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Re: 2-D Convolutions in IDL w/o zero-padded edges [message #56396 is a reply to message #56391]

Tue, 23 October 2007 14:50

Jean H.
Messages: 472
Registered: July 2006

Senior Member

Matt Harner wrote:
> Hello.
>
> I am familiar with IDL and convolutions independently but not
> together. Is there a way in IDL to convolve an image with a kernal
> and return only those parts of the convolution that are computed
> without zero-padded edges? This would be equivalent to the MATLAB
> procedure conv2(image,kernel, 'valid').
>
> Thanks in advance for any help.
> Matt

Maybe you could compute the convolution over the whole area, then keep
only the valid entries... so if your kernel is a 3*3 one, you would do

GoodResults = AllResult[1:Xsize-2; 1:Ysize-2]

If you are using a kernel that is not a square, I have a function to
reduce your study area so that every pixel has a complete neighborhood
(you define the neighborhood by its coordinates as if it was centered on
cell 0;0)

Jean

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		Re: 2-D Convolutions in IDL w/o zero-padded edges By: Tal on Wed, 24 October 2007 01:56
		Re: 2-D Convolutions in IDL w/o zero-padded edges By: Jean H. on Tue, 23 October 2007 14:50

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