A simple and effective filter based on the rank difference

We have developed a simple and effective filter for edge detection, called the rank difference filter. This filter is simple, employing only integer operations to implement and generates results comparable to or better than more complex edge detectors such as the Laplacian of Gaussian and the Canny (1986). For each pixel, we first apply two different rank filters. We then take the difference of the two rank filter results and assign it to that pixel. The parameters that determine the behavior of the rank difference filter are: (i) the alignment pixel location in the filter kernel, (ii) the kernel´s shape, (iii) the kernel´s size, and (iv) the values of the upper and lower rank numbers. This filter has properties that out-perform those of other filters especially when applied to images corrupted by uniform noise. In addition, the rank difference filter can also be used as a selective morphologic filter