1. 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 2012/05/31

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

3. 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. 4 Extract the K-colors K-means Proposed scheme random indexRGB 11250200 225012056 3334754..… … K……… find min(dist) indexgroup 1(1,5)(23,100)(…,..) 2(20,106)(100,20)(……) 3(35,250)(37,200)(……)..… K…

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

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

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

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

9. 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

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

11. 11 Experimental Results PSNR comparision

12. 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

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