Blocking Effect Reduction Based on Human Visual System for Highly Compressed Images

When a high compression ratio is required, the block discrete cosine transform (BDCT) decoded image suffers from the blocking effect: boundaries between adjacent image blocks visible for low bit rates. A blocking effect reduction algorithm in DCT domain is proposed to reduce blocking artifacts as many as possible, while preserving edge information. In this paper, the model of blocking artifacts is built, a convenient edge detection measurement is introduced and the characteristic of human visual system (HVS) is sufficiently utilized. A visibility function of blocking artifacts is proposed based on the activity masking and brightness masking properties of HVS. The blocks which visibility of the blocking artifacts is less than the threshold do not need any processing. For smooth regions, the parameter that affects blocking artifacts is modified and the step blocks are replaced with linear blocks. For texture regions, the DCT-domain post-filtering method is applied to reduce blocking effect. Experimental results show the proposed algorithm can significantly reduce blocking artifacts while preserving edge and texture information