pgmnoise - create a graymap made up of white noise
pgmnoise width height
Creates a portable graymap that is made up of random pixels
with gray values in the range of 0 to PGM_MAXMAXVAL (depends
on the compilation, either 255 or 65535). The graymap has a
size of width * height pixels.
Copyright (C) 1993 by Frank Neumann