Abstract:

In the compression algorithm of coefficient quantization in the DCT domain, as the code rate becomes lower, the quantization becomes more and more rou gh. Such defects as the block effect and ring effect show up after the image is reconstructed. A mixed algorithm which can weaken these defects is proposed in this paper. First, a method of boundary filtering is used to alleviate the chops between two neighboring DCT blocks, Then, the DCT blocks are classified into three types, and different methods are adopted according to their different characteristics. By this means, these defects are weakened with out blurring the image.

Key words: DCT transform, block effect, ring effect, block boundary filtering, median filtering