%DFT水印源碼
%參照DCT2修改，只為拋磚引玉
%快樂！
%嵌入代碼
clc
clear all;

% 保存開始時間
start_time=cputime;

k=110;                           % 設置嵌入強度系數
blocksize=8;                    % 塊的大小

filter_m=[  0,0,0,0,0,0,0,0;    % 濾波矩陣
            0,1,1,1,1,1,1,0;
            0,1,1,1,1,1,1,0;
            0,1,1,1,1,1,1,0;
            0,1,1,1,1,1,1,0;
            0,1,1,1,1,1,1,0;
            0,1,1,1,1,1,1,0;
            0,0,0,0,0,0,0,0 ];
        
% 讀入原始圖像
file_name='_lena_std_bw.bmp';
cover_object=double(imread(file_name));

% 原始圖像矩陣的行數與列數
Mc=size(cover_object,1);	        
Nc=size(cover_object,2);	       

% 最大嵌入信息量
max_message=Mc*Nc/(blocksize^2);

% 讀入水印圖像
file_name='c.bmp';
message=double(imread(file_name));
%水印圖像矩陣的行數與列數
Mm=size(message,1);	                
Nm=size(message,2);	                

message_vector=reshape(message,1,Mm*Nm);

% 檢查水印信息是否過大
if  Mm*Nm>max_message
   error('水印信息過大')
end



% 將cover_object（原圖矩陣）寫入watermarked_image
watermarked_image=cover_object;

%置隨機數發生器的狀態為1100
rand('state',1100);

% 產生偽隨機序列
pn_sequence=round(2*(rand(1,sum(sum(filter_m)))-0.5));

% 將圖像分塊
x=1;
y=1;
h=0;
h=waitbar(0,'嵌入水印，請等待');
for (kk = 1:length(message_vector))

    % 做傅立葉變換
    fft_block=fft2(cover_object(y:y+blocksize-1,x:x+blocksize-1));
    abs_block=abs(fftshift(fft_block));
    angle_block=angle(fft_block);
    % 當message_vector=0且filter_m=1時用偽隨機序列疊加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(ii,jj)=abs_block(ii,jj)+k*pn_sequence(ll);
                    ll=ll+1;
                end
            end
        end
    end
    
    % 進行傅立葉逆變換
    abs_block=fftshift(abs_block);
    watermarked_image(y:y+blocksize-1,x:x+blocksize-1)=abs(ifft2(abs_block.*exp(i*angle_block)));    
    
    % 移動到下一塊
    if (x+blocksize) >= Nc
        x=1;
        y=y+blocksize;
    else
        x=x+blocksize;
    end
    waitbar(kk/length(message_vector),h);
end
close(h);

% 轉換為uint8，并寫入
watermarked_image_int=uint8(watermarked_image);
imwrite(watermarked_image_int,'fft2_watermarked.bmp','bmp');

% 計算運行時間
elapsed_time=cputime-start_time,

% 計算psnr
psnr=psnr(cover_object,watermarked_image),

% 顯示水印，嵌入水印圖像與原始圖像
figure(1)
imshow(message,[]);
title('水印');
figure(2)
subplot(1,2,1);
imshow(watermarked_image,[])
title('嵌入水印圖像')
subplot(1,2,2);
imshow(cover_object,[]);
title('原始圖像');