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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN">
<HTML><HEAD>
<TITLE>Ppmtogif User Manual</TITLE></HEAD>
<BODY>
<H1>ppmtogif</H1>
<BR>
<p><b>ppmtogif</b> was replaced in Netpbm 10.37 (December 2006) by
<b><a href="pamtogif.html">pamtogif</a></b>.
<P><B>pamtogif</b> is mostly backward compatible with <b>ppmtogif</b>.
<P>One way <b>pamtogif</b> is not backward compatible with <b>ppmtogif</b>
is that to specify a transparency (alpha) mask with <b>ppmtogif</b>, you
supply the transparency as a separate pseudo-PGM image and use the
<b>-alpha</b> option, whereas with <b>pamtogif</b>, you supply an input
image that has the transparency integrated into it, and there is no
<b>-alpha</b> option.
<p><b>ppmtogif</b> still exists as a separate program for backward
compatibility, but it runs <b>pamtogif</b> to do the essential work.
The compatibility <b>ppmtogif</b> interprets an <b>-alpha</b> option
by reading the transparency image and combining it with the input
image, then feeding <b>pamtogif</b> the combined image it expects.
Other than that, the compatibility <b>ppmtogif</b> just passes input and
options directly to <b>pamtogif</b>.
<P>You should not make any new use of <b>ppmtogif</b> and if you modify an
existing use, you should upgrade to <b>pamtogif</b>. But note that if you
write a program that might have to be used with old Netpbm, <b>ppmtogif</b> is
the only way to do that.
<p>Unless you use the <b>-alpha</b> option, you can simply change the name
of the program. If you use <b>-alpha</b>, here is how to upgrade:
<pre>
<kbd>
$ ppmtogif -alpha=myalpha.pgm myinput.ppm >myoutput.gif
</kbd>
</pre>
becomes
<pre>
<kbd>
$ pamstack -tupletype=RGB_ALPHA myinput.ppm myalpha.pgm | \
pamtogif >myoutput.gif
</kbd>
</pre>
<h2>Original Ppmtogif</h2>
<p>If you are using Netpbm before 10.37, <b>pamtogif</b> doesn't exist,
so you use <b>ppmtogif</b>. You can use the <b>pamtogif</b> manual
for <b>ppmtogif</b>, with the following exceptions.
<p>The current documentation of <b>pamtogif</b> documents all versions
of that program. Use the information for Version 10.37 only.
<p><b>ppmtogif</b> before Netpbm 10.31 does not accept PAM input at all.
<p><b>ppmtogif</b> does not accept PAM input with transparency information
in it. Instead, <b>ppmtogif</b> has an <b>-alpha</b> option.
<p>The syntax of the option is <b>-alpha=</b><i>pgmfile</i>.
<b>ppmtogif</b> treats the contents of the named PGM file the same as
<b>pamtogif</b> 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.
<b>ppmtogif</b> interprets the alpha file using the alpha file's
maxval.
<P>You cannot specify both <B>-transparent</B> and <B>-alpha</B>.
</BODY>
</HTML>
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