The blocking effect is the major drawback in discrete cosine transform (DCT)-based codecs at low bit rates. When a high compression ratio is required, boundaries between adjacent image blocks become visible. This kind of degradation probably will affect
the judgment of an end user. In this work, a four-neighboring-block
zero-masking technique is proposed in the DCT frequency domain.
The proposed algorithm uses a shift block within four adjacent DCT
blocks to reduce computational complexity. By slightly modifying
several DCT coefficients in the shift block, the artifacts that result from quantization and dequantization processes are alleviated. The simulation results show that both visual perception and objective image quality are noticeably improved.