Quality-biased rate allocation for compound image coding with block classification

In this paper, we propose a novel rate allocation method for compound image coding using Quality-biased Rate-Distortion Optimization (QRDO) technique to enhance visual quality. The compound image is divided into 16 times 16 blocks, which are further classified into four types: smooth, text/graphics, continuous tone and hybrid blocks. Four carefully designed coding approaches according to different statistical features are introduced to compress them, and rate-distortion tradeoff with QRDO technique is considered to decide which approach should be used for each block. The quality of "text" regions is specially emphasized during this process by weighting blocks according to their types, which is verified by experimental results