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<H1>pamdepth</H1>
Updated: 19 December 2013
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<A HREF="#index">Table Of Contents</A>
<H2>NAME</H2>
pamdepth - change the depth (color resolution) in a Netpbm image
<H2 id="synopsis">SYNOPSIS</H2>
<B>pamdepth</B> <I>newmaxval</I> [<I>netpbmfile</I>]
<H2 id="description">DESCRIPTION</H2>
<p>This program is part of <a href="index.html">Netpbm</a>.
<p><b>pamdepth</b> reads a Netpbm image as input, changes its depth (color
resolution), and writes out the resulting Netpbm image. I.e. the output has a
different maxval from the input, but all the same colors (apart from rounding
error).
<p>Reducing the depth results in some loss of information.
<p>Here is an example of the effect at the image format level: Assume you
start with an image with maxval 100 and sample values of 50 and 100. You
tell <b>pamdepth</b> to change it to depth 150. The output has maxval
200 and sample values 75 and 150.
<p>This program works on multi-image streams.
<P>Be careful of off-by-one errors when choosing the new maxval. For
instance, if you want the color values to be five bits wide, use a
maxval of 31, not 32.
<P>One important use of <B>pamdepth</B> is to convert a new format
2-byte-per-sample PNM file to the older 1-byte-per-sample format.
Before April 2000, essentially all raw (binary) format PNM files had a
maxval less than 256 and one byte per sample, and many programs may
rely on that. If you specify a <I>newmaxval</I> less than 256, the
resulting file should be readable by any program that worked with PNM
files before April 2000.
<H2 id="seealso">SEE ALSO</H2>
<A HREF="pnm.html">pnm</A>,
<A HREF="pam.html">pam</A>,
<A HREF="pnmquant.html">pnmquant</A>,
<A HREF="ppmdither.html">ppmdither</A>
<A HREF="ppmbrighten.html">ppmbrighten</A>
<A HREF="pamfunc.html">pamfunc</A>
<h2 id="history">HISTORY</h2>
<p><b>pamdepth</b> was new in Netpbm 10.32 (February 2006). It replaced
<b>pnmdepth</b>, by Jef Poskanzer. <b>pamdepth</b> is backward compatible
with <b>pnmdepth</b> and adds the ability to process arbitrary PAM images
and the ability to process multi-image input streams. <b>pnmdepth</b>
handled only PNM images and ignored all but the first in any stream.
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<H2 id="index">Table Of Contents</H2>
<UL>
<LI><A HREF="#synopsis">SYNOPSIS</A>
<LI><A HREF="#description">DESCRIPTION</A>
<LI><A HREF="#seealso">SEE ALSO</A>
<LI><A HREF="#history">HISTORY</A>
</UL>
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