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diff --git a/pgmkernel.html b/pgmkernel.html index 20face18..a0bdaaae 100644 --- a/pgmkernel.html +++ b/pgmkernel.html @@ -2,22 +2,23 @@ <HTML><HEAD><TITLE>Pgmkernel User Manual</TITLE></HEAD> <BODY> <H1>pgmkernel</H1> -Updated: 10 December 1992 +Updated: 19 December 2013 <BR> <A HREF="#index">Table Contents</A> -<A NAME="lbAB"> </A> <H2>NAME</H2> pgmkernel - generate a convolution kernel -<A NAME="lbAC"> </A> -<H2>SYNOPSIS</H2> +<H2 id="synopsis">SYNOPSIS</H2> -<B>pgmkernel</B> [<B>-weight</B> <I>w</I>] <I>width </I> [<I>height </I>] +<p> +<B>pgmkernel</B> [<B>-weight</B> <I>number</I>] <I>size</I> -<A NAME="lbAD"> </A> -<H2>DESCRIPTION</H2> +<p> +<B>pgmkernel</B> [<B>-weight</B> <I>number</I>] <I>width</I> <I>height</I> + +<H2 id="description">DESCRIPTION</H2> <p>This program is part of <a href="index.html">Netpbm</a>. @@ -25,9 +26,9 @@ pgmkernel - generate a convolution kernel with <b>pnmconvol</b>. The kernel is one where the weight of each location is inversely proportional to its distance from the center of the kernel. -<p><b>pgmkernel</b> generates a PGM image of size <I>width</I> by -<I>height</I> (or <I>width</I> by <I>width</I> if you don't specify -<I>height</I>. +<p><b>pgmkernel</b> generates a PGM image of width and height <I>size</I> +if you specify one argument, or width <i>width</i> and height <i>height</i> +if you specify two arguments. <p><b>pgmkernel</b> computes the convolution function K as follows. @@ -39,24 +40,34 @@ where <I>w</I> is a coefficient specified via the <b>-weight</b> option. <i>i</i> and <i>j</i> are measured in pixels. K is zero everywhere beyond the specified kernel width and height. -<P><b>pgmkernel</b> generates the output PGM file in the Plain (text) -variation of PGM. +<p>The sample values in the PGM output have this value scaled and biased using +the protocol <b>pnmconvol</b> specifies for representing the real numbers K +in PGM. -<A NAME="lbAE"> </A> -<H2>OPTIONS</H2> +<H2 id="options">OPTIONS</H2> -The optional <b>-weight</b> value should be a real number greater than --1. The default value is 6.0. +The optional <b>-weight</b> value must be a positive real number. The default +value is 6.0. -<A NAME="lbAF"> </A> -<H2>LIMITATIONS</H2> +<h2 id="limitations">LIMITATIONS</H2> <P>The computation time is proportional to <I>width</I>*<I>height</I>. This increases rapidly with the increase of the kernel size. A better approach could be using a FFT in these cases. -<A NAME="lbAG"> </A> -<H2>SEE ALSO</H2> +<h2 id="history">HISTORY</h2> + +<p>Before Netpbm 10.65 (December 2013), the output was always in +Plain (text) PGM format. (Now, like standard Netpbm programs, the default +is raw PGM and you can get Plain PGM with a <b>-plain</b> option). + +<p>Before Netpbm 10.65 (December 2013), this manual said negative values +for <b>-weight</b> were valid (as long as they were greater than -1.0). But +the program never worked with negative numbers and it isn't clear that the +result would be useful, so <b>-weight</b> is now required to be nonnegative +and the program fails gracefully if you specify a negative value. + +<H2 id="seealso">SEE ALSO</H2> <A HREF="pnmconvol.html">pnmconvol</A>, <A HREF="pnmsmooth.html">pnmsmooth</A> @@ -64,24 +75,22 @@ approach could be using a FFT in these cases. <A HREF="pgm.html">pgm</A> -<A NAME="lbAH"> </A> -<H2>AUTHOR</H2> +<H2 id="author">AUTHOR</H2> Alberto Accomazzi (<A HREF="mailto:alberto@cfa.harvard.edu">alberto@cfa.harvard.edu</A>). <HR> -<A NAME="index"> </A> -<H2>Table Of Contents</H2> +<H2 id="index">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="#history">HISTORY</A> +<LI><A HREF="#seealso">SEE ALSO</A> +<LI><A HREF="#author">AUTHOR</A> </UL> </BODY> </HTML> |