From 1017cbebe5d5edd859e0fddad0a8600f509f4821 Mon Sep 17 00:00:00 2001 From: giraffedata Date: Mon, 25 Dec 2006 03:06:05 +0000 Subject: Place user guide into Subversion repository git-svn-id: http://svn.code.sf.net/p/netpbm/code/userguide@181 9d0c8265-081b-0410-96cb-a4ca84ce46f8 --- pbmtopgm.html | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) create mode 100644 pbmtopgm.html (limited to 'pbmtopgm.html') diff --git a/pbmtopgm.html b/pbmtopgm.html new file mode 100644 index 00000000..f68dfcad --- /dev/null +++ b/pbmtopgm.html @@ -0,0 +1,84 @@ + +Pbmtopgm User Manual + + +

pbmtopgm

+

Updated: 05 Feb 2003 + +Table Of Contents + +  +

NAME

+pbmtopgm - convert PBM image to PGM by averaging areas + +  +

SYNOPSIS

+ +pbmtopgm +width +height +[pbmfile] + +  +

DESCRIPTION

+ +

This program is part of Netpbm. + +

pbmtopgm reads a PBM image as input. It outputs a PGM image +in which each pixel's gray level is the average of the surrounding +black and white input pixels. The surrounding area is a rectangle of +width by height pixels. + +

In other words, this is a convolution. pbmtopgm is similar +to a special case of pnmconvol. + +

You may need a pnmsmooth step after pbmtopgm. + +

pbmtopgm has the effect of anti-aliasing bitmaps which +contain distinct line features. + +

pbmtopgm works best with odd sample width and heights. + +

You don't need pbmtopgm just to use a PGM program on a PBM +image. Any PGM program (assuming it uses the Netpbm libraries to read +the PGM input) takes PBM input as if it were PGM, with only the +mininum and maximum gray levels. So unless your convolution rectangle +is bigger than one pixel, you're not gaining anything with a +pbmtopgm step. + +

The opposite transformation (which would turn a PGM into a PBM) is +dithering. See pamditherbw. + +  +

SEE ALSO

+ +pamditherbw, +pnmconvol, +pbm, +pgm + +  +

AUTHOR

+ +

Copyright (C) 1990 by Angus Duggan. +

Copyright (C) 1989 by Jef Poskanzer. + +

Permission to use, copy, modify, and distribute this software and +its documentation for any purpose and without fee is hereby granted, +provided that the above copyright notice appear in all copies and that +both that copyright notice and this permission notice appear in +supporting documentation. This software is provided "as is" +without express or implied warranty. + +

+  +

Table Of Contents

+ + + -- cgit 1.4.1