function [eval1]=fitness(x,popsize,stringlength)
%      A=imread('pout.tif');
%      load woman;
%      A=imread('blood1.tif');
      A=imread('rice.tif');
% my=imread('mysaturn.tif');
% A=wiener2(my,[5 5]);
     a=imread('mytu.tif');
     A=rgb2gray(a);
     count=imhist(A);
     [m,n]=size(A);
     N=m*n;
     L=256;
     count=count/N;     %各個灰度級出現(xiàn)的概率
     eval1=zeros(popsize,1);
%  for i=1:popsize
     u=0;
     for j=1:L
         u=u+count(j)*j;  %圖像的平均灰度
     end
     
     w=0;ua=0;	
%         xi=x(i);
     for j=1:x           
         w=w+count(j);    %區(qū)域1的平均灰度
         ua=ua+count(j)*j;
     end
     if (w==0)|(w==1)
         eval1=0;
     else
         eval1=(u*w-ua)^2/(w*(1-w));
     end
% end