Ppmtogif User Manual(0) Ppmtogif User Manual(0)NAMEppmtogif was replaced in Netpbm 10.37 (December 2002) by pamtogif(1)SYNOPSIS
pamtogif is mostly backward compatible with ppmtogif.
DESCRIPTION
One way pamtogif is not backward compatible with ppmtogif is that to
specify a transparency (alpha) mask with ppmtogif, you supply the
transparency as a separate pseudo-PGM image and use the -alpha option,
whereas with pamtogif, you supply an input image that has the trans‐
parency integrated into it, and there is no -alpha option.
ppmtogif still exists as a separate program for backward compatibility,
but it runs pamtogif to do the essential work. The compatibility ppm‐
togif interprets an -alpha option by reading the transparency image and
combining it with the input image, then feeding pamtogif the combined
image it expects. Other than that, the compatibility ppmtogif just
passes input and options directly to pamtogif.
You should not make any new use of ppmtogif and if you modify an exist‐
ing use, you should upgrade to pamtogif.
Unless you use the -alpha option, you can simply change the name of the
program. If you use -alpha, here is how to upgrade:
$ ppmtogif -alpha=myalpha.pgm myinput.ppm >myoutput.gif
becomes
$ pamstack -tupletype=RGB_ALPHA myinput.ppm myalpha.pgm | \
pamtogif >myoutput.gif
Original Ppmtogif
If you are using Netpbm before 10.37, pamtogif doesn't exist, so you
use ppmtogif. You can use the pamtogif manual for ppmtogif, with the
following exceptions.
The current documentation of pamtogif documents all versions of that
program. Use the information for Version 10.37 only.
ppmtogif before Netpbm 10.31 does not accept PAM input at all.
ppmtogif does not accept PAM input with transparency information in it.
Instead, ppmtogif has an -alpha option.
The syntax of the option is -alpha=pgmfile. ppmtogif treats the con‐
tents of the named PGM file the same as pamtogif treats the alpha plane
of a PAM. The PGM image must have the same dimensions as the input
file. But unlike the PAM case, the alpha image need not have the same
maxval as the input. ppmtogif interprets the alpha file using the
alpha file's maxval.
You cannot specify both -transparent and -alpha.
netpbm documentation Ppmtogif User Manual(0)
