Image deringing using quadtree based block-shift filtering

In this paper, we propose an efficient spatial domain deringing algorithm using quadtree (QT) decomposition and block-shift filtering (BSF). The ringing artifacts are located through the QT decomposition of an image down to the 4times4 block size. The blocks with suspicious ringing are then replaced with the weighted average of itself and pixel-by-pixel shifted neighboring blocks. The block shifting range is up to 9times9 and only those shifted blocks resembling the center one are involved in the averaging stage. Experimental results show that the proposed deringing algorithm can effectively suppress the ringing artifact while preserving image edges and textures well, and the method substantially outperforms most of the existing deringing algorithms reported in the literature, both subjectively and objectively.