halftone image data hiding with block-overlapping parity check
TRANSCRIPT
Richard Y. M. Li, Oscar C. Au, Carman K. M. Yuk,Shu-Kei Yip , Sui-Yuk Lam
Department of Electronic and Computer Engineering
The Hong Kong University of Science and Technology
Reporter: Liu Rui2008.5.6
OutlineIntroductionThe Proposed BOPC AlgorithmExperimental ResultsConclusion
Introduction Hiding information into the digital mediaA new data hiding algorithm for halftone
images named Block-Overlapping Parity Check(BOPC)
Based on Data Hiding Smart Pair Toggling(DHSPT)
Reduce the number of pair toggling required in DHSPT
Data Hiding Smart Pair Toggling(DHSPT)A pseudo-random number generator with a
seed is used to identify the pseudo-random location where the data is embedded.
The pixel at the location is 0 or 1 according to the data bit to be embedded.
Master pixel：A pixel at a pseudo-random location needs to
self-toggleThere are M pixels of opposite color in the neighborhood.
Slave pixel：One of the M pixels is chosen to self-toggle
also. 1 0
0
0 1 1
1
0 1
1 1
0
0 0 1
1
0 1
Data Hiding Smart Pair Toggling(DHSPT)
8
10 ),()(),(
iixxfiwnmcon
),( yxfyx
yx
,0
,1
Where w(i) = 1 for i = 1, 3, 6, 8 and w(i) = 2 for i = 2, 4, 5, 7
X1
X 2 X3
X4 X0 X5
X6 X7 X8
Block-Overlapping Parity Check(BOPC)Master mapParity mapToggle map
……………………1…………………………0………………………………………………………………………………1………………………1……………………0……………………………………………………………………1……………………
M S
1,1 121,133
1,2 193,34
…… ……
2,1 34,351
2,2 543,68
…… ……
1
0 1 … …
0 1
1
1
0 1 0 1
0 1 1
0 1
1 0 0 1 0
1 1 1 1 0
0 1 0 0 1Master Map
Location Mapping Table
Host Image
Master map
A pseudo-random number generator is used to generate a set of (2Lx+1)*(2Ly+1) pseudo-random
Parity map
1 0 1 0 1
0 1 1
0 1
1 0 0 1 0
1 1 1 1 0
0 1 0 0 1
1
P11=(M11+M12+M13+M21+M22+ M23+M31+M32+M33)mod 2 =(1+0+1+0+1+1+1+0+0)mod 2 =1
P12=(M13+M14+M15+M23+M24+ M25+M33+M34+M35)mod 2 =(1+0+1+1+0+1+0+1+0)mod 2 =1
1 1 1 1
1 1
Master Map Parity Map
Parity map
Toggle map
If Pij and Lij happen to be the same,Tij will be zero and no toggling is need.
Tij=Pij⊕Lij
0 1 1 0
1 1
0 1 0 0 0 1
1 1 0 1 0 0
1 1 0 1 0 1
0 1 0 0 1 1
0 1 0 0 1 0
1
0
0
1
1
0
0
1
0
1
0
1
0
0
1
0
1
0
0
1
0
0
0
1
0
1
1
1
0
1
1
0
1
1
0
1
1 1 1 1 0 1
0 0 0 1 0 0
1 1 1 1 1 0
1 0 0 1 0 0
0 0 1 1 1 0
1 1 1 1 1 1
Toggle map
L
P
⊕
Toggle Map
Bubble Formation
1
0
0
1
1
0
0
1
0
1
0
1
0
0
1
0
1
0
0
1
0
0
0
1
0
1
1
1
0
1
1
0
1
1
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
0
1
0
1
0
0
1
0
0
0
1
0
1
1
1
0
1
1
0
1
1
0
1
4 4
4 4 2
33
2
2
2
1
0
0
3
3
0
0
1
0
1
0
1
0
0
1
0
1
0
0
2
0
0
0
2
0
2
4
4
0
2
1
0
4
4
0
1
Bubble Formation
Watermark Insertion
Example
1 1
1 0
1
0 1 0 1
0 1 1
0 1
1 0 0 1 0
1 1 1 1 0
0 1 0 0 1
M
P
0 0
1 1L
⊕ 1 1
0 1
T
3 3
0 1T’
1
0 1 0 1
0 1 1
0 1
1 0 0 1 0
1 1 1 1 0
0 1 0 0 1
0
0
0 0
1 1P’
M’
Experimental Results
ConclusionCan hide a large amount of data in halftone
images.Comparing with DHSPT,BOPC can reduce
half of the pair toggling required.Has a high MPSNR and good visual quality as
shown in the experimental results.