Blind image data hiding based on self reference
Source : Pattern Recognition Letters,
Vol. 25, Aug. 2004, pp. 1681-1689
Authors: Yulin Wang and Alan Pearmain
Speaker: Nan-I Wu (吳男益 )
Date: 2004/11/25(四 )
Introduction• Blind watermark technique: recover the
watermark without using original host data.
• The proposed method base on relative modulation of the pixel value/DCT coefficient value by referring to its estimated one.
• One is based on the estimation of pixel luminance in spatial domain
• Another based on the estimation of block DCT AC coefficients.
The proposed scheme 1 (Spatial Domain)
• For a nature image, the luminance value of one pixel normally has a relation with its neighbor.
100 100 100
100 95 100
100 100 100
LReal
The mean luminance value: Lmean
The embedding algorithm
• Embed an one-bit watermark into 3 x 3 sub-block
• Embedded bit is ‘1’
LReal ≥ Lmean + ∆1
• Embedded bit is ‘0’
LReal < Lmean - ∆2
As experienced values, ∆1 and ∆2 are selected as 5-10% of
LReal
The extracting algorithm
If LReal ≥ Lmean
extract bit ‘1’
If LReal < Lmean
extract bit ‘0’
The proposed scheme 2(Frequency Domain)
RGB to Y Cb Cr
Y = 0.299 R+ 0.587 G+ 0.114 B
R=100 G=80 B=120
90.54 = 0.299*100+ 0.587*80+ 0.114*120
DCT
The proposed scheme 2(Frequency Domain)
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(0,1)=1.13884 x (DC4-DC6)/8
Select every nine 8 x 8
blocks as one group,
in which 5 watermark bits
can be embedded
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(0,1)=1.13884 x (DC4-DC6)/8
Set ACi ≥ AC’i + ∆ to embed bit ‘1’
Set ACi ≤ AC’i - ∆ to embed bit ‘0’
∆ can be chosen as 5-15% of
the original ACi value
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(1,0)=1.13884 x (DC2-DC8)/8
Set ACi ≥ AC’i + ∆ to embed bit ‘1’
Set ACi ≤ AC’i - ∆ to embed bit ‘0’
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(0,2)=0.27881 x (DC4+DC6 – 2 x DC5)/8
Set ACi ≥ AC’i + ∆ to embed bit ‘1’
Set ACi ≤ AC’i - ∆ to embed bit ‘0’
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(2,0)=0.27881 x (DC2+DC8 – 2 x DC5)/8
Set ACi ≥ AC’i + ∆ to embed bit ‘1’
Set ACi ≤ AC’i - ∆ to embed bit ‘0’
The embedding algorithm
Block1
DC1
Block2
DC2
Block3
DC3
Block4
DC4
Block5
DC5
Block6
DC6
Block7
DC7
Block8
DC8
Block9
DC9
0 1 2
0
1 2
AC(1,1)=0.16213 x (DC1+DC9 – DC3 - DC7)/8
Set ACi ≥ AC’i + ∆ to embed bit ‘1’
Set ACi ≤ AC’i - ∆ to embed bit ‘0’
The extracting algorithm
• The original image is not require for the watermark bit detection, only the comparison of the relative value between ACi and its estimated value AC’i is needed.
• If ACi > AC’i, then the extracted bit is ‘1’,
• If ACi < AC’i, then the extracted bit is ‘0’.
• Of course, if ACi=AC’i, there is uncertainly about whether the watermark bit is a ‘1’ or ‘0’.
Experimental Results
Experimental Results
Experimental Results
Conclusion• This paper presents a kind of estimation
based blind image watermarking technique.
• Our DCT technique achieves the optimal trade-off among imperceptibility capacity and robustness.