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?

2 views (last 30 days)
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)));
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;
igvm(i,j) = sum;

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
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

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!