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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<TITLE>The PNM Format</TITLE>
<META NAME="manual_section" CONTENT="5">
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<BODY>
<H1>pnm</H1>
Updated: 27 November 2013
<BR>
<A HREF="#index">Table Of Contents</A>
<H2>NAME</H2>
pnm - Netpbm superformat
<H2 id="description">DESCRIPTION</H2>
<P>The PNM format is just an abstraction of the PBM, PGM, and PPM
formats. I.e. the name "PNM" refers collectively to
PBM, PGM, and PPM.
<P>The name "PNM" is an acronym derived from "Portable
Any Map." This derivation makes more sense if you consider
it in the context of the other Netpbm format names: PBM, PGM, and PPM.
<P>The more general term "Netpbm format" refers to the PNM
formats plus PAM.
<p>PNM is principally used with <a href="index.html">Netpbm</a>.
<P>Note that besides being names of formats, PBM, PGM, PPM, and PNM
are also classes of programs. A PNM program can take PBM, PGM, or PPM
input. That's nothing special -- a PPM program can too. But a PNM
program can often produce multiple output formats as well, and a PNM
program can see the difference between PBM, PGM, and PPM input and
respond to each differently whereas a PPM program sees everything as
if it were PPM. This is discussed more in <a href="index.html">the
description of the netpbm programs</a>.
<P>"pnm" also appears in the names of the most general <a
href="libnetpbm.html">Netpbm library routines</a>, some of which aren't even
related to the PNM format.
<h2 id="internetmediatype">INTERNET MEDIA TYPE</h2>
<p>No Internet Media Type (aka MIME type, content type) for PNM has been
registered with the IANA, but the value <tt>image/x-portable-anymap</tt>
is conventional.
<p>Note that there are also conventional Internet Media Types for each of the
PNM subformats. The recommended practice is to use those in preference to the
PNM code when it is convenient to do so.
<h2 id="filename">FILE NAME</h2>
<p>There are no requirements on the name of a PNM file, but the convention is
to use the suffix "pbm", "pgm", or "ppm",
depending on the particular subformat, or "pnm" if it is not
convenient to distinguish the subformats.
<H2 id="seealso">SEE ALSO</H2>
<A HREF="ppm.html">ppm</A>,
<A HREF="pgm.html">pgm</A>,
<A HREF="pbm.html">pbm</A>,
<A HREF="pam.html">pam</A>,
<A HREF="directory.html">programs that process PNM</A>,
<A HREF="libnetpbm.html">libnetpbm</A>
<HR>
<H2 id="index">Table Of Contents</H2>
<UL>
<LI><A HREF="#description">DESCRIPTION</A>
<li><A HREF="#internetmediatype">INTERNET MEDIA TYPE</A>
<li><A HREF="#filename">FILE NAME</A>
<LI><A HREF="#seealso">SEE ALSO</A>
</UL>
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