Salt and pepper noise filtering algorithm based on two stage noise detection

As the present algorithms are not suitable to be applied to denoise images containing different density salt and pepper noise,a switching filter based on noise′s extreme value and directional difference is proposed.In noise detection stage,it adopts the Minimum-maximum noise detector and calculates the noise density.Then it detects the noise for the second time based on the noise′s directional difference if the density is lower than the threshold,otherwise direct filtering is made.In filtering stage,the proposed algorithm selects a recursive or non-recursive window according to the partial noise density and realizes the weighted mean filtering for removing the noise.Experimental results indicate that the filtering performance and edge-preserving of the proposed algorithm are superior to the traditional median filer and some improved algorithm.