pgmmorphconv

   Updated: 29 October 2002
   Table Of Contents

NAME

   pgmmorphconv	 -  perform morphological convolutions: dilation,
erosion

SYNOPSIS

   pgmmorphconv [ -erode | -dilate | -open | -close  ]	template-
file [pgmfile]

   Minimum  unique  abbreviation of option is acceptable. You may
use double
   hypens instead of single hyphen to denote options. You may use
white space
   in  place  of  the equals sign to separate an option name from
its value.

DESCRIPTION

   This program is part of Netpbm.

   pgmmorphconv performs morphological convolutions on a PGM  im-
age: dilation
   and erosion.

   pgmmorphconv	 performs  a  "topological" convolution. For each
pixel of the
   input, pgmmorphconv generates an output pixel in the same  po-
sition. To
   determine the intensity of the output pixel, pgmmorphconv lays
the template
   image over the input image such that the middle pixel  of  the
template is
   over	 the  input  pixel in question. pgmmorphconv looks at the
input pixels
   underneath each white pixel in the template. For  a	dilation,
the maximum
   intensity  of  all those pixels is the intensity of the output
pixel. For an
   erosion, it is the minimum.

   Thus, the dilation effect is that bright areas  of  the  input
get bigger and
   dark	  areas	 smaller. The erosion effect is the opposite. The
simplest
   template image would be one with a white pixel in  the  middle
and the rest
   black. This would produce an output image identical to the in-
put. Another
   simple template image is a fully  white  square.  This  causes
bright or dark
   areas  to  expand  in all directions. A template image that is
white on the
   left side and black on the right would smear the image to  the
right.

   The	template file named by templatefile contains the template
image as a PBM
   image. It must have an odd number of rows and an odd number of
columns, so
   there is a definite middle pixel. It must contain at least one
white pixel.

   This is similar to the continuous convolution done by  pnmcon-
vol, except that
   with	 pnmconvol  the output intensity is a weighted average of
nearby input
   pixels instead of a minimum or maximum.

   This convolution changes the three Minkowski	 integrals  in	a
predefined way,
   an can be used to filter an image to enhance certain features,
to ease their
   automatic recognition.

   The options -erode and -dilate obviously produce an erosion or
dilation,
   respectively.

   The -open option causes pgmmorphconv to perform first an erode
and then a
   dilate operation. The -close option causes a dilate first  and
then an erode.
   If  you  specify none of these options, it is the same as -di-
late.

SEE ALSO

   pgmminkowski pnmconvolz pgm

AUTHORS

   Luuk van Dijk, 2001.

   Based on work  which	 is  Copyright	(C)  1989,  1991  by  Jef
Poskanzer.
     _________________________________________________________________



Table Of Contents

     * NAME
     * SYNOPSIS
     * DESCRIPTION
     * SEE ALSO
     * AUTHORS

UNIX/Linux commands referenced on this page:

1. at
2. expand
3. file
4. as
5. pnmconvol
6. pgmminkowski