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1、创新课程课后作业多媒体信息安全及其应用学生姓名杨刚学号1416240318专业班级14级计算机科学与技术3班指导教师张秋余学院计算机与通信学院成绩实验作业一DCT变换域数字水印调试一、experiment1.m调试结果：原始图像原始水印图像置乱后的水印图像含水印的图像二、experiment2.m调试结果含水印的图像提取的水印图像恢复的水印图像三、experiment3.m调试结果原始水印图像提取的水印图像NC归一化相关系数=0.9341回答NC值的大小决定了什么因素？是不是NC值越大越好？NC的值决定了原始水印和提取出来的水印大的相似度，NC值越
2、大原始水印与提取出来的水印越相似。四、总结：数字水印是现代信号处理领域研究的热点之一,涉及图像处理、数字通信、密码学、信息安全等多学科领域,增强数字水印的鲁棒性是数字水印问题的关键。变换域技术，即把待隐藏的信息嵌入到载体的一个变换空间(如频域)中。变换域法具有可与数据压缩标准兼容的优点，对诸如压缩、剪裁和某些图像处理等攻击的鲁棒性更强。利用基于二维DCT的信息隐藏算法对图像进行的处理具有良好的安全性、不可感知性、鲁棒性和可证明性。它可以应用到静止图像水印、视频水印、版权保护、篡改提示、使用控制等领域中。在以图像为隐蔽载体的信息隐藏技术中有着广泛的应
3、用前景。附件：程序代码experiment1.m0%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%嵌入水印%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%clearcloseallW=imread('yanggang-watermark.bmp');%watermarkW应该为64*64的图像W=rgb2gray(W);W=im2bw(W,0.5);subplot(1,2,1);im
4、show(W);title('originalyanggang-watermark');W=Torus(W,20);%对W进行Torus变换函数待实现;subplot(1,2,2);imshow(W);title('yanggang-watermarkaftertorustransform');size1=size(W);M1=size1(1);M2=size1(2);w=zeros(1,M1*M2);forj=1:M1fori=1:M2w((i-1)*M1+j)=W(i,j);endend%将水印存入w中%%%%%%%%%%%%%%%%%%%%%
5、%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%55%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%I=imread('lena.jpg');%image256*256figure;subplot(1,2,1);imshow(I);title('originalimage');size2=size(I);N1=size2(1);N2=size2(2);n1=N1/8;n2=N2/8;fora=1:n1forb=1:n2f{a,b}=I(((a
6、-1)*8+1):(a*8),((b-1)*8+1):(b*8));F{a,b}=dct2(f{a,b});endend%将原图分成8*8的小块,共32*32块分别做dct变换%n=(64*M1*M2)/(N1*N2);%n=4???%Q=intensity(F);%求出每块图像里被选定区域的水印嵌入强度F=embed(F,Q,w);%将水印嵌入到选定的区域上每小块嵌入4bit的水印信息%I2=zeros(256,256);forn=1:N2/8form=1:N1/8f{m,n}=idct2(F{m,n}/255);I2((m*8-7):m*8,(
7、n*8-7):n*8)=f{m,n};endendsubplot(1,2,2);imshow(I2);%得到嵌入水印后的图像title('markedimage')imwrite(I2,'marked.bmp','bmp');savemarkedI2;Experiment2.m%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%提取水印%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
8、%%%%%%%%%%%%%%%%%%%%%%%%I2=imread('marked.bmp');figure;imshow
