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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2010-01-03 20:08:33 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2010-01-03 20:08:33 +0000 |
| commit | f587b59e9998665880a14e3691114d7a4fb309ad (patch) | |
| tree | bd4690db8c1ef60a78c9f085b44be17e8a97b218 | |
| parent | 62c34c8bfece6ad6c7091897dcd4f20285bbd79b (diff) | |
| download | netpbm-mirror-f587b59e9998665880a14e3691114d7a4fb309ad.tar.gz netpbm-mirror-f587b59e9998665880a14e3691114d7a4fb309ad.tar.xz netpbm-mirror-f587b59e9998665880a14e3691114d7a4fb309ad.zip | |
"miscellaneous update"
git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@1091 9d0c8265-081b-0410-96cb-a4ca84ce46f8
| -rw-r--r-- | pnmconvol.html | 47 |
1 files changed, 43 insertions, 4 deletions
diff --git a/pnmconvol.html b/pnmconvol.html index b61ff40c..c9c0e5b3 100644 --- a/pnmconvol.html +++ b/pnmconvol.html @@ -2,7 +2,7 @@ <HTML><HEAD><TITLE>Pnmconvol User Manual</TITLE></HEAD> <BODY> <H1>pnmconvol</H1> -Updated: 07 December 2009 +Updated: 03 January 2010 <BR> <A HREF="#index">Table Of Contents</A> @@ -24,7 +24,8 @@ pnmconvol - general MxN convolution on a Netpbm image <B>pnmconvol</B> <I>convolution_matrix_file</I> -[-nooffset] +[<b>-normalize</b> +[<b>-nooffset</b>] [<I>netpbmfile</I>] @@ -103,7 +104,7 @@ matrix has one weight for red, one for green, and one for blue. <pre> <tt> - -matrix=0,.2,0;.2,.2,..2;0,.2,0 + -matrix=0,.2,0;.2,.2,.2;0,.2,0 </tt> </pre> @@ -116,12 +117,18 @@ and is the weight to give to each component of a pixel that corresponds to that matrix location. <p>Note that when you supply this option via a shell, semicolon -(";") probably means something to the shell, so use quotation +(";") probably means something to the shell, so use quotation marks. <p>There is no way with this method to have different weights for different components of a pixel. +<p>The <b>-normalize</b> option is often quite handy with <b>-matrix</b> +because it lets you quickly throw together the command without working out the +math to make sure the matrix isn't biased. Note that if you use the +<b>-normalize</b> option, the weights in the matrix aren't actually the +numbers you specify in the <b>-matrix</b> option. + <h4 id="matrixfile">Regular Matrix File</h4> @@ -161,6 +168,9 @@ in the floating point numbers to do it. <p>There is no way to put comments in the file. There is no signature or any other metadata in the file. +<p>Note that if you use the <b>-normalize</b> option, the weights in the +matrix aren't actually what is in the file. + <h4 id="matrixpnm">PNM File</h4> @@ -272,6 +282,35 @@ a file and names that file. See <P>This option was new in Netpbm 10.49 (December 2009). Before that, use a PNM file for the convolution matrix. +<DT><B>-normalize</B> + +<dd>This option says to adjust the weights in your convolution matrix so they +all add up to one. You usually want them to add up to one so that the +convolved result tends to have the same overall brightness as the input. With +<b>-normalize</b>, <b>pnmconvol</b> scales all the weights by the same factor +to make the sum one. It does this for each plane. + +<p>This can be quite convenient because you can just throw numbers into +the matrix that have roughly the right relationship to each other and let +<b>pnmconvol</b> do the work of normalizing them. And you can adjust a matrix +by raising or lowering certain weights without having to modify all the other +weights to maintain normalcy. And you can use friendly integers. + +<p>Example: + +<pre> +<kbd> + $ pnmconvol myimage.ppm -normalize -matrix=1,1,1;1,1,1;1,1,1 +</kbd> +</pre> + +<p>This is of course a basic 3x3 average, but without you having to +specify 1/9 (.1111111) for each weight. + +<p>This option has no effect when you specify the convolution matrix +via pseudo-PNM file. + +<p>This option was new in Netpbm 10.50 (March 2010). <DT><B>-nooffset=</b> <DD>This is part of the obsolete PNM image method of specifying the |