POCS-based blocking artifacts suppression with region smoothness constraints for graphic images

It is well known that low bit rate BDCT coded image exhibits visually annoying coding artifacts. In this paper, we proposed a POCS-based deblocking algorithm using a novel region smoothness constraint for the class of graphic images. For this type of images, there usually exist large smooth varying regions in the images. Current POCS based deblocking algorithms usually do not enforce smoothness across several blocks. In our method, the BDCT coded image is modeled using a smooth, spatially adaptive, thin-plate spline surface, and region smoothness constraint set is constructed from this spline surface. The spline modeling allows us to model the long range smoothness across smooth region. Simulation experiments indicated that blockiness in smooth regions is effectively suppressed while genuine edges are preserved.