%fig917.m - Figure 9.17 Gonzales and Woods' book
% connected component extraction example
% (C) 2003 by Yu Hen Hu
% created: 12/2/2003

clear all

A=[0 0 0 0 0 0 0 0 0 0
   0 0 0 0 0 0 1 1 1 0
   0 0 0 0 0 0 1 1 1 0
   0 0 0 0 0 1 1 0 1 0 
   0 0 0 0 0 1 1 1 1 0
   0 0 0 1 1 1 0 0 0 0
   0 0 1 1 1 0 0 0 0 0
   0 1 0 0 1 0 0 0 0 0 
   0 0 1 1 1 0 0 0 0 0
   0 0 0 0 0 0 0 0 0 0];
figure(1),clf,colormap('gray')
subplot(131),imagesc(A),

x=zeros(size(A)); x(7,4)=1; 
B=ones(3);
k=0;
converged=0;
while converged==0, 
   k=k+1;
   subplot(132),imagesc(x),
   xnew=double(and(dilate(x,B),A));
   if sum(sum(xnew-x))==0,
      converged=1;
   end
   disp(['iteration # ' int2str(k)]);
   x=xnew;
   pause(1)
end
subplot(133),imagesc(x),title('extracted connected component')