Frequency response of 2-D median filters

Because of their unique nonlinear features medians are used in filtering procedures since many years, both in one- or twodimensional procedures, medians are able to reject numbers or signal samples differing substantially from all neighbouring elements of a sequence. On the other hand medians can be approximately described by their frequency characteristics, which are typically used for linear circuits. An analysis of frequency responses for some popular median windows in twodimensional case is given in the contribution.