Embedded post-processing for enhancement of compressed images

This paper presents a simple and effective post-processing method for compressed images. This work focuses on the cyclic time-variance introduced by block-based and subband transform coders. We propose an algorithm to (almost) restore stationarity to the cyclo-stationary output of the conventional transform coders. Despite a simple, non-iterative structure, this method outperforms other methods of image enhancement known to us, e.g. linear and nonlinear filtering, projection on convex sets (POCS), wavelet-based and optimization-based methods. In particular, the proposed method performs very well in suppressing both blocking and ringing artifacts. Furthermore, it admits a solution with successive approximation. The resulting embeddedness is very useful for multimedia applications such as image browsing on the World Wide Web.