pnmpad

Add borders to a PNM image. See also: pnmmargin, pamcut, pamcomp. More information: https://netpbm.sourceforge.net/doc/pnmpad.html.

pnmpad -left 100 -right 150 -top 123 -bottom 456 path/to/image.pnm > path/to/output.pnm

pnmpad -width 1000 -height 500 path/to/image.pnm > path/to/output.pnm

pnmpad -width 1000 -halign 0.7 path/to/image.pnm > path/to/output.pnm

pnmpad -width 1000 -color red path/to/image.pnm > path/to/output.pnm