Artifact reduction using two-mode filters for compressed images

The blocking effect is a major drawback of the DCT-based compression scheme at low bit rates. Significantly decreasing blocking effects can raise compression ratios for a particular image quality, or improve the quality with regard to the specific bit rate of compression. This work presents a scheme based on two mode filters in terms of the activity across block boundaries. For smooth regions, the strong smooth filter exploits the correlation between the neighboring blocks to reduce the discontinuity of the pixels across the boundaries. The weak smooth filter employs an edge-preserving smooth filter for texture and edge-based regions. Simulation results reveal that the proposed algorithm significantly lowers the blocking artifact, as judged by both objective and subjective measures.