基于傅立叶变换的数字水印嵌入技术

%基于傅立叶域的数字水印 %注意:水印必须为40*40的二值图像 %因为40阶的二维arnold置乱周期为30,所以嵌入时置乱8次,提取时置乱22.可以根据自己的需要更改. %嵌入源码 clc clear all; % 保存开始时间 start_time=cputime; iTimes=8; %置乱次数 k=1.1; % 设置嵌入强度系数 blocksize=8; % 块的大小 filter_m=[ 1,1,1,1,1,1,1,1; % 滤波矩阵 1,1,1,1,1,1,1,1; 1,1,0,0,0,0,1,1; 1,1,0,0,0,0,1,1; 0,0,0,0,0,0,0,0; 0,0,0,0,0,0,0,0; 0,0,0,0,0,0,0,0; 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))/255; % 原始图像矩阵的行数与列数 Mc=size(cover_object,1); Nc=size(cover_object,2); % 最大嵌入信息量 max_message=Mc*Nc/(blocksize^2); % 读入水印图像 file_name='watermark.bmp'; message=double(imread(file_name)); %水印图像矩阵的行数与列数 Mm=size(message,1); Nm=size(message,2); % 检查水印信息是否过大 if Mm*Nm>max_message error('水印信息过大') end %对水印图像进行Arnold置乱 if Mm~=Nm error('水印矩阵必须为方阵'); end if Mm~=40 error('必须为40*40大小,或者修改置乱次数'); end tempImg=message; for n=1:iTimes % 次数 for u=1:Mm for v=1:Nm temp=tempImg(u,v); ax=mod(u+v,Mm)+1; ay=mod(u+2*v,Nm)+1; outImg(ax,ay)=temp; end end tempImg=outImg; end message_vector=reshape(outImg,1,Mm*Nm); % 将cover_object（原图矩阵）写入watermarked_image watermarked_image=cover_object; %置随机数发生器的状态为1100 key=1100; rand('state',key); % 产生伪随机序列 pn_sequence_zero=round(2*(rand(1,sum(sum(filter_m)))-0.5)); pn_sequence_one=round(2*(rand(1,sum(sum(filter_m)))-0.5)); % 将图像分块 x=1; y=1; h=waitbar(0,'嵌入水印，请等待'); for (kk = 1:length(message_vector)) % 做傅立叶变换 fft_block=fft2(cover_object(y:y+blocksize-1,x:x+blocksize-1)); %计算幅值 abs_block=fftshift(abs(fft_block)); %计算相位 angle_block=angle(fft_block); % 当message_vector=0且filter_m=1时用伪随机序列pn_sequence_zero叠加abs_block % 当message_vector=1且filter_m=1时用伪随机序列pn_sequence_one叠加abs_block ll=1; if (message_vector(kk)==0) for ii=1:blocksize for jj=1:blocksize if (filter_m(ii,jj)==1) abs_block_o=abs_block(ii,jj); abs_block(ii,jj)=abs_block(ii,jj)*(1+k*pn_sequence_zero(ll)); abs_block(blocksize-ii+1,blocksize-jj+1)=abs_block(blocksize-ii+1,blocksize-jj+1)+abs_block(ii,jj)-abs_block_o; ll=ll+1; end end end else for ii=1:blocksize for jj=1:blocksize if (filter_m(ii,jj)==1) abs_block_o=abs_block(ii,jj); abs_block(ii,jj)=abs_block(ii,jj)*(1+k*pn_sequence_one(ll)); abs_block(blocksize-ii+1,blocksize-jj+1)=abs_block(blocksize-ii+1,blocksize-jj+1)+abs_block(ii,jj)-abs_block_o; ll=ll+1; end end end end % 进行傅立叶逆变换 abs_block=fftshift(abs_block); watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=abs(ifft2(abs_block.*exp(i*angle_block))); % 移动到下一块 if (x+blocksize) >= Nc x=1; y=y+blocksize; else x=x+blocksize; end waitbar(kk/length(message_vector),h); end close(h); % 转换为uint8，并写入 watermarked_image_int=uint8(watermarked_image*255); imwrite(watermarked_image_int,'dft2_watermarked.bmp','bmp'); % 计算运行时间 elapsed_time=cputime-start_time, % 计算psnr PSNR=psnr(cover_object,watermarked_image), % 显示水印，嵌入水印图像与原始图像 figure(1) subplot(1,2,1) imshow(message,[]); title('原始水印'); subplot(1,2,2); imshow(tempImg,[]); title('置乱水印'); figure(2) subplot(1,2,1) imshow(watermarked_image,[]); name='嵌入水印图像'; title(strcat(num2str(name),' k=',num2str(k),' PSNR=',num2str(PSNR))); subplot(1,2,2) imshow(cover_object,[]) title('原始图像');