Circular patch using COLFILT?

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?

Answer 1

[Sean de Wolski]

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))

Answer 2

[Image Analyst]

To do that, (max-min), it looks like you can use rangefilt().

[Sean de Wolski]

Yeah, actually:

F = floor(rangefilt(I,getnhood(strel('disk',r)))./r)