Circular patch using COLFILT?

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Faraz
Faraz on 4 Nov 2013
Commented: Sean de Wolski on 4 Nov 2013
Hi there,
COLFILT operates a function on a matrix/image within a rectangular patch of [m n]. Instead of a rectangular one; I want my function to operate within a circular disc/mask. Is there a way to do it?
Example:
r = 5; % a certain length
rc = @(x) floor(((max(x)-min(x))/r))+ 1; % a non-linear filter
F= colfilt(I, [r r],'sliding', rc); % I is my 2D matrix/image
Query: Here, if I want to have a disk of radius r, instead of a rectangle [r r], how I do that?

Answers (2)

Sean de Wolski
Sean de Wolski on 4 Nov 2013
Inside of your anonymous function, you could use logical indexing to only apply the operation to the circular part of the rectangular. As for generating the circle, an easy way:
M = getnhood(strel('disk',r))

Image Analyst
Image Analyst on 4 Nov 2013
To do that, (max-min), it looks like you can use rangefilt().
  1 Comment
Sean de Wolski
Sean de Wolski on 4 Nov 2013
Yeah, actually:
F = floor(rangefilt(I,getnhood(strel('disk',r)))./r)

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