Projection onto adaptive quantization constraint set for postprocessing of block-coded image

For the present, block-transform coding is probably the most popular approach for image compression. However, for the sake of its implementation, an image is partitioned into blocks and they are processed independently without considering inter-block correlation. So this approach inescapably causes annoying artifacts called blocking artifacts. A new quantization constraint set based on the theory of projection onto convex sets (POCS) is proposed in order to reduce blocking artifacts appearing in block-coded images. Experimental results show that the projection onto the proposed quantization constraint set not only obtains better performance but also maintains the clearness of the decoded image, as compared with that onto the conventional quantization constraint set