NAME

       pgmmorphconv - perform morphological convolutions: dilation, erosion

SYNOPSIS

       pgmmorphconv [
        -erode |
        -dilate |
        -open |
        -close |
        -gradient ] templatefile [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 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 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 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.

OPTIONS

       In addition to the options common to all programs based on libnetpbm (most notably -quiet,
       see
        Common  Options  ⟨index.html#commonoptions⟩  ),  pgmmorphconv  recognizes  the  following
       command line options:

       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 -dilate.

       With  -gradient, pgmmorphconv produces an image which is the difference between the eroded
       image and the dilated image.  -gradient was new in Netpbm 10.70 (March 2015).

SEE ALSO

       •

              pgmminkowski(1)

       •

              pnmconvol(1)

       •

              pgm(1)

       For more information about morphological convolutions, see e.g.

       •

               J.S. Kole, K. Michielsen, and  H.  De  Raedt,  "Morphological  Image  Analysis  of
              Quantum  Motion  in  Billiards",  Phys.  Rev.  E  63,  016201-1  -  016201-7 (2001)
              ⟨http://rugth30.phys.rug.nl/pdf/prechaos.pdf⟩

       •      K. Michielsen and H. De Raedt, "Integral-Geometry  Morphological  Image  Analysis",
              Phys. Rep. 347, 461-538 (2001).

AUTHORS

       Luuk van Dijk, 2001.

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

DOCUMENT SOURCE

       This  manual page was generated by the Netpbm tool 'makeman' from HTML source.  The master
       documentation is at

              http://netpbm.sourceforge.net/doc/pgmmorphconv.html