pnmarith - perform arithmetic on two portable anymaps
SYNOPSIS
pnmarith -add|-subtract|-multiply|-difference|-mini
mum|-maximum. pnmfile1 pnmfile2
DESCRIPTION
Reads two portable anymaps as input. Performs the speci
fied 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 pre
fix.
SEE ALSO
pbmmask(1), pnmpaste(1), pnminvert(1), pnm(5)
AUTHOR
Copyright (C) 1989, 1991 by Jef Poskanzer. Lightly modi
fied by Marcel Wijkstra <wijkstra@fwi.uva.nl>
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