1. Image camouflage by reversible image transformation
Source: Journal of Visual Communication and Image Representation,
Vol. 40, pp , October 2016.
Authors: Dongdong Hou, Weiming Zhang, Nenghai Yu
Speaker: Jia-Long Lin
Date: 2017/06/01

2. Outline Introduction Related Work Proposed Scheme Experimental Results
- Reversible transformation
- Tiles matching
Experimental Results
Conclusions

3. Introduction
Secret image
Camouflage image

4. Related Work σ= 1 𝑛 𝑖=1 𝑛 𝑝 𝑖 −𝑢 2 128 110 96 141 132 137 152 148 135
σ= 1 𝑛 𝑖=1 𝑛 𝑝 𝑖 −𝑢 2
128
110 96
141
132
137
152
148
135 76 84 85 74 66 73 56 62 64 70 63 61 74 71 73 79 78 72
Secret block
Target block
Camouflage block
𝑢=131
σ=218
𝑢′=71
σ′=87
𝑝 𝑖 ′′ =𝑞 𝑝 𝑖 −𝑢 + 𝑢 ′ ⇒ − =70
𝑝 𝑖 =1/𝑞 𝑝 𝑖 ′′ − 𝑢 ′ +𝑢
Y.-L. Lee, W.-H. Tsai
A new secure image transmission technique via secret-fragment-visible mosaic images by nearly reversible color transformations
IEEE Trans. Circ. Syst. Video Technol., 24 (4) (2014), pp. 695–703

5. Related Work accessorial information:𝑞,𝑢,𝑢′
In the present paper, the authors improved Lee et al.’s method in two aspects:
Modify the transformation formula to be reversible
Reduce the information for recording tile indexes
Improve the quality of camouflage image by setting the smaller tile size

6. Proposed Scheme - Reversible transformation
128
110 96
141
132
137
152
148
135 76 84 85 74 66 73 56 62 64 68 50 36 81 72 77 92 88 75
Secret block
Target block
Camouflage block
𝑢=131
𝑢′=71
∆𝑢=𝑟𝑜𝑢𝑛𝑑 𝑢 ′ −𝑢 =−60
𝑝 𝑖 ′′ = 𝑝 𝑖 +∆𝑢=128−60=68

7. Proposed Scheme - Reversible transformation
130
100 70
250
255
225
195
Secret block
Target block
Camouflage block
𝑢=100
𝑢′=250
𝑇=30
Δ𝑢 Δ𝑢+255− 𝑂 𝑚𝑎𝑥 , 𝑖𝑓 𝑂 𝑚𝑎𝑥 −255 <𝑇 Δ𝑢−𝑇, 𝑖𝑓 𝑂 𝑚𝑎𝑥 −255 ≥𝑇
Δ𝑢=150⇒Δ𝑢=125

8. Proposed Scheme - Reversible transformation70
200
230
250
100
130
160
180
Secret block
Target block
Camouflage block
𝑢=200
𝑢′=100
𝑇=30
Δ𝑢 Δ𝑢+ 𝑈 𝑚𝑖𝑛 , 𝑖𝑓 𝑈 𝑚𝑖𝑛 <𝑇 Δ𝑢+𝑇, 𝑖𝑓 𝑈 𝑚𝑖𝑛 ≥𝑇
Δ𝑢=−100⇒Δ𝑢=−70

9. Proposed Scheme - Reversible transformation
𝑟 𝑖 𝑝 𝑖 ′′ −255, 𝑖𝑓 𝑝 𝑖 ′′ ≥255 0− 𝑝 𝑖 ′′ , 𝑖𝑓 𝑝 𝑖 ′′ ≤0
Δ𝑢 8×𝑟𝑜𝑢𝑛𝑑 Δ𝑢 8 , 𝑖𝑓Δ𝑢>0 8×𝑟𝑜𝑢𝑛𝑑 Δ𝑢 8 +4, 𝑖𝑓Δ𝑢<0
Δ 𝑢 ′ = Δ𝑢 4
accessorial information:Δ 𝑢 ′ ,rotation directions,𝑅

10. Proposed Scheme - Tiles matching10 2 1 3 4 8 5 6 9 3 1 2
𝑘=3
𝑐𝑙𝑎𝑠𝑠 1, 𝑖𝑓 𝑆𝐷[0,3] 2, 𝑖𝑓 𝑆𝐷[4,6] 3, 𝑖𝑓 𝑆𝐷>6
Secret image (SD) 2 8 3 1 5 6 4 9 1 3 2 1 3 2 1 3 2
SD= 1 𝑛 𝑖=1 𝑛 𝑝 𝑖 −𝑢 2
Target image (SD)

11. Proposed Scheme - Tiles matching

12. Experimental Results
(a) Secret image. (b) Target image. (c) Camouflage image created from (a) and (b).
(d) Recovered secret image using right key. (e) Recovered secret image using a wrong key.

13. Experimental Results
Fig. 1 (a) Secret image. (b) Target image. (c) Camouflage image by setting 3×3 block. (d) 4×4 block. (e) 6×6 block. (f) 8×8 block. (g) 12×12 block. (h) 16×16 block.

14. Experimental Results
The results by setting the different block size of Fig. 1.
Block size
Transformed image (RMSE)
Camouflage image (RMSE)
MAI (bpp)
3×3
13.35
39.09
1.19
4×4
16.67
21.76
0.7013
6×6
21.18
22.92
0.3501
8×8
24.39
24.75
0.2331
12×12
29.14
29.29
0.1580
16×16
32.28
32.36
0.1358
minimum root mean square error (RMSE)
the amount of the accessorial information (MAI)
𝑅𝑀𝑆𝐸= 𝑖=1 𝑛 𝑌 𝑖 ′ − 𝑌 𝑖 n
Transformed image (Before embedding accessorial information.)

15. Experimental Results
Fig. 2 (a) Secret image. (b) Target image. (c) Camouflage image created by Lee et al.’s method. (d) Camouflage image created by the proposed method.

16. Experimental Results The similarity comparison of Fig. 2.
Camouflage image
RMSE
SSIM
Fig. 2(c)
28.85
0.4567
Fig. 2(d)
21.22
0.6093
The average results on 100 pairs of test images.
Method
RMSE of transformed image
RMSE of camouflage image
MAI
Proposed method
13.29
16.03
0.6133
Lee et al.’s method
19.23
22.16
0.5309
mean structural similarity (SSIM)
𝑆𝑆𝐼𝑀 𝑥,𝑦 = (2 𝑢 𝑥 𝑢 𝑦 + 𝑐 1 )(2 σ 𝑥𝑦 + 𝑐 2 ) ( 𝑢 𝑥 2 + 𝑢 𝑦 2 + 𝑐 1 )( σ 𝑥 2 + σ 𝑦 2 + 𝑐 2 )

17. Conclusions Reversible transformation Less extra information
High image quality