robust and transparent watermarking scheme for colour images

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Robust and transparent watermarking scheme for colour imagesSpeaker : Po-Hung Lai

Adviser : Chih-Hung Lin Date : 2009.1.5

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Article History and Author

Article HistoryPublished in IET Image ProcessingReceived on 6th April 2008Revised on 2nd February 2009

AuthorK.-C. Liu & C.-H. Chou

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Outline

Introduction Estimation of JND profiles of colour

images Watermark embedding and extractio

n Simulation results Conclusions

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Introduction

Business

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Introduction

BusinessWATERMARK

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Introduction

WA ARK

圖的正確性 Y?N?

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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 sizessmall number of perceptual works can be fo

und 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 spaceperceptually lossless colour quantisati

on watermark transparencyJNCD threshold

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Introduction (embed part)

Properties of histogramsLin et al. measured the numerous

global features of all pixels and three-dimensional feature space

Invisible watermarking methodcryptographywatermarking

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Introduction (embed part)

Modify pixelsmodifying the intensities of pixels in the blu

e component of the colour image modifying quantisation indices of colour pixels

Spread spectrum watermarking schemewatermark into a four-fork tree in the wavel

et domain of the Y component

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Introduction (defect & improvement)

Fixed step size to quantiseWorse robustness

Modification of the quantisationhelp to improve the performance of the

watermarking scheme.

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Introduction (in this paper)

perceptual redundancy inherentin each wavelet coefficient of the colo

ur 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 ， YCbCrto overcome the non-uniform colour m

etric 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 2.3Performance

of robustness

In CIELAB space use JNCD to embed transparent watermark

Perceptuallylossless colour quantisation

Modifying quantisation indices embedded transparent 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 spaceProvides large perceptual redundancyWithout degrading the visual qualityCan 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 modu

lating 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.