A DCT based Algorithm for Blocking Artifact Reduction from DCT Coded Images

The edge component causes the high frequency components in the transformed domain. Thus, examining the discrete cosine transform (DCT) coefficients of the block itself can identify the monotone blocks. Moreover, the artificial discontinuities in monotone area due to blocking artifacts also cause the high frequency components in DCT domain. Thus, these discontinuities are reflected as high frequency components in the DCT of concatenated block of two or more neighboring monotone blocks. It is also found that there exists a relationship between the DCT coefficient of two monotone blocks and that of concatenated block. The DCT coefficients due to blocking artifacts are present in the concatenated block but not in individual block. Therefore, from the relationship between the DCT coefficients of monotone block of different sizes we can detect the high frequency components due to blocking artifacts and thus we can eliminate them to reduce the blocking artifacts.