Edge-preserving filter

Noise reduction of a grayscale image preserving the sharp edges of objects. Is based initially on the work of Kuwahara, then Schulze and Pearce. In contrast to the latter, which retain for a given point, the local mean of the lowest variance, a linear combination of the local means in the vicinity is held according to the local variances, by weighting more strongly acording low variances.

References :
M. Kuwahara et al. Processing of RI-angiocardiographic images. In: Preston Jr, K., Onoe, M. (eds.) Digital Processing of Biomedical Images,Plenum, New York, pp. 187–202 (1976).
M.A. Schulze and J.A. Pearce, "A morphology-based filter structure for edge-enhancing smoothing ," Proceedings. ICIP 1994., IEEE, vol. 2, 13–16, pp. 530–34 (1994).