freebsd man page for pnmarith

pnmarith(1)                                                   General Commands Manual                                                  pnmarith(1)

NAME
       pnmarith - perform arithmetic on two portable anymaps

SYNOPSIS
       pnmarith -add|-subtract|-multiply|-difference|-minimum|-maximum.  pnmfile1 pnmfile2

DESCRIPTION
       Reads two portable anymaps as input.  Performs the specified arithmetic operation, and produces a portable anymap as output.  The two input
       anymaps must be the same width and height.

       The arithmetic is performed between corresponding pixels in the two anymaps, as if maxval was 1.0, black was 0.0, and  a  linear  scale  in
       between.  Results that fall outside of [0..1) are truncated.

       The operator -difference calculates the absolute value of pnmarith -subtract pnmfile1 pnmfile2, i.e. no truncation is done.

       All flags can be abbreviated to their shortest unique prefix.

SEE ALSO
       pbmmask(1), pnmpaste(1), pnminvert(1), pnm(5)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.  Lightly modified by Marcel Wijkstra <wijkstra@fwi.uva.nl>

                                                                  26 August 1993                                                       pnmarith(1)