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function [T]=t_autoset(I) 
%自动确定图象阈值 
%I=imread('eye.jpg') 
graycount=imhist(I); 
sz=size(I); 
T=0; 
 
graycount=filter([0.5 0 0.5],1,graycount);% 邻域平均滤波,平滑灰度曲线 
%figure,imhist(I); 
%figure,stem([0:255],graycount,'marker','none'); 
%差分法求导 
diff_cnt=diff(graycount); 
 
pre_max = graycount(1);%阈值之前的峰值 
for i = 2 : (length(diff_cnt)-1) 
    if (graycount(i)>graycount(i-1))&(graycount(i+1)0)&(diff_cnt(i+1)<0) 
        %极大值点 
        pre_max=max(graycount(i),pre_max); 
        continue; 
    end 
    if (graycount(i)graycount(i))&(diff_cnt(i-1)<0)&(diff_cnt(i+1)>0)&(graycount(i)<0.75*pre_max)&(pre_max/(sz(1)*sz(2))>0.0025) 
        %极小值点 
        %且阈值点的像素数应小于此前出现的峰值点值的3/4，且这个峰值点的像素数大于总像素数的0.0025 
        T=i; 
        break; 
    end 
end