www.gusucode.com > 《图像配准技术及其Matlab编程实现》--源码程序 > 《图像配准技术及其Matlab编程实现》/match/CalculateMI.m

    function mi=CalculateMI(a,b)
%参数：a：输入图像a
%     b：输入图像b
%     mi：图像a和b的互信息值
%功能：利用一个联合直方图，计算两幅图像的互信息值。
a=double(a);
b=double(b);
[M,N]=size(a);
hab=zeros(256,256);
pad=zeros(256,256);  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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;
for i=1:M
    for j=1:N
        index_x=a(i,j);
        index_y=b(i,j);
        hab(index_x,index_y)=hab(index_x,index_y)+1;
    end
end

habsum=sum(sum(hab));
index=find(hab~=0);
pab=hab/habsum;
Hab=sum(sum(-pad(index).*log2(pab(index))));

pa=sum(pab');
index=find(pa~=0);
Ha=sum(sum(-pa(index).*log2(pa(index))));
pb=sum(pab);
index=find(pb~=0);
Hb=sum(sum(-pb(index).*log2(pb(index))));

mi=Ha+Hb-Hab


%CalculateMI('line.bmp','lena.bmp');