Optimal JPEG decoding

This paper introduces an optimal decoding scheme for the baseline Joint Photographers Expert Group (JPEG) standard. In particular, it deals with the minimization of a half-quadratic criterion which takes into account observed data, a priori knowledge of the solution, and precise spatial location of blocking artifacts. The method considers, at the same time, information in the original spatial domain, in the DCT domain, and in the spatio-frequency (DWT) domain. A model of the quantizer is also included. The method reduces blocking and ringing artifacts, resulting in improved peak signal-to-noise ratio performance as well as greater visual quality.