%Caculate MI of a and b in the region of the size(a)

function [mi] = EMI(a,b)
%
[M,N] = size(a);
% change a, b to range 1:n
if min(a(:))<1
    a = a-min(a(:))+1;
end
if min(b(:))<1
    b = b-min(b(:))+1;
end
    

% ncolora = max(a(:))-min(a(:))+1;
% ncolorb = max(b(:))-min(b(:))+1;
ncolora = max(a(:));
ncolorb = max(b(:));

hab = zeros(ncolora,ncolorb);
ha = zeros(1,ncolora);
hb = zeros(1,ncolorb);

%count begins
[M,N]=size(a);
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

%cal ha,hb,hab
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;
% cal EMI
% feature efficiency coefficient
n =2/5;
if Hab ~= 0
    e = (mi^n) / ( Hab^(1-n));
else% not usual happen, just for test
    e = -1;%(mi^n) / ( Hab^(1-n)+1e-10);
end
mi = e;
% %