pnmsmooth - smooth out an image
pnmsmooth [pnmfile]
Smooths out an image by replacing each pixel with the average of its
nine immediate neighbors. It is implemented as a simple script using
pnmconvol.
pnmconvol(1), pnm(5)
It's a script. Scripts are not portable to non-Unix environments.
Copyright (C) 1989, 1991 by Jef Poskanzer.