1. A Semi-blind Watermarking Based on Discrete Wavelet Transform
Authors: Chin-Chen Chang, Yung-Chen Chou,
and Tzu-Chuen Lu
Speaker: Yung-Chen Chou
Date: Dec. 12, 2007

2. Introduction
Invisible
Visible
Yung-Chen Chou

3. Introduction (Cont.) Framework of invisible watermark
Embedding algorithm
Yung-Chen Chou
Detecting algorithm

4. Haar Wavelet Transform
Introduction (Cont.)
Haar Wavelet Transform
Phase 1) Horizontal :
L H a b c d e f g h i j k l m n o p A B C D E F G H I J K L M N O P
A+B
C+D
A-B
C-D
E+F
G+H
E-F
G-H
I+J
K+L
I-J
K-L
M+N
O+P
M-N
O-P
Phase 2) Vertical : HH HL LH LL a b c d e f g h i j k l m n o p L H
a+e
b+f
c+g
d+h
i+m
j+n
k+o
l+p
a-e
b-f
c-g
d-h
i-m
j-n
k-o
l-p
Yung-Chen Chou

5. The Proposed Method Image X X’ X* Watermark W W’ W* Codebook training
Permute
DWT
Codebook
Image X X’ X*
Encode
coefficients
Index
table
Permute
DWT
Watermark W W’ W*
Yung-Chen Chou
Trusted Authenticated Center

6. The Proposed Method (Cont.)
71, 114, 97, 101
114, 115, 101, 124 71
114
115
180 97
101
124 86 53
128
119
116
146
127
129
115, 180, 124, 86
97, 101, 53, 128
101, 124, 128, 119
124, 86, 119, 116
53, 128, 146, 127 X*
Normalized LL2
coefficients of X*
128, 119, 127, 129
119, 116, 129, 86
Training pool
Codebook training (LBG)
96, 108, 109, 106
53, 128, 146, 127
115, 180, 124, 86
97, 101, 53, 128
Trained codebook 1 2 3
Yung-Chen Chou

7. The Proposed Method (Cont.)31
198
186
124
146
211
140
104
119
126
180
100
156 86 1 2 3
96, 108, 109, 106
53, 128, 146, 127
115, 180, 124, 86
97, 101, 53, 128
Trained codebook
Normalized LL2
coefficients of W* W* 2 1
Index table
Yung-Chen Chou

8. The Proposed Method (Cont.)
Watermark extracting
Codebook
training
Permute
DWT
Codebook
Image V V’ V* 2 1
Index table
DWT
IDWT
Permute
Trusted Authenticated Center W’ W*
W**
Yung-Chen Chou
Watermark We

9. Experimental Results Yung-Chen Chou
Table 2. The visual quality of the extracted watermark by using the proposed method (size of sliding window =22)
Watermarks
Host images
Baboon
Barbara
Goldhill
Lena
Sailboat
Zelda -
31.594
31.581
29.791
28.319
26.696
Yung-Chen Chou

10. Experimental Results (Cont.)

11. Experimental Results (Cont.)

12. Conclusions
The proposed method provides a greater control in terms of the robustness of the watermark.
Yung-Chen Chou