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Re: Erosion/Dilation Operators [message #8201]

Wed, 19 February 1997 00:00

Kirt Schaper
Messages: 6
Registered: February 1997

Junior Member

David Fanning wrote:
>
> Hi,
>
> Does anyone have any practical experience using the erosion
> and dilation operators in IDL? I can't make much sense of the
> documentation. In particular, I can't figure out what a good
> structuring element would be.

The way I think about it is that the structuring element (SE) is
like a kernel for a convolution. it is centered over each pixel
in the input image, and if all non-zero pixels in the SE are also
non-zero in the input image, then the pixel in the output image is
set.

The most common SE's are square (or circular) masks 'centered'
in the middle, e.g. replicate(1,3,3) or:

se = bytarr(5,5)
for i=0,4 do &
for j = 0,4 do &
if (sqrt((i-2)^2 + (j-2)^2) le 2) then &
se(i,j) = 1

Warning: non-symmetric and/or non-centered structuring elements
can lead to serious headaches.

-------------------------------------------------------
Kirt Schaper | Bell: (612) 725-2000 x4791
PET Center (11P) | net: kirt@pet.med.va.gov
VA Medical Center | FAX: (612) 725-2068
MPLS, MN 55417 | URL: http://pet.med.va.gov:8080

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[Message index]

		Re: Erosion/Dilation Operators By: Kirt Schaper on Wed, 19 February 1997 00:00
		Re: Erosion/Dilation Operators By: djackson on Wed, 19 February 1997 00:00
		Re: Erosion/Dilation Operators By: Christian Soeller on Wed, 19 February 1997 00:00
		Re: Erosion/Dilation Operators By: Achim Hein on Wed, 19 February 1997 00:00
		Re: Erosion/Dilation Operators By: Christian Soeller on Wed, 19 February 1997 00:00
		Re: Erosion/Dilation Operators By: Achim Hein on Tue, 18 February 1997 00:00

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