Rank order filters
A rank order filter of size 3x3 for example, examines 9 pixel values of the input map at a time, sorts these values from small to large, and selects as output value that value which is encountered at a certain rank order number.
Standard rank order filters are the median filters: MED3x3 and MED5x5. The median filters can for instance be used to smooth an image.
Furthermore, user-defined rank order and median filters can be used; specify the size of a rank order filter, the rank order number and a threshold. In this way you can obtain for example the minimum or maximum value of a number of pixels examined.