How to count patches on a matrix?

Hi, I have a matrix (img_interp) 512x512, which is rebuilt using some patches (p) 5x5. Now, I want to count the number of overlapping patches on the main matrix (img_interp). How can I do? the code is below

clear all

% image creation
N = 100;
dr = 5; dc = 5;  %displacements
pr = 100; pc = 100;  %positions
x = zeros(512,512); x(pr+(1:N),pc+(1:N))=255*ones(N,N);
img1 = x;
x = zeros(512,512); x(pr+dr+(1:N),pc+dc+(1:N))=255*ones(N,N);
img2 = x;

% Calculation UV    
uv=calcolaOF(img1, img2);
u=uv(:,:,1);
v=uv(:,:,2);
% plot motion vector
%figure, quiver(u, v, 'color', 'b', 'linewidth', 5);
% set(gca,'YDir','reverse');
% title('Flow Vector','color','red');

count = zeros(size(img1));   % count patch contributions to individual pixels
[Nrow, Ncol] = size(img1);  
img_interp = zeros(size(img1)); % interpolated frame
dim_filtro=7; 
Np = 5;                     % patch size

skip = 2; % skip between patches
uvm=zeros(size(uv));
% ciclo sulle patch
for i=1:skip:Nrow-Np+1
    for j=1:skip:Ncol-Np+1   %2 cicli for per iterare ciascun patch
        p = img1(i+(0:Np-1),j+(0:Np-1));    % patch img1

          uvp = uv(i+(0:Np-1),j+(0:Np-1),:);    %patch matrix uv
          %riga 56 = riga 55 + riga 54
          uvm = VectorMedianFilterP(uvp, dim_filtro);  
          um=uvm((Np+1)/2,(Np+1)/2 , 1);  
          vm=uvm((Np+1)/2,(Np+1)/2 , 2); 

     % interpolation

    [X,Y] = meshgrid(0:Np-1);  % grid for original patch
    [Xdr,Ydc] = meshgrid(0:Np-2) ; % grid for new patch

    X=X+(um/2);
    Y=Y+(vm/2);       

    p_int= interp2(X,Y,p,Xdr, Ydc );

% insertion patches on img_interp

img_interp( i+(0:Np-2),j+(0:Np-2) ) = img_interp(i+(0:Np-2),j+(0:Np-2) ) + p_int;

%CHECK count 
if img_interp( i+(0:Np-2),j+(0:Np-2) )
count = count + 1;
end 

     end
   end

I don't know how to write the last part of the code Thanks

[jonas]

Undefined function or variable
'calcolaOF'.

Can you post a working example or explain in more detail what you are doing?