. Experimental results show that the proposed scheme generally provides higher peak signal-to-noise ratios (PSNRs) at higher bit rates, and significantly better visual quality at lower bit rates, compared to fixed-filter wavelet transform based coding schemes.