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A Color Image Hidden In a Grey-Level Image

Reporter ： Cheng HsuDate ： 2009/11/06

IS&T Third European Conference on Colour in Graphics, Imaging, and Vision, CGIV’2006, pp. 226–231, (Leeds, UK), June 2006.

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Outline Introduction The proposed method

Color quantization Layer running Spatial data hiding method

Results Conclusion

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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

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Color quantization

Find the K-colors K-mean clustering algorithm.

))(),((.minarg)}(,{ 2

1 1,

)(,,

,

kClIdistPkCPN

l

K

kkl

kCPkl

kl

random

index

R G B

1 12 50 200

2 250 120 56

3 33 47 54

.. … .. …

K … … …

find min(dist)

index

group

1 (9,12)(20,113)(…,..)

2 (29,156)(101,51)(……)

3 (23,143)(42,213)(……)

.. …

K …

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Layer running

Choosing the closer color from the current one.

Layer running algorithm.

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A view of the layer running in the RGB cube.

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8

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Spatial data hiding method – LSB

Get a marked pixel

60908*254*3

:,/

m

pixelofnomberNNmEf

lM bnInInI 2mod)()()(

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Results

Application of the layer running algorithm on the baboon image:

(b) Color palette after color ordering

(c) index image

(e) Recover image (d) stego-image image

(a) Original color image

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Application of the layer running algorithm on the airplane image:

(a) Original color image

(b) Color palette after color ordering

(c) index image

(d) stego-image image

(e) Recover image

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PSNR comparisions

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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