1. An image-hiding method with high hiding capacity based on best-block matching and k-means clustering
Source: Pattern Recognition, Volume 40, Issue 2, February 2007, pp
Authors: Ran-Zan Wang and Yao-De Tsai
Speaker: Yi-Pei Hsieh
Date: 　　　　

2. Introduction cover image extracted secret image stego image
Goals
● High hiding capacity
● Stego-image with high quality
Techniques
● Extracted secret image with Acceptable quality
● best-block matching
● k-means clustering
2019/7/31

3. The proposed scheme (1/6)
Candidate blocks generation
k-means clustering
Embedding
cover image
Candidate blocks 1 .
N-2
N-1
(43, 57, …, 40)
Candidate blocks 1 .
N-2
N-1
k representative blocks 1 .
k-2
k-1
q LSBs
Best-block matching
Not well-matched
blocks
secret image
Candidate blocks 1 .
N-2
N-1
(43, 57, …, 40) No
Find nearest block
MSE ≤ thd
Index table
Yes
2019/7/31

4. The proposed scheme (2/6)
Candidate blocks generation
Cover image (64 × 64)
Candidate blocks
q LSBs (q=3) 1 2
1023
1022
( 9,10,18,17) 8 16 12 14 22 18 8 16
(20,25,17,11)
(24,45,47,76)
Block
(78,22,77,20)
Clean and reconstruct q LSBs of cover image (q=3)
(33,32,97,98)
(20,55,53,26) 9 10 18 17
2019/7/31
Block

5. The proposed scheme (3/6)
Best block matching
Candidate blocks
Index table
Secret image (64 × 64) 1 2
1023
1022
( 9,10,18,17) 1 1 … 12 34 3 22 45 67 5 7
(24,45,47,76)
(24,45,47,76) 1
Yes
(20,25,17,11) 21 44 75 78
thd = 10
(21,44,45,78)
(78,22,77,20) 1 No
Not well-matched
blocks
(33,32,97,98)
(20,55,53,26) 1
flag
2019/7/31

6. The proposed scheme (4/6)
k-means clustering
Candidate blocks
( 9,10,18,17) 1 2
1023
1022
(35,22,45,78)
(24,45,47,76)
The k representative blocks 1
(20,25,17,11)
(14, 8,19,23)
(35,22,45,78)
(14, 8,19,23) 1
Not well-matched
blocks
K-means clustering
(78,22,77,20) 1
(33,32,97,98)
k-2
(72,26,38,41)
(20,55,53,26) 1
k-1
(20,55,53,26)
flag
Index table 2 1 … 12 34 3 22 45 67 5 7
2019/7/31

7. The proposed scheme (5/6)
Embedding
The k representative blocks
Huffman output stream Huffman table Parameters (Hs, Ws, b, t, k, thd)
The index table
Huffman coding
Flag
q LSBs of cover image
2019/7/31

8. The proposed scheme (6/6)
Extraction
The k representative blocks
q LSBs of stego image
The index table
Huffman de-coding
Huffman output stream Huffman table Parameters (Hs, Ws, b, t, k, thd)
Flag
Candidate blocks
Extracted secret image
( 9,10,18,17)
(35,22,45,78)
(24,45,47,76) 1
1022
(33,32,97,98)
2019/7/31
1023
(20,55,53,26)

9. Experimental results (1/3)
512×512 test images
2019/7/31

10. Experimental results (2/3)
512 × 512 test images
Block size: 4 × 4 ; q LSBs = 2
Each index occupies t =14 bits
thd=70, k=2175
Extracted secret image
Stego-image
Cover
Embedded
Baboon
Tiff
Scene
Lena
Jet
Pepper
43.95/ 36.06
44.05/36.61
44.16/ 35.73
44.18/ 34.84
44.19/ 34.68
44.19/ 27.73
44.04/ 31.78
44.08/ 35.02
44.16/ 36.21
44.27/ 33.93
44.19/ 27.91
43.97/ 37.39
44.04/ 34.72
44.13/ 36.70
44.24/ 34.60
44.21/ 28.07
43.76/ 35.45
44.10/ 32.33
44.14/ 38.13
44.12/ 36.32
44.20/ 27.99
43.81/ 35.85
44.11/ 32.15
44.15/36.52
44.15/ 35.31
44.23/28.03
43.79/ 35.38
44.14/32.38
44.17/ 37.01
44.09/ 37.43
Mean
44.20/27.95
43.85/36.02
44.09/ 32.05
44.12/ 35.80
44.14/ 36.66
44.19/ 34.97
2019/7/31

11. Experimental results (3/3)
Block size: 4 × 8 ; q LSBs = 3
Each index occupies t = 13 bits
k=1375
secret image (1024 ×1024)
extracted secret image (512 × 512) PSNR=29.63
cover image (512 × 512)
stego image (512 × 512)
PSNR=37.79
2019/7/31

12. Conclusions An image-hiding method is proposed
Applying Best-block matching and k-means clustering
Achieving high hiding capacity, the stego-image with high quality, and the extracted secret image with acceptable quality
2019/7/31

13. Thanks for your listening...

15. Replace the old vectors
k-means clustering
Index sets
Not well-matched
blocks 1 .
k-2
k-1
(1, 2, 5, 9, 45, …)
(101, 179, 201, …) 1 .
m-1
(8, 27, 38, 19, 200, …)
(23, 0, 67, 198, 224, …) 1 .
k-2
k-1
Compute mean values
Replace the old vectors
2019/7/31

16. Huffman coding compress Output: 000 001 010 011 100 101 11 11 c o m p2 1 c
000 o
001 m
010 p
011 r
100 e
101 s 11
4/8
2/8
2/8
2/8
1/8 c
1/8 o
1/8 m
1/8 p
1/8 r
1/8 e
2/8 s
Output:
2019/7/31