LSB密写分析-GPC分析

实现如下：

image='ste_cover.bmp';
ste_cover=imread(image);
[row,col]=size(ste_cover);

%计算穿过平面簇p0_num,p1_num总次数。
p0_num=0;
p1_num=0;
min_num=0;
max_num=0;
temp0=0;
temp1=0;
for i=1:row
    for j=1:col
        if((i<row)&&(j<col))
            %计算行方向的值
            min_num=min(ste_cover(i,j),ste_cover(i,j+1));
            max_num=max(ste_cover(i,j),ste_cover(i,j+1));
            %判断更小的值是奇数还是偶数
            if(mod(min_num,2)==0) 
                %为奇数时
                %计算p0_num
                temp0=min_num+1.5;
                while temp0<max_num
                    p0_num=p0_num+1;
                    temp0=temp0+2;
                end
                %计算p1_num
                temp1=min_num+0.5;
                while temp1<max_num
                    p1_num=p1_num+1;
                    temp1=temp1+2;
                end
            else
                %为偶数时
                temp0=min_num+0.5;
                while temp0<max_num
                    p0_num=p0_num+1;
                    temp0=temp0+2;
                end
                %计算p1_num
                temp1=min_num+1.5;
                while temp1<max_num
                    p1_num=p1_num+1;
                    temp1=temp1+2;
                end
            end
            %计算列方向的值
            min_num=min(ste_cover(i,j),ste_cover(i+1,j));
            max_num=max(ste_cover(i,j),ste_cover(i+1,j));
            %判断更小的值是奇数还是偶数
            if(mod(min_num,2)==0) 
                %为奇数时
                %计算p0_num
                temp0=min_num+1.5;
                while temp0<max_num
                    p0_num=p0_num+1;
                    temp0=temp0+2;
                end
                %计算p1_num
                temp1=min_num+0.5;
                while temp1<max_num
                    p1_num=p1_num+1;
                    temp1=temp1+2;
                end
            else
                %为偶数时
                %计算p0_num
                temp0=min_num+0.5;
                while temp0<max_num
                    p0_num=p0_num+1;
                    temp0=temp0+2;
                end
                %计算p1_num
                temp1=min_num+1.5;
                while temp1<max_num
                    p1_num=p1_num+1;
                    temp1=temp1+2;
                end
            end   
        else 
            if((j==col)&&(i<row))  
                %计算列方向的值
                min_num=min(ste_cover(i,j),ste_cover(i+1,j));
                max_num=max(ste_cover(i,j),ste_cover(i+1,j));
                %判断更小的值是奇数还是偶数
                if(mod(min_num,2)==0) 
                    %为奇数时
                    %计算p0_num
                    temp0=min_num+1.5;
                    while temp0<max_num
                        p0_num=p0_num+1;
                        temp0=temp0+2;
                    end
                    %计算p1_num
                    temp1=min_num+0.5;
                    while temp1<max_num
                        p1_num=p1_num+1;
                        temp1=temp1+2;
                    end
                else
                    %偶数的时候干的活
                    %计算p0_num
                    temp0=min_num+0.5;
                    while temp0<max_num
                        p0_num=p0_num+1;
                        temp0=temp0+2;
                    end
                    %计算p1_num
                    temp1=min_num+1.5;
                    while temp1<max_num
                        p1_num=p1_num+1;
                        temp1=temp1+2;
                    end
                end   
            end
            if((i==row)&&(j<col))
                %计算行方向的值
                min_num=min(ste_cover(i,j),ste_cover(i,j+1));
                max_num=max(ste_cover(i,j),ste_cover(i,j+1));
                %判断更小的值是奇数还是偶数
                if(mod(min_num,2)==0) 
                    %为奇数时
                    %计算p0_num
                    temp0=min_num+1.5;
                    while temp0<max_num
                        p0_num=p0_num+1;
                        temp0=temp0+2;
                    end
                    %计算p1_num
                    temp1=min_num+0.5;
                    while temp1<max_num
                        p1_num=p1_num+1;
                        temp1=temp1+2;
                    end
                else
                    %为偶数时
                    temp0=min_num+0.5;
                    while temp0<max_num
                        p0_num=p0_num+1;
                        temp0=temp0+2;
                    end
                    %计算p1_num
                    temp1=min_num+1.5;
                    while temp1<max_num
                        p1_num=p1_num+1;
                        temp1=temp1+2;
                    end
                end 
            end 
        end  
    end
end

R=p1_num/p0_num;
fprintf('R=%f\n',R);