%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% preprocessing for the fingerprint identification
% written by zhang_rui at Chinese Academy of Science
% E-mail:zhangrui05@mails.gucas.ac.cn
% 2006/6/3
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

function [Y]=preprocessing(A);
[M,N]=size(A);
if (mean(A)<=10)
    valve=graythresh(A);
else
    valve=255*graythresh(A);
end
%--------------------------------------------------------------------------
%Perform two-dimensional median filtering 
A=medfilt2(A,[5,5]);
%figure;
%imshow(A,[]);
%--------------------------------------------------------------------------
%Perform Wiener filter 
A=wiener2(A);
%figure;
%imshow(A,[]);
%--------------------------------------------------------------------------
%gray to logical
%for i=1:M
 %   for j=1:N
  %      if(A(i,j)>valve)
   %         A(i,j)=1;
   %    else
   %         A(i,j)=0;
   %    end
   % end
   %end
A=~im2bw(A,0.6*graythresh(A));
%figure;
%imshow(A,[]);
%--------------------------------------------------------------------------
%skeletonization the picture
%A=not(A);
A=bwmorph(A,'skel',Inf);
%figure;
%imshow(A,[]);
A=bwmorph(A,'spur',2);
%figure;
%imshow(A,[]);
Y=A;