I need to create a 3 by 3 window and calculate mean within the window. This window is to move through the image. How can I do it?

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Sibin Prasad
Sibin Prasad on 6 Apr 2017
I am new to MATLAB. This is what I have done. I got this from here and there online. Is there an efficient way of doin it?
Thank you
for i = side:p
for j = side:q
nhood_ctr = [i j];
nhood = im3((nhood_ctr(1)-floor(side/2)):(nhood_ctr(1)+floor(side/2)),(nhood_ctr(2)-floor(side/2)):(nhood_ctr(2)+floor(side/2)));
%size(nhood)
avg(i,j) = mean(mean(nhood));
sum = 0;
for k = (nhood_ctr(1)-floor(side/2)):(nhood_ctr(1)+floor(side/2))%i-2:i+2
for l = (nhood_ctr(2)-floor(side/2)):(nhood_ctr(2)+floor(side/2))%j-2:j+2
x = im3(k,l)- avg(i,j);
sum = sum + x*x;
end
end
igvm(i,j) = sum;
end
end

Answers (1)

Joseph Cheng
Joseph Cheng on 6 Apr 2017
I would take a look at the conv() and conv2() function. you would use something like [1 1 1;1 1 1;1 1 1]/9 to get mean. and then probably select 'same' or valid depending on how you want to treat the edges of the image
  3 Comments
Mohammed Abdul Wadood
Mohammed Abdul Wadood on 13 May 2022
I have question please @Image Analyst , your answer above
kernel = [1 1 1;1 1 1;1 1 1]/9 ;
averageImage = conv2(double(grayImage), kernel, 'same');
imshow(averageImage, []);
it is for calculate the average within the window, but what if I want to calculate euclidean distance insted of average, how can i solve this?
another quastion please, why you use (double) in
averageImage = conv2(double(grayImage), kernel, 'same');
if I split the image to (R, G & B) channel which it is gray channels, can I avoid (double)?
and the last question, what the purpose from ( [ ] ) in (imshow) step
imshow(averageImage, []);
sorry for annoyance and thank you so much

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