An edge-preserving image coding system with vector quantization

SUMMARY Image coding with vector quantization (VQ) reveals several defects which include edge degradation and high encoding complexity. This paper presents an edge-preserving coding system based on VQ to overcome these defects. A signal processing unit first classifies image blocks into low-activity or high-activity class. A high-activity block is then decomposed into a smoothing factor, a bit-plane and a smoother (lower variance) block. These outputs can be more efficiently encoded by VQ with lower distortion. A set of visual patterns is used to encode the bit-planes by binary vector quantization. We also develop a modified search-order coding to further reduce the redundancy of quantization indexes. Simulation results show that the proposed algorithm achieves much better perceptual quality with higher compression ratio and significant lower computational complexity, as compared to the direct VQ.