Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
Pgmmorphconv User Manual(0)			   Pgmmorphconv	User Manual(0)

       pgmmorphconv - perform morphological convolutions: dilation, erosion

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

       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.

       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 -di-

       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).







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


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


	       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)

       Luuk van	Dijk, 2001.

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

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

netpbm documentation		 29 March 2015	   Pgmmorphconv	User Manual(0)


Want to link to this manual page? Use this URL:

home | help