VQ-Based Digital Image Watermarking Method
Author:Zhe-ming Lu, Jeng-shyang Pan and Sheng-he Sun
Source:IEEE ELECTRONICS LETTERS, VOL. 36, NO. 14,
JULY 2000, pp. 1201-1202.
Adviser :Dr. Chang, Chin-Chen
Reporter :Liang, Min-Chen
Date :2003/05/27
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Outline
INTRODUCTION
PROPOSED METHOD
EXPERIMENTAL RESULTS
CONCLUSIONS
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INTRODUCTION
Digital Watermarking
Visible Invisible
Spatial Domain Frequency Domain
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Framework of Invisible Watermark
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PROPOSED METHOD
Watermark W (gray scale, 64 × 64)
Original image "Lena“ (gray scale, 512 × 512) To be embedded 32768 bits
Block size=4 x 4 Divided into 16384 blocks 64x64x8=32768
(512x512)/(4x4)=16384 32768/16384=2bits/block
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Embedding Watermark
BC codewords EC codewords UC codewords
0 0 0
1 1 1
2 2 2
. .
scrambled .
.
.
+ .
.
.
.
. . .
. . .
253 765 1021
254 766 1022
255 767 1023
Size of the basic codebook : 256 (is generated by the LBG algorithm)
Size of the extended codebook : 256 x (4-1) (are randomly produced in BC’s neighbouring region)
Size of the user codebook : 256 x 4 (BC scrambled EC = UC)
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Embedding Watermark (cont.)
X:BC codewords o:EC codewords D(X,o)<120
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Embedding Watermark (cont.)
Two bits of Watermark Integer g Index Ex.
00 0 BCi BC0
01 1 ECj+1-g EC0
10 2 ECj+1-g EC1
11 3 ECj+1-g EC2
j=ix3
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Embedding Watermark (cont.)
00 10 11 01 watermark UC codewords
0
1
BC251 BC98 BC3 BC25 2
index table EC295
.
BC251 45
.
EC11 501
BC251 EC295 EC11 EC75 .
EC75 1021
1022
1023
UC45 UC2 UC501 UC1021
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Extracting Watermark
Each watermarked image block Set g = Two bits of the watermark
Find the nearest codeword in 0 00
the basic codebook
Find the nearest codeword in
ECj mod 3 +1
the extended codebook
Ex. EC3 1 01
EC4 2 10
EC5 3 11
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Extracting Watermark (cont.)
00 10 11 01 watermark UC codewords
0
1
BC251 BC98 BC3 BC25 2
index table EC295
.
BC251 45
.
EC11 501
BC251 EC295 EC11 EC75 .
EC75 1021
1022
1023
UC45 UC2 UC501 UC1021
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EXPERIMENTAL RESULTS
VQ compressed Lena image Watermarked Lena image
(PSNR=30.78d b) (PSNR=30.59 d b)
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CONCLUSIONS
A digital image watermarking technique
based on VQ has been presented.
It is efficient and has a high level of
secrecy.
The watermarked image withstands VQ
compression and the extraction process does
not require the original image.
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