Cryptography Reference
In-Depth Information
i
2
0000 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111
j
0
j
1
0000
j
2
j
3
j
4
0001
j
5
j
6
j
7
0010
j
8
j
9
j
10
0011
j
11
j
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0100
j
14
j
15
j
16
0101
j
17
j
18
j
19
0110
j
20
j
21
j
22
0111
i
1
j
23
j
24
j
25
1000
j
26
j
27
j
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1001
j
29
j
30
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31
1010
j
32
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1011
j
35
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36
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37
1100
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38
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39
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40
1101
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41
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42
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43
1110
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44
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45
1111
Fig. 12.7.
An example of the combination of MDC and watermarking, an extension
to Fig. 12.3(b).
12.6 An Example for Watermarking with MDC
Fig. 12.7 is the example that follows Fig. 12.3(b). Here the codebook size
is L = 8, and each codeword is 3-bit in length. Consequently, when using
the watermarking scheme in Eq. (12.7), Fig. 12.7 is a direct extension of
Fig. 12.3(b). This is because each watermarked codeword is 4-bit in length.
The codebook with length 2
4
=2L = 16 is trained in advance to deal with
watermark embedding. From another perspective, for watermarking purposes,
the effective length of the codebook for reconstructing the compressed image
is halved. The watermarked image quality with MDC is somewhat degraded.
The original image X employed has size 512512. The two watermarks,
W
1
and W
2
, both have sizes 128128. In VQ encoding, the original image is
divided into 44blocksX
k
, and each block is represented by one codeword
