% smooth an image

% define mask (odd by odd centered mask)
mask = [1,2,1;2,3,2;1,2,1];
mask = mask/sum(abs(mask(:)));

cmask = fliplr(flipud(mask));
[m,n] = size(mask);
pausetime = .01

% load image fragement
r0 = 50;
dr  = 64;
s0 = 50;
ds  = 64;
load clown
Y = X(r0:(r0+dr-1),r0:(s0+ds-1));
W = Y;
Z = Y;
mn = min(Y(:));
mx = max(Y(:));

%initial plot 

figure(1)
subplot(1,2,1)
imshow(Y,[mn,mx]);
title('original picture')
subplot(1,2,2)
imshow(Z,[mn,mx]);
title('smoothed picture')

pause
disp('Press a key to start');

brinds = mod((1:m)-(m+1)/2,dr)+1;  
bsinds = mod((1:n)-(n+1)/2,ds)+1; 
orinds = bsinds;
osinds = bsinds;
rinds = brinds;

for r = 1:dr
   sinds = bsinds; 
   for s = 1:ds
      W(orinds,osinds)=Y(orinds,osinds);
      sinds = mod(sinds,ds)+1;
      orinds = rinds;
      osinds = sinds;
      U  =  Y(rinds,sinds);
      W(rinds,sinds) =  mn;
      Z(r,s)= sum(U(:).*cmask(:));
      subplot(1,2,1)
      imshow(W,[mn,mx]);
      title('original picture and current pixels')
      subplot(1,2,2)
      imshow(Z,[mn,mx]);
      title('smoothed picture')
      pause(pausetime)   
   end
   rinds = mod(rinds,dr)+1;
end