Use of a class of two-dimensional functions for blocking artifacts reduction in image coding

We propose a novel blocking artifacts reduction method in image coding based on the least square block discontinuity criterion. We define the “inner product on the block boundaries” for N×N 2-D functions to introduce the concept of the “boundary-orthogonal 2-D functions”. The proposed post-processing approach attempts to find the coefficients of the boundary-orthogonal 2-D functions whose pel-by-pel sum is added to the blocky image to minimize the block discontinuity. Experimental results, using DCT-based compressed images, are provided to show the performance of the proposed scheme. In the experiments, as a special case of the proposed method, we use three terms of 2-D DCT functions which turn out to be simple but very effective in reducing blocking artifacts