NAME
    pnmarith - perform arithmetic on two portable anymaps

SYNOPSIS
    pnmarith  -add|-subtract|-multiply|-difference|-minimum|-maximum. pnm-
    file1 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>