pgmmorphconv performs morphological convolutions on a PGM image: dilation and erosion.
These are topological measures of the image, which means that they are very robust under all sorts of deformations. On top of that they are very easy to calculate quickly. This makes them of interest for some kinds of pattern recognition. For more info, see e.g. K. Michielsen and H. De Raedt, "Integral-Geometry Morphological Image Analysis", Phys. Rep. 347, 461-538 (2001).
Based on work which is Copyright (C) 1989, 1991 by Jef Poskanzer.