Some properties of the two-dimensional pseudomedian filter
Mark A. Schulze, John A. Pearce · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1991
The pseudomedian filter was designed to be a computationally efficient alternative to the median filter. The output of the pseudomedian filter is the average of two values obtained by maximum and minimum operations performed on selected subwindows within the filter window. Although the response of the pseudomedian filter resembles that of the median filter in many ways, there are important differences. The pseudomedian filter is more susceptible to impulse-like noise in images, but the square-shaped 2D pseudomedian filter does not round off sharp corners as much as the square-shaped 2D median filter does. The psuedomedian filter also removes high- frequency periodic elements from images. The pseudomedian filter exhibits a more 'center-weighted' response than the median filter. Thus, fine details that are completely removed by the median filter usually remain visible in pseudomedian- filtered images. Images filtered by a square-shaped 2D pseudomedian filter often have a 'blocky' appearance caused by the square shape of the filter subwindows. These properties of the pseudomedian filter indicate that it may be more appropriate than the median filter for processing images with sharp corners or fine details.