关键词: 块效应, 块离散余弦变换, 后处理, 自适应平滑

Abstract: A major drawback related to the block-based discrete transform (BDCT) for image compression is that the decoded images, especially at very low bit rates, exhibit highly noticeable discontinuities at the boundaries of blocks, namely blocking artifacts. In this paper, a novel adaptive de-blocking algorithm is proposed to reduce blocking artifacts. Blocking artifacts are modeled as step function in our paper, then the image blocks are divided into three categories. They are smooth blocks, texture blocks, edge blocks. For smooth blocks, the expression of amplitude of blocking artifacts is educed firstly in our algorithm, then the adaptive smooth filter according to amplitude of blocking artifacts and the smooth degree function is proposed to reduce blocking artifacts. For the texture blocks and edge blocks, the Sigma filter is used to smooth the block boundaries in our algorithm. The experiment results show that the proposed algorithm reduces the blocking artifacts effectively and preserves the original edges faithfully.

Key words: Blocking Artifacts, Block discrete cosine transform, Post-processing, Adaptive smoothing