1. Semi-fragile image watermarking method based on index constrained vector quantisation
Zhe-Ming Lu, Chun-He Liu, Dian-Guo Xu, Sheng-He Sun,
IEE Electronics Letters , Volume: 39 Issue: 1 , Jan. 2003
Page(s):
Advisor ：Dr. Chang, Chin-Chen
Reporter ：Jian, Yong-Xin
Date ：2003/6/10

2. Outline
INTRODUCTION
PROPOSED METHOD
EXPERIMENTAL RESULTS
CONCLUSIONS

3. INTRODUCTION
robust
Semi-fragile
fragile VQ
DCT
DWT

4. PROPOSED METHOD Original image "Lena“ (gray scale, 512 × 512)
Block size=4 x 4 Divided into blocks
(512x512)/(4x4)=16384
Watermark W (binary scale, 32 × 32)
To be embedded 1024 bits

5. PROPOSED METHOD (cont.)
Watermarking position & bits
input
vectors
index constrained VQ encoder
division
encoded indices
watermarked
output
vectors
normal VQ decoder
composition
image
EMBEDDING WATERMARK

6. PROPOSED METHOD (cont.)
Step1.Use LBG to generate a codebook.
Step2.Divide image and find its best codeword.
codebook
index 1 2 .
225
4093
4094
4095
225
original image

7. PROPOSED METHOD (cont.)
Step3.Embed bits by order.
Step4.Replicate 16 times.
225: 1
12bit/index
225
Step5.Save the position information
watermark

8. EXTRACTION WATERMARK input vectors normal VQ encoder division
encoded indices
watermarking position
extracted
watermark
extracted
bits
composition
check bit
EXTRACTION WATERMARK

9. EXPERIMENTAL RESULTS Original Lena image Watermarked Lena image
PSNR=31.85 db

10. EXPERIMENTAL RESULTS (cont.)
Original watermark
No attack, NC=1.0
JPEG, QF=100%, NC=0.9926
JPEG, QF=80%, NC=0.8053
VQ1, N=4096, NC=1.0
f. VQ2, N=8192, NC=0.8367
g. Image cropping, NC=0.9009
h. Median filtering, NC=0.0640
i. Blurring, NC=0.1233
j. Rotation, NC=0.0556

11. CONCLUSIONS
A semi-fragile digital image watermarking method is presented based on index constrained VQ.
The method is simple and efficient.
The proposed algorithm can be applied to the case of multiple watermarking by select more watermarking positions.