This program is part of Netpbm.
pnmmargin adds a border around a PNM image.
pnmfile is the name of the input file. If you don't specify this argument, pnmmargin reads the input image from its Standard Input.
In addition to the options common to all programs based on libnetpbm (most notably -plain, see Common Options), pnmmargin recognizes the following command line options:
You can specify the border color with the -white, -black, and -color options. If you don't specify a color, the program makes a guess.
The value of -color is like the argument of the pnm_parsecolor() library routine.
The -plain common option was implemented beginning with Netpbm version 10.40 (September 2007).
The -quiet common option is not implemented.
pnmpad does essentially the same thing, but gives you more control over the individual margins and does only black and white margins.
To remove a border of a specified size from an image, usepamcut. pnmcrop also removes borders, but determines by itself what is border and what is subject.
If you want to make the image a certain required size, adding borders or cropping as necessary, pamcut may be what you want.