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imshow() black image

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Mostfa Abd El-Aziz
Mostfa Abd El-Aziz 2020-8-26
编辑： Mostfa Abd El-Aziz 2020-8-26
%%%%% Complete Code %%%%%%%%%%%
clc
close all
clear
%% Input images
I=imread('gl1.jpg');
I=imresize(I,[512,512]);
logo=imread('watermark.jpg');
logo=imresize(logo,[64,64]);
figure
subplot(1,4,1)
imshow(I)
title('Host Image')
subplot(1,4,2)
B=I(:,:,3); % Blue Channel
imshow(logo)
xlabel('Logo (Watermark Image)')
gf=100; % Watermark Strength
n_dct=60; % <=64
zigzag=[1 9 2 3 10 17 25 18 11 4 5 12 19 26 33 41 34 27 20 13 6 7 14 21 28 35 42 49 57 ...
50 43 36 29 22 15 8 16 23 30 37 44 51 58 59 52 45 38 31 24 32 39 46 53 60 61 54 47 40 48 55 62 63 56 64];
dct_idx=zigzag(1:n_dct);
%% key generation:
key=randperm(512*512,64*64);
%% Block Selection (Embedding Step):
c=0;
Watermarked_B=B;
for i=1:64:64*64-63
c=c+1;
block_index=key(i:i+63);
blockB=double(reshape(B(block_index),[8,8]));
% discrete cosine transform:
dct_blockB=dct2(blockB);
% Singular Value Decomposition:
[U,S,V]=svd(dct_blockB(dct_idx));
sigmaB=S(1); % Biggest Singular Value
% embedding watermark image:
if logo(c)==1
S(1)=sigmaB+gf;
else
S(1)=sigmaB-gf;
end
reference{i}=S;
coeffs=U*S*V; % inverse svd
rec_dct_block=zeros(8);
rec_dct_block(dct_idx)=coeffs;
rec_block=idct2(rec_dct_block); % inverse dct
row_block=reshape(rec_block,1,64);
Watermarked_B(block_index)=row_block;
end
Watermarked_image=I;
Watermarked_image(:,:,3)=Watermarked_B;
subplot(1,4,3),
imshow(Watermarked_image);
title('Watermarked Image')
%% Extraction Step
Ex_watermark=zeros(8);
Watermarked_B=Watermarked_image(:,:,3);
c=0;
for i=1:64:64*64-63
c=c+1;
block_index=key(i:i+63);
blockB=double(reshape(B(block_index),[8,8]));
% discrete cosine transform:
dct_blockB=dct2(blockB);
% Singular Value Decomposition:
[Ub,Sb,Vb]=svd(dct_blockB(dct_idx));
Sbw=reference{i};
sigmaB=Sb(1); % Biggest Singular Value - Host
sigmaBW=Sbw(1); % Biggest Singular Value - Watermarked
% Extracting watermark image:
if sigmaBW>sigmaB
Ex_watermark(c)=1;
end
end
subplot(1,4,4),
imshow(double(Ex_watermark))
xlabel('Extracted Watermark');
  2 个评论
KSSV
KSSV 2020-8-26
Try:
imshow((Ex_watermark))
Mostfa Abd El-Aziz
Mostfa Abd El-Aziz 2020-8-26
Dear,KSSV i use your recommended suggested code bit the problem still not solved

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回答（1 个）

Ezgi Aslan
Ezgi Aslan 2020-8-26
if sigmaBW>sigmaB
Ex_watermark(c)=1;
end
this code doesn't run so Ex_watermark always include zeros (8x8). And shows black image
  4 个评论
显示 2更早的评论
Image Analyst
Image Analyst 2020-8-26
Mostfa, please attach gl1.jpg and watermark.jpg if you need more help.
I'm attaching my own watermarking demo, for what its worth.
Mostfa Abd El-Aziz
Mostfa Abd El-Aziz 2020-8-26
编辑：Mostfa Abd El-Aziz 2020-8-26
Dear , Image Analysy This is my attached images

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