about MHRF means Maximum Homogeneous Region Filter (by Yifeng Wu & Henri Maitre)
algorithm This function is an adaptive median filter that can recognize edges, near-edges, pikes and homogeneous regions. It is based on the moving window algorithm and the window size is growing from 3x3 until an edge is detected (variance given by threshold T3 is exceeded). If no edge is detected window size is stopped from growing when it's size is wmax*2+1.
The algorithm performs as a median filter with a very large window size when the pixel does not belong to an edge and it leaves the pixel unchanged otherwise.