www.pudn.com > 1111111registrationbasedoncorrelation.rar > MI.m

%Caculate MI of a and b in the region of the size(a) 
 
function mi = MI(a,b) 
% 
[M,N] = size(a); 
 
hab = zeros(256,256); 
ha = zeros(1,256); 
hb = zeros(1,256); 
 
if max(max(a))~=min(min(a)) 
    a = (a-min(min(a)))/(max(max(a))-min(min(a))); 
else 
    a = zeros(M,N); 
end 
  
if max(max(b))-min(min(b)) 
    b = (b-min(min(b)))/(max(max(b))-min(min(b))); 
else 
    b = zeros(M,N); 
end 
 
a = double(int16(a*255))+1; 
b = double(int16(b*255))+1; 
% a = int16(a)+1; 
% b = int16(b)+1; 
 
for i=1:M 
    for j=1:N 
       indexx =  a(i,j); 
       indexy = b(i,j) ; 
       hab(indexx,indexy) = hab(indexx,indexy)+1; 
       ha(indexx) = ha(indexx)+1; 
       hb(indexy) = hb(indexy)+1; 
   end 
end 
 
hsum = sum(sum(hab)); 
index = find(hab~=0); 
p = hab/hsum; 
Hab = sum(sum(-p(index).*log(p(index)))); 
 
hsum = sum(sum(ha)); 
index = find(ha~=0); 
p = ha/hsum; 
Ha = sum(sum(-p(index).*log(p(index)))); 
 
hsum = sum(sum(hb)); 
index = find(hb~=0); 
p = hb/hsum; 
Hb = sum(sum(-p(index).*log(p(index)))); 
 
mi = Ha+Hb-Hab;