Thresholded Weighted Median Filters for Ringing Reduction in Processed Images

In this paper, we present how thresholded weighted median filters (WMFs), can significantly improve visual as well as objective quality of images affected by ringing. Ringing is identified by its structural properties and WMFs are chosen according to these structures. Since WMFs are concerned with the relative values of their input but do not consider its absolute values, we explicitly enforce a limited filter output. In this paper we analyze the formation of ringing and match thresholded WMFs for example applications. For image resampling, we are able to obtain a significantly decreased amount of ringing. As a post-filter of a lossy wavelet-coder, typical PSNR gains around 0.4 dB are obtained while visually, ringing is reduced to a very pleasing extent