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Robust and transparent
watermarking scheme for colour
images
Speaker : Po-Hung Lai
Adviser : Chih-Hung Lin
Date : 2009.1.5
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Article History and Author
Article History
 Published in IET Image Processing
 Received on 6th April 2008
 Revised on 2nd February 2009
 Author
 K.-C. Liu & C.-H. Chou

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Outline
 Introduction
 Estimation
of JND profiles of colour
images
 Watermark embedding and
extraction
 Simulation results
 Conclusions
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Introduction
Business
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Introduction
Business
WATERMARK
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Introduction
圖的正確性
Y?N?
WA
ARK
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Introduction
 texture,
luminance, corner and edge
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Introduction (visual part)
 discrete
cosine transform (DCT)
by Watson’s perceptual model Li et al.
 adaptively adjust quantisation step sizes
 small number of perceptual works can be
found

 Human

Visual System (HVS)
watermark was inserted into the perceptually
important sub-image
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Introduction (visual part)
 Just
noticeable colour difference
(JNCD)
 in
the uniform CIELAB colour space
 perceptually lossless colour
quantisation watermark transparency
 JNCD threshold
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Introduction (embed part)
 Properties
of histograms
 Lin
et al. measured the numerous
global features of all pixels and threedimensional feature space
 Invisible
watermarking method
 cryptography
 watermarking
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Introduction (embed part)
 Modify
pixels

modifying the intensities of pixels in the
blue component of the colour image

modifying quantisation indices of colour pixels
 Spread
spectrum watermarking
scheme

watermark into a four-fork tree in the
wavelet domain of the Y component
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Introduction (defect & improvement)
 Fixed
step size to quantise
 Worse
robustness
 Modification
of the quantisation
 help
to improve the performance of the
watermarking scheme.
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Introduction (in this paper)
 perceptual
redundancy inherent
 in
each wavelet coefficient of the
colour image in a more reliable YCbCr
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Estimation of JND profiles of
colour images
 Tristimulus
values
 Perceptually indistinguishable.
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Estimation of JND profiles of colour
images
 Color
space，CIELAB
(Commission International L’E’ clairage)
 RGB，YUV，YCbCr
 to overcome the non-uniform colour
metric that had been discussed by
MacAdam
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Estimation of JND profiles of colour
images
JNCD
In CIELAB space any two colours
difference is greater than 2.3
Performance In CIELAB space use JNCD to
of
embed transparent watermark
robustness
Perceptually Modifying quantisation indices
lossless colour embedded transparent
quantisation watermark
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Estimation of JND profiles of
colour images
 adaptive

JNCD (AJNCD)
due to local variations in luminance
magnitude is considered to estimate
the adaptive JNCD (AJNCD) for each
colour pixel
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Estimation of JND profiles of colour
images
is a weighting function
between AJNCD

is the average background
luminance


is the maximum of the four weighted
average of luminance
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Estimation of JND profiles of colour
images
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Estimation of JND profiles of colour
images
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Estimation of JND profiles of colour
images
Luminance contrast is given by f1
 texture masking effect is given by f2

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Estimation of JND profiles of colour
images
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Estimation of JND profiles of colour
images
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Estimation of JND profiles of colour
images
 Choose
YCbCr colour space
 Provides
large perceptual redundancy
 Without degrading the visual quality
 Can resist JPEG，JPEG2000，H.26x
compression attacks
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Estimation of JND profiles of colour
images

is the JND threshold
is the MND threshold

is a lifting factor
 minimally noticeable distortion (MND)

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Estimation of JND profiles of colour
images
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Watermark embedding and extraction
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Watermark embedding and extraction
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Watermark embedding and extraction
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Watermark embedding and extraction
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Watermark embedding and extraction

is the energy of the estimated JND
profile
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Watermark embedding and extraction

The plots of relative distortion capacity
versus band number are obtained
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Watermark embedding and extraction
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Watermark embedding and extraction
To guarantee the transparency and
robustness
 JND




tuned by the associated JND value
key information
facilitate the portability of key
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Watermark embedding and extraction

full-band JND profiles




Bitstream image is too bad
JPEG2000 coder
reduced to 1 k bytes
Sub-band JND profile


tuned colour quantisation
JNDs decodedwatermarked coefficients
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Watermark embedding and extraction


= quantisation index
= quantisation step size
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Watermark embedding and extraction

= decoded JND threshold
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Watermark embedding and extraction



， B=bit sequence
= binary value of 1 or 0
is a random value of 1 or 21 for
modulating qZ,i to higher or lower index
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Watermark embedding and extraction
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Simulation results
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Simulation results
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Simulation results

To verity the robustness
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Simulation results
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Simulation results
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Simulation results
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Simulation results

Second experiment
Huang et al.
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Simulation results

Stimark software
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Simulation results
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Simulation results
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Simulation results
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Simulation results
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Simulation results
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Conclusions

By using the perceptual redundancy
Watermark transparency is achieved
 Quite robust in the face of various attacks.

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