定位篡改位置所在的子块

在图像处理中为了处理上的方便经常需要对图像进行分块，分块后需要对整块进行处理。

此处给出了两种定位篡改块的处理方式。

lilizong【at】gmail

方式1：直接对所在块操作。

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clear;
clc;
key1=32;
key2=32;
A=imread('../image/hetong.bmp');
V=imread('../image/2.bmp');
A=im2bw(A);
V=im2bw(V);
[m,n]=size(A);
AC=cell(key1,key2);%将图像分为8*8的块
mkey1=floor(m/key1);
nkey2=floor(m/key2);
for i=1:mkey1
    for j=1:nkey2
        AC{i,j}=A((i-1)*key1+1:i*key1,(j-1)*key2+1:j*key2);
    end
end
VC=cell(key1,key2);%将图像分为8*8的块
for i=1:mkey1
    for j=1:nkey2
        VC{i,j}=V((i-1)*key1+1:i*key1,(j-1)*key2+1:j*key2);
    end
end
a=zeros(key1,key2);
%用来作为临时数组，保存从每个8*8块中提取出来的数值
B=zeros(mkey1,nkey2);
%用来存放8*8分块的均值
for i=1:(mkey1)
    for j=1:(nkey2)
        a=AC(i,j);
        ab=cell2mat(a);
        %取得当前的块，并将之转化
        w=0;
        for ii=1:key1
            for jj=1:key2
                w=w+ab(ii,jj);
            end
        end
        v=VC(i,j);
        av=cell2mat(v);
        %取得当前的块，并将之转化
        w2=0;
        for ii=1:key1
            for jj=1:key2
                w2=w2+av(ii,jj);
            end
        end
        if w~=w2

            B(i,j)=0;
        else
            B(i,j)=1;
        end
    end
end
subplot(1,3,1),imshow(A);
set(gca,'Title',text('String','原始图像'))
subplot(1,3,2),imshow(V);
set(gca,'Title',text('String','篡改图像'))
subplot(1,3,3),imshow(B,[]);
set(gca,'Title',text('String',[num2str(key1),'*',num2str(key2),'定位图像']))

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方式2：直接将分块处理为一个像素，然后再对定位图像进行缩放。

A=imread('../image/hetong.bmp');
V=imread('../image/2.bmp');
av=xor(A,V);
A=av;
figure,imshow(av);
key1=8;
key2=8;
mkey1=512/key1;
nkey2=512/key2;
B=cell(key1,key2);%将图像分为8*8的块
for i=1:mkey1
    for j=1:nkey2
        B{i,j}=A((i-1)*key1+1:i*key1,(j-1)*key2+1:j*key2);
    end
end
a=zeros(key1,key2);
%用来作为临时数组，保存从每个8*8块中提取出来的数值
averageB=zeros(mkey1,nkey2);
%用来存放8*8分块的均值
for i=1:(mkey1)
    for j=1:(nkey2)
        b=B(i,j);
        b=cell2mat(b);
        %取得当前的块，并将之转化
        w=0;
        for ii=1:key1
            for jj=1:key2
                if b(ii,jj)==1
                    w=100;
                end
            end
        end

        if w==100
            averageB(i,j)=0;
        else
            averageB(i,j)=255;
        end
    end
end
w=imresize(averageB,key1);
figure,imshow(w,[]);
w=double(w);
imwrite(w,'../image/re.bmp');