pgmmorphconv



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




NAME

       pgmmorphconv - perform morphological convolutions: dilation, erosion



SYNOPSIS

       pgmmorphconv  [  -erode | -dilate | -open | -close ] templatefile [pgm-
       file]

       Minimum unique abbreviation of option is acceptable.  You may use  dou-
       ble  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: dila-
       tion and erosion.

       pgmmorphconv performs a "topological" convolution.  For each  pixel  of
       the input, pgmmorphconv generates an output pixel in the same position.
       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  sim-
       plest  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
       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 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 pnmconvol, 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, and 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 dila-
       tion, 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 2002    Pgmmorphconv User Manual(0)

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