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?

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

Answer 1

[Joseph Cheng]

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

[Image Analyst]

kernel =  [1 1 1;1 1 1;1 1 1]/9 ;
averageImage = conv2(double(grayImage), kernel, 'same');
imshow(averageImage, []);

[Sibin Prasad]

Thank you Joseph Cheng. I think your answer might have worked. But I need do to the following (below image). So can you tell me how to the step 2. I think the idea you have provided me is enough for step 1. How can I do step 2 also. Thank You.

[Mohammed Abdul Wadood]

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