1. A Color Image Hidden in a
Grey-Level Image
IS&T Third European Conference on Colour in Graphics, Imaging, and Vision, CGIV’2006, pp. 226–231, (Leeds, UK), June 2006.
Author : M. Chaumont and W. Puech
Adviser :Jiin -Chiou Cheng
Reporter :Wei-De Hsu

2. Outlines Introductions Proposed method Experimental Results
Color quantization
Layer running
Spatial data hiding method
Experimental Results
Conclusions

3. Introductions
A grey-level image is freely accessible but only secret key owners may rebuild the color image.
Our aim is thus to protect the color information by embedding this information in the grey level image.
The proposed method is made of three major steps
Color quantization
Ordering
Data hiding

4. Proposed scheme Extract the K-colors K-means find min(dist) random
index R G B 1 12 50
200 2
250
120 56 3 33 47 54 .. … K
index
group 1
(1,5)(23,100)(…,..) 2
(20,106)(100,20)(……) 3
(35,250)(37,200)(……) .. … K
find min(dist)
random

5. Proposed scheme Layer running
Choosing the closer color from the current one.
Gray_value=1
Gray_value=2 5

6. Spatial data hiding method – LSB
Proposed scheme
Spatial data hiding method – LSB
get a marked pixel IM(n) 6

7. Experimental Results
images of size:256×256pixels 7

8. Experimental Results (a) Quantified image (b) Color palette of
the quantified image
(c) Indexed image from the
quantified image 8

9. Experimental Results
Application of the layer running algorithm on the baboon image:
(a) Color palette after
color ordering
(b) index image
(c) stego-image image
(d) Recover image 9

10. Experimental Results
Application of the layer running algorithm on the airplane image:
(a) Color palette after
color ordering
(b) index image
(c) stego-image image
(d) Recover image

11. Experimental Results
PSNR comparision 11

12. Conclusions
Proposed a method to hide the color information in a grey-level image
three major steps
color quantization
the color ordering
the data hiding
The results obtained show good performances