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<H1>pgmdeshadow</H1>
Updated: 06 July 2006
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<A HREF="#index">Table Of Contents</A>
<H2>NAME</H2>
pgmdeshadow - Deshadow a PGM image
<H2 id="synopsis">SYNOPSIS</H2>
<B>pgmdeshadow</B>
[<I>pnmfile</I>]
<H2 id="description">DESCRIPTION</H2>
<p>This program is part of <a href="index.html">Netpbm</a>.
<p><b>pgmdeshadow</b> removes gray shadows from an image. This is
useful for an image containing text, such as a scanned book pages,
where a shadow typically appears near the book crease or near one side
of the image. <b>pgmdeshadow</b> recognizes a gray shadow as an area
of smoothly changing color, starting from the outer edges of the
image. The program uses a simple image reconstruction algorithm to
determine the local shadow gray level, then divides each pixel's gray
level by the local shadow gray level.
<p>The algorithm is the "fast hybrid grayscale reruction"
algorithm from Luc Vincent, "Morphological Grayscale Reruction in
Image Analysis: Applications and Efficient Algorithms.
<H2 id="options">OPTIONS</H2>
<p>None.
<H2 id="references">REFERENCES</H2>
<ul>
<li>Luc Vincent, "Morphological Grayscale Reconstruction in Image
Analysis: Applications and Efficient Algorithms," IEEE
Transactions on Image Processing, vol. 2, no. 2, April 1993,
pp. 176-201.
</ul>
<H2 id="seealso">SEE ALSO</H2>
<A HREF="ppmshadow.html">ppmshadow</A>,
<A HREF="pgm.html">pgm</A>
<h2 id="history">HISTORY</h2>
<P><b>pgmdeshadow</b> was added to Netpbm in Version 10.35 (August 2006).
<HR>
<H2 id="index">Table Of Contents</H2>
<UL>
<LI><A HREF="#synopsis">SYNOPSIS</A>
<LI><A HREF="#description">DESCRIPTION</A>
<LI><A HREF="#options">OPTIONS</A>
<LI><A HREF="#references">REFERENCES</A>
<LI><A HREF="#seealso">SEE ALSO</A>
<LI><A HREF="#history">HISTORY</A>
</UL>
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