DCT.rar_DCT 水印_dct_dct matlab_matlab DCT_二维图像 DCT

%整理自lufei的水印代码（数字水印论坛） %整理：wyy022 %Project: Threshold-Based Correlation in DCT mid-band % Uses two PN sequences; one for a "0" and another for a "1" % 水印嵌入 clear all; % 保存开始时间 start_time=cputime; k=10; % 设置嵌入强度 blocksize=8; % 设置块的大小 midband=[ 0,0,0,1,1,1,1,0; % defines the mid-band frequencies of an 8x8 dct 0,0,1,1,1,1,0,0; 0,1,1,1,1,0,0,0; 1,1,1,1,0,0,0,0; 1,1,1,0,0,0,0,0; 1,1,0,0,0,0,0,0; 1,0,0,0,0,0,0,0; 0,0,0,0,0,0,0,0 ]; % 读入原始图像 file_name='_lena_std_bw.bmp'; cover_object=double(imread(file_name)); % 原始图像的行数与列数 Mc=size(cover_object,1); %原图的行数 Nc=size(cover_object,2); %原图的列数 % 确定可嵌入的最大信息量 max_message=Mc*Nc/(blocksize^2); % 读入水印图像 file_name='c.bmp'; message=double(imread(file_name)); %水印图像的行数与列数 Mm=size(message,1); %水印图像的行数 Nm=size(message,2); %水印图像的列数 figure(1) imshow(message,[]); title('水印'); % 将水印图像矩阵转换为0，1组成的向量 message=reshape(message,1,Mm*Nm); % 检查水印信息是否过大 if (length(message) > max_message) error('水印太大') end % 将message_vector置为全1向量，并将message写入 message_vector=ones(1,max_message); message_vector(1:length(message))=message; % 将cover_object写入watermarked image watermarked_image=cover_object; key=1100; % 重置随机数发生器状态为key rand('state',key); % 生成伪随机数 pn_sequence_zero=round(2*(rand(1,sum(sum(midband)))-0.5)); % 图象分块并嵌入 x=1; y=1; for (kk = 1:length(message_vector)) % 分块进行DCT变换 dct_block=dct2(cover_object(y:y+blocksize-1,x:x+blocksize-1)); % 如果message_vector==0 并且midband==1，那么嵌入 pn_sequence_zero ll=1; if (message_vector(kk)==0) for ii=1:blocksize for jj=1:blocksize if (midband(jj,ii)==1) dct_block(jj,ii)=dct_block(jj,ii)+k*pn_sequence_zero(ll); ll=ll+1; end end end end % 逆DCT变换 watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=idct2(dct_block); % 移动到下一块 if (x+blocksize) >= Nc x=1; y=y+blocksize; else x=x+blocksize; end end % 转换为uint8 并将watermarked_image_uint8写入watermarked_image_uint8.bmp watermarked_image_uint8=uint8(watermarked_image); imwrite(watermarked_image_uint8,'watermarked_image_uint8.bmp','bmp'); % 显示运行时间 elapsed_time=cputime-start_time, % 计算psnr psnr=psnr(cover_object,watermarked_image), % 显示嵌入水印图象与原始图象 figure(2) subplot(1,2,1); imshow(watermarked_image_uint8,[]) title('嵌入水印图像') subplot(1,2,2) imshow(cover_object,[]); title('原始图像');