大津阈值分割法.docx

clc
clear
y=imread('mat4.ico');
a=rgb2gray(y);
L=256;
Ps = zeros(L,1);
nk=zeros(L,1);
[row,col]=size(y);
n=row*col;
for i = 1:row
for j = 1:col
num = double(y(i,j))+1;
nk(num) = nk(num)+1; end
end
for i=1:L
Ps(i)=nk(i)/n;
end
%figure(4),imhist(hist);
%p=imhist(hist);
figure
imshow(a)
count=imhist(a);
[m,n]=size(a);
A=m*n;
L=256;
count=count/A;
for i=1:L
if count(i)~=0
st=i-1;
break;
end
end
for i=L:-1:1
if count(i)~=0
nd=i-1;
break;
end
end
f=count(st+1:nd+1);
p=st; q=nd-st;
u=0;
for i=1:q
u=u+f(i)*(p+i-1);
ua(i)=u;
end;

for i=1:q
w(i)=sum(f(1:i));
end;

d=(u*w-ua).^2./(w.*(1-w));
[y,tp]=max(d);
th=tp+p;
for i=1:m
for j=1:n
if a(i,j)>th
a(i,j)=255;
else
a(i,j)=0;
end
end
end
figure
imshow(a);

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