On the gradient inverse weighted filter (image processing)

D.C.C. Wang et al. (1981) presented a gradient inverse weighted (GIW) filter. The proposed noise smoothing scheme is based on the observation that variations of gray levels inside a region are smaller than those between regions. Reducing noise without smearing edges is the advantage of this nonlinear filter. As an improvement of the GIW filter, a new algorithm is introduced. Examples show that it can preserve edges and smooth noise more efficiently.>