Pgmmorphconv User Manual(0)         Pgmmorphconv User Manual(0)



Table Of Contents


NAME
       pgmmorphconv - perform morphological convolutions: dila-
       tion, erosion


SYNOPSIS
       pgmmorphconv [ -erode | -dilate | -open | -close ]  tem-
       platefile [pgmfile]

       Minimum  unique  abbreviation  of  option is acceptable.
       You may use double hyphens 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(1).

       pgmmorphconv performs morphological  convolutions  on  a
       PGM image: dilation and erosion.

       pgmmorphconv  performs a "topological" convolution.  For
       each pixel of the input, pgmmorphconv generates an  out-
       put pixel in the same position.  To determine the inten-
       sity 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.   pgm-
       morphconv  looks  at  the  input  pixels underneath each
       white pixel in the template.  For a dilation, the  maxi-
       mum  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  identi-
       cal  to  the  input.  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 num-
       ber  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
       pnmconvol, except that with pnmconvol the output  inten-
       sity  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 ero-
       sion 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 -dilate.


SEE ALSO
       pgmminkowski(1) pnmconvolz(1) pgm(1)


AUTHORS
       Luuk van Dijk, 2001.

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



netpbm documentation    29 October 2Pgmmorphconv User Manual(0)
