How to reduce for loops in a moving window based operation?

How to reduce for loops in a moving window based operation? I'm using a 15x15 window across two images and performing multiplication to get average value per pixel.

win1=15;
pp=1;qq=1;
  [ma,na]=size(g); g represents an image
  z= (win1 -1)/2;%centre of window
  ini=z+1;
   for i= ini :(ma-z)
       for j= ini:(na-z)
            for a= (i-z):(i+z)  
                for b=(j-z):(j+z)
                    W(pp,qq)= g(a, b);%window on image
                    Es(pp,qq)=edg(a,b);%window on image containing edges
                    qq=qq+1;
                end
                qq=1;
                pp=pp+1;
            end 
            pp=1;
     E(i,j)=sum(sum(W.*Es))/sum(sum(Es));
       end
    end

[Jan]

I cannot read the attached image, because the indices are simply too small. The posted code does not run. What is: ini, ma, z, na, pp, qq initially? index is not used anywhere. What is g() and edg()?

[dpb]

Insufficient time to read closely enough, but look at

doc blockproc % image toolbox
doc filter2

[h612]

@Jan Simon the question is edited with more info. pp and qq are initialized at 1;

[Jan]

@h612: Are they? Where? What is g and win1?

[h612]

@Jan Simon, kindly refer to the code now.

Answer 1

[Jan]

Based on some guessing:

[ma,na] = size(g);
z   = (win1 -1)/2;%centre of window
ini = z+1;
E   = zeros(ma-z, na-z);  % Pre-allocate!!!
for i = ini:(ma-z)
   for j = ini:(na-z)
      W      = g((i-z):(i+z), (j-z):(j+z));
      Es     = edg((i-z):(i+z), (j-z):(j+z));
      E(i,j) = sum(sum(W .* Es)) / sum(sum(Es));
      % Faster:
      % E(i,j) = (W(:).' * Es(:)) / sum(Es(:));
   end
end

Here the element W(i1,i2) is multiplied 2*z times with Es(i1,i2). This is a waste of time. What about starting with:

S = g .* edg;

and then dividing the moving sum of S by the moving sum of edg? This would be the filter2 approach suggested by dpb.

S = g .* edg;
M = ones(z, z);
E = filter2(M, S, 'same') ./ filter2(M, edg, 'same');

This code is not tested and it thought as a demonstration only. Adjust it to you your needs.