Reducing Blocking Artifacts in Compressed Images via Transform-Domain Non-local Coefficients Estimation

Block transform coding using discrete cosine transform is the most popular approach for image compression. However, many annoying blocking artifacts are generated due to coarse quantization on transform coefficients independently. This paper proposes an effective blocking artifacts reduction method by estimating the transform coefficients from their quantized version. In the proposed scheme, we estimate the transform coefficients based on an image statistic model and non-local similarity among blocks in transform domain. The parameters used in our proposed scheme are discussed and adaptively selected. Extensive experimental results show that our proposed method significantly reduces blocking artifacts and improves the subjective and the objective quality of block transform coded images.