sliding window operation in image

I have an image of size 256*256, i want to use 3*3 window which slides over image and change the value of central pixel as sum of neighbouring 8 pixels. Please Help.

Answer 1

[Image Analyst]

Try conv2(), imfilter(), nlfilter(), or, if you want to move in "jumps" instead of by one pixel, blockproc().

[VIJENDRA]

thanks for your reply and i see the function usage of above said function but if my function is:

function y=shannon_entro(x)
       [M,N]=size(x);
       y=zeros(1,N);
       for l=1:N
          y(l) = -( sum(x(:,l).*log(x(:,l))) );
       end

then how can i implement it in 3*3 manner in image using above functions.

[VIJENDRA]

one can use nlfilter or blockprop.

[Image Analyst]

Sorry, for some reason I didn't see your follow up question from June until now. Please see my demo of nlfilter where you can have it perform your own custom operation/filter on the window at each location.