1. High-Capacity Data Hiding in Halftone Images Using Minimal-Error Bit Searching and Least-Mean Square Filter
Author: Soo-Chang Pei and Jing-Ming Guo
Source: IEEE Transactions on Image Processing, Vol. 15, No. 6, pp , June 2006
Date: 26/10/2006
Speaker: Ming-Ni Wu

2. Outline Introduction Error Diffusion PSNR for Halftone Images
Data Hiding with Minimal-Error Bit Search (MEBS)
Standard MEBS
Modified MEBS
Self-Decoding Mode
Dot-Diffusion Self-Decoding Mode
Color Halftone Image Self-Deconding Mode
Robust Watermarking
Conclusions

3. Introduction
Error Diffusion
(EDF)
A gray level image
A halftone image

4. Introduction
to distribute the watermark into several EDF images (secret sharing)
Error Diffusion and Data Hiding
gray level images
halftone images
a bi-level watermark

5. Error diffusion (EDF)
255 80
100 95
200
150
130 72
137
160
110 63
121
143 90 54
TH=128, x=80
80<128=>x=0
Error=80-0=80
100+80*(7/16)=135
200+80*(3/16)=215
150+80*(5/16)=175
130+80*(1/16)=135
255
135 95
215
175 72
137
160
110 63
121
143 90 54
a grey level image x
7/16
3/16
5/16
1/16 x
7/48
6/48
3/48
5/48
1/48
Steinberg kernel
Jarvis kernel

6. Error diffusion (experiments)
Original error-diffused halftone images
512
512
PSNR=30.84 PSNR=27.15 PSNR=30.9

7. PSNR for Halftone ImagesQ 1
150 80
100 95
200
130 72
137
160
110 63
121
143 90 54
0.05
0.10
0.40 P
Filter W
Halftone image B
Original gray level image
0.59
0.31
0.39
0.37
0.74
0.51
0.28
0.54
0.63
0.43
0.25
0.47
0.56
0.35
0.21
0.05*1+0.1*0+0.05*1+0.1*1+0.4*1+0.1*0+0.05*0+0.1*1+0.05*0
=0.8
Normalized image X

8. PSNR for Halftone Images
-0.002
-0.001
0.006
-0.010
-0.03
-0.04
-0.004
0.011
0.033
0.042
0.022
-0.006
0.035
0.081
0.099
0.063
0.016
0.040
0.097
0.123
0.027
0.002
-0.003
0.013
0.053
0.073
0.049
0.014
-0.007
0.012
-0.005
7*7 filter

9. Standard MEBS X Y secret image 255 80 100 95 200 150 130 72 137 160
110 63
121
143 90 54
x2=80,80<128 =>x2’=0
y2=130,130>128=>y2’=1
Case 1:
x2’=1, Error=80-255=-175
y2’=1, Error= =-125
Total error
=|-175|+|-125|=300
Case 2:
x2’=0, Error=80-0=80
y2’=0, Error=130-0=130
=|80|+|130|= selected
secret bit 1
Gray code X
130
120
100 70
145 85 50 80 87 75 63 66 Y 1
secret
image

10. Standard MEBS (Experiments)
watermarked images
PSNR= PSNR=25.45
watermark
capacity:50%

11. Standard MEBS (Experiments)
watermarked images
PSNR=28.9 PSNR=26.9 PSNR=28.95
watermark
capacity:33%

12. Modified MEBS X Y secret image secret bit 1 Gray code 255 80 100 95
ERRth=128
x2=80,80<128 =>x2’= 0
y2=130,130>128=>y2’=1
Case 1:
x2’=1, Error=80-255=-175=>-128
y2’=1, Error= =-125
Total error
=|-128|+|-125|=253
Case 2:
x2’=0, Error=80-0=80
y2’=0, Error=130-0=130=>128
=|80|+|128|= selected
secret bit 1
Gray code
255 80
100 95
200
150
130 72
137
160
110 63
121
143 90 54 X
130
120
100 70
145 85 50 80 87 75 63 66 Y 1
secret
image

13. Modified MEBS
The average ERRth value in TABLE II is

14. Modified MEBS (Experiments)
watermarked images
PSNR= PSNR=26.78
watermark
capacity:50%

15. Dot-diffusion Self-Decoding Mode
Dot Diffusion and Data Hiding
gray level images
halftone images
a bi-level watermark

16. Dot-diffusion Self-Decoding Mode16
60+70*(1/7)=70
50+70*(2/7)=70
80+70*(1/7)=90
90+70*(2/7)=110
90+70*(1/7)=100 16 16 16 … … 26 19 49 39 47 78 62 63 94
255 60 70 50 80 90
255 70 90
110
100 … …
orthogonal factor=2
diagonal factor=1

17. Dot-diffusion Self-Decoding Mode (experiments)
watermarked, 480*480, PSNR=25.39
capacity=50%
watermark,240*480
Watermarked, 480*480, PSNR=28.84
capacity=33.3%
watermark,160*480

18. Color Halftone Image Self-Deconding ModeB B
Error Diffusion and Data Hiding
a color image
a color halftone image
a bi-level watermark

19. Color Halftone Image Self-Deconding Mode (experiments)
RGB
CMYK

20. Robust Watermarking
512 64 64
512 8
Each block can embed the same information bit.
We can use the majority voting to recover the damaged portion. 8

21. Robust Watermarking (experiments)
Tampering attack
92.65%

22. Robust Watermarking (experiments)
Cropping attack
10% % % %
99.54% % % %

23. Robust Watermarking (experiments)
Rotated attack
(a)10° (i)95.87%
(b)15° (j)94.12%
(c)20° (k)92.55%
(d)25° (l)91.24%
(e)30° (m)90.65%
(f)35° (n)90.14%
(f)40° (o)89.94%
(h)45° (p)89.92%

24. Conclusions
A high-capacity data-hiding method in halftone image using the MEBS technique is proposed.
The embedded halftone images are robust enough to survive under various attacks.