pnmmargin - add a border to a portable anymap
pnmmargin [-white|-black|-color colorspec] size [pnmfile]
Reads a portable anymap as input. Adds a border of the specified number of pixels, and produces a portable anymap as output.
You can specify the border color with the -white, -black, and -color flags. If no color is specified, the program makes a guess.
It’s a script. Scripts are not portable to non-Unix environments.
Copyright (C) 1991 by Jef Poskanzer.