Manual median filter design

Hello, I want to implement a simple median filter of window size '5' manually.I found a thread here

medain with blockpro(),nlfilter but when I tried with the help blockpro() and nlfilter() both showed nlfilter() and blockpro() not found. I don't have imageprocessing toolbox.

So,can anyone help me out in implementing the median filter manually.

Answer 1

[Anand]

Well if you don't have the Image Processing Toolbox, I'm afraid you won't be able to use blockproc. In that case, you would have to resort to something like this:

imout = zeros(size(im),class(im));
for m = 3 : size(im,1)-2
    for n = 3 : size(im,2)-2
        list = im(m-2:m+2,n-2:n+2);
        imout(m,n) = median(list(:));
    end
end

Note that this is the most naive way to do it. There are lots of better ways to do it, but this is the easiest to understand.

[Image Analyst]

Right, good point - I keep forgetting that blockproc() is in that toolbox. It seems so general that I always think it's in base MATLAB, but it's not.

Answer 2

[Image Analyst]

See my blockproc() demos (attached below in blue). Demo1 does the median. Demo2 does a custom filter, like you'd do with nlfilter(). Note: blockproc() normally moves in "jumps" of the window size. To get it to move over just one pixel instead of the whole window width, you'll need to adjust the 'Bordersize' option of blockproc().