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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2010-02-03 15:19:51 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2010-02-03 15:19:51 +0000 |
| commit | 8bb2dba8170bf75940143c1cf2933230e9329551 (patch) | |
| tree | a7d678fe1a1634e045fb588cc99ac1ab4648eab8 /pnmhisteq.html | |
| parent | 910b6948e1f40d4942f7f4e7ee4149d6cfe52a94 (diff) | |
| download | netpbm-mirror-8bb2dba8170bf75940143c1cf2933230e9329551.tar.gz netpbm-mirror-8bb2dba8170bf75940143c1cf2933230e9329551.tar.xz netpbm-mirror-8bb2dba8170bf75940143c1cf2933230e9329551.zip | |
"miscellaneous update"
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@1118 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'pnmhisteq.html')
| -rw-r--r-- | pnmhisteq.html | 56 |
1 files changed, 25 insertions, 31 deletions
diff --git a/pnmhisteq.html b/pnmhisteq.html index 9416beb9..f5323a8e 100644 --- a/pnmhisteq.html +++ b/pnmhisteq.html @@ -2,17 +2,15 @@ <HTML><HEAD><TITLE>Pnmhisteq User Manual</TITLE></HEAD> <BODY> <H1>pnmhisteq</H1> -Updated: 10 September 2005 +Updated: 02 February 2010 <BR> <A HREF="#index">Table Of Contents</A> -<A NAME="lbAB"> </A> <H2>NAME</H2> pnmhisteq - histogram equalize a PNM image -<A NAME="lbAC"> </A> -<H2>SYNOPSIS</H2> +<H2 id="synopsis">SYNOPSIS</H2> <B>pnmhisteq</B> @@ -27,8 +25,7 @@ pnmhisteq - histogram equalize a PNM image [<I>pnmfile</I>] -<A NAME="lbAD"> </A> -<H2>DESCRIPTION</H2> +<H2 id="description">DESCRIPTION</H2> <p>This program is part of <a href="index.html">Netpbm</a>. @@ -69,6 +66,13 @@ bucket <i>j</i> with one whose luminosity is: pixels in the most luminous bucket become white. Pixels in the 10th per centile of luminosity become 10% of white. +<p><b>pnmhisteq</b> maps a single luminosity in the input to a single +luminosity in the output. That means if pixels A and B both have luminosity +.2 in the input, and pixel A has luminosity .4 in the output, pixel B also has +luminosity .4 in the output. And since the luminosities in the input are not +continuous, the luminosities in the output aren't either and <b>pnmhisteq</b> +doesn't meet the ideal of having exactly the same number of pixels of each +luminosity in the output. <P>If you're processing a related set of images, for example frames of an animation, it's generally best to apply the same luminosity mapping @@ -84,9 +88,15 @@ Then, you can run <b>pnmisteq</b> with <b>-rmap</b> on each of the individual images, using the luminosity map you generated from the composite. +<p>Use <b>pnmhistmap</b> to see the result. Run a color image through +<b>ppmtopgm</b> first so that you see a histogram of the luminosity instead of +histograms of the three color components. It should generally show a flat +histogram. But due to the quantization effects described above, you might see +high bars interleaved with low bars, with the local average being flat. To +see local averages, use the <b>-width</b> option of <b>pnmhistmap</b>. -<A NAME="lbAE"> </A> -<H2>OPTIONS</H2> + +<H2 id="options">OPTIONS</H2> <P>You can abbreviate any option to its shortest unique prefix. @@ -127,8 +137,7 @@ map. </DL> -<A NAME="lbAF"> </A> -<H2>LIMITATIONS</H2> +<H2 id="limitations">LIMITATIONS</H2> <p>Histogram equalization is effective for increasing the visible detail in scientific imagery and in some continuous-tone pictures. It @@ -148,8 +157,7 @@ image. identity operation), the only effect of passing the file through <B>pnmhisteq</B> will be the passage of time. -<A NAME="lbAG"> </A> -<H2>SEE ALSO</H2> +<H2 id="seealso">SEE ALSO</H2> <B><A HREF="pnmnorm.html">pnmnorm</A></B>, @@ -169,29 +177,15 @@ Press, 1992. Pages 105-110. </DL> -<A NAME="lbAH"> </A> -<H2>AUTHOR</H2> - -<p>Copyright (C) 1995 by John Walker (<A -HREF="mailto:kelvin@fourmilab.ch">kelvin@fourmilab.ch</A>). WWW home -page: <A HREF="http://www.fourmilab.ch/">http://www.fourmilab.ch/</A> - -<P>Permission to use, copy, modify, and distribute this software and -its documentation for any purpose and without fee is hereby granted, -without any conditions or restrictions. This software is provided -"as is" without express or implied warranty. - <HR> <A NAME="index"> </A> <H2>Table Of Contents</H2> <UL> -<LI><A HREF="#lbAB">NAME</A> -<LI><A HREF="#lbAC">SYNOPSIS</A> -<LI><A HREF="#lbAD">DESCRIPTION</A> -<LI><A HREF="#lbAE">OPTIONS</A> -<LI><A HREF="#lbAF">BUGS</A> -<LI><A HREF="#lbAG">SEE ALSO</A> -<LI><A HREF="#lbAH">AUTHOR</A> +<LI><A HREF="#synopsis">SYNOPSIS</A> +<LI><A HREF="#description">DESCRIPTION</A> +<LI><A HREF="#options">OPTIONS</A> +<LI><A HREF="#limitations">LIMITATIONS</A> +<LI><A HREF="#seealso">SEE ALSO</A> </UL> </BODY> </HTML> |