Post-processing of block-coded images at low bit rates

A post-processing method suitable for low bit rate spatial domain block-coded images is described. An adaptive filtering process is employed to reduce the visually annoying artefacts introduced from compression. The decision-based filtering uses an estimation of the local characteristics of the coded image. For the areas of low image detail a smoothing operator is used; whereas in the high image detail areas (edges, texture) an adaptive Gaussian-type filter is employed. The main advantage of this filter is that the shape and the position of the Gaussian kernel are adjusted according to the characteristics of the local image region. Simulation results demonstrate that this method enhances the quality of coded edges and reduces annoying blocking effects, resulting in a better picture quality.