% fig921.m : figure 9.21 in Gonzales and Wood, pp. 542
% (C) 2003 by Yu Hen Hu
% created: 12/1/2003
% call hitnmiss.m
% note that masks are represented by +1, -1 and 0 (don't care)

clear all
A = [1 1 1 1 1 1 1 1 1 1 1
   1 1 1 1 1 1 1 1 1 0 0
   1 1 1 1 1 1 1 1 1 0 0
   1 1 1 1 1 1 1 1 1 0 0
   1 1 1 0 0 1 1 1 1 0 0];
[m,n]=size(A);

B{1}=[-1 -1 -1; 0 1 0 ; 1 1 1];
B{2}=[0 -1 -1 ;1 1 -1; 1 1 0];
B{3}=[1 0 -1;1 1 -1;1 0 -1];
B{4}=[1 1 0;1 1 -1; 0 -1 -1];
B{5}=[1 1 1;0 1 0;-1 -1 -1];
B{6}=[0 1 1;-1 1 1;-1 -1 0];
B{7}=[-1 0 1;-1 1 1;-1 0 1];
B{8}=[-1 -1 0;-1 1 1;0 1 1];

x0=A; x=x0; 
figure(1),clf,colormap('gray')
subplot(121),imagesc(ones(m,n)-A);
converged=0; iter=0;
while converged==0,
   iter=iter+1;
   for i=1:8,
      x=x-hitnmiss(x,B{i});
      subplot(122),imagesc(ones(m,n)-x);
      disp(['B' int2str(i) ' applied, press any key to continue ... '])
      pause
   end
   disp(['********  # of passes = ' int2str(iter)]);
   if sum(sum(x0-x))==0, 
      converged=1; 
      disp('converged!');
   else x0=x; end
end