a1.m

用数理统计上的T检测检验图象中是否隐藏有秘密信息

clear;
close all;
I=imread('cameraman.tif');
I1=double(I);
figure,imagesc(I1);
colormap(gray);
title('original image');

J0=bitget(I1,1);
figure,imagesc(J0);
colormap(gray);
title('original bit0');
J1=bitget(I1,2);
figure,imagesc(J1);
colormap(gray);
title('original bit1');

[m,n]=size(J0);
c=15;
res=zeros(256,58081);
mm1=1;
for i=1:m-c
   for j=1:n-c
    Jaa=imcrop(J1,[i,j,15,15]);
    J10=Jaa(:);
    res(1:256,mm1)=J10;
    mm1=mm1+1;
    j=j+1;
    end
i=i+1;
end 

Ta=zeros(1,58081);
for p=1:58081
    Lie=res(1:256,p);
    Lie_Z=Lie';
    [k,s]=size(Lie_Z);
    Ling=zeros(1,240);
    for x=1:s-16
        Yi_Huo=xor(Lie_Z(x),Lie_Z(x+16));
        Ling(1,x)=Yi_Huo;
        x=x+1;
    end
    yi_huo=Ling';
    He=sum(yi_huo);
    T=(2/sqrt(240))*(120-He);
    Ta(1,p)=T;
    p=p+1;
end
T1=Ta;
T2=T1';
T_A=mean(T2);
S=std(T2);
TT=(T_A/S)*sqrt(58081)
plot(Ta,'k');
axis([0 60000 -5 12]);
xlabel('The sequence number of window','fontsize',18);
ylabel('The value of statistical variable T','fontsize',18);
set(gca,'fontsize',18);