1 Robust and transparent watermarking scheme for colour images Speaker : Po-Hung Lai Adviser : Chih-Hung Lin Date : 2 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 3 Outline Introduction Estimation of JND profiles of colour images Watermark embedding and extraction Simulation results Conclusions 4 Introduction Business 5 Introduction Business WATERMARK 6 Introduction WA ARK Y?N? 7 Introduction texture, luminance, corner and edge 8 Introduction (visual part) discrete cosine transform (DCT) by Watsons 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 9 Introduction (visual part) Just noticeable colour difference (JNCD) in the uniform CIELAB colour space perceptually lossless colour quantisation watermark transparency JNCD threshold 10 Introduction (embed part) Properties of histograms Lin et al. measured the numerous global features of all pixels and three- dimensional feature space Invisible watermarking method cryptography watermarking 11 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 12 Introduction (defect & improvement) Fixed step size to quantise Worse robustness Modification of the quantisation help to improve the performance of the watermarking scheme. 13 Introduction (in this paper) perceptual redundancy inherent in each wavelet coefficient of the colour image in a more reliable YCbCr 14 Estimation of JND profiles of colour images Tristimulus values Perceptually indistinguishable. 15 Estimation of JND profiles of colour images Color space CIELAB (Commission International LE clairage ) RGB YUV YCbCr to overcome the non-uniform colour metric that had been discussed by MacAdam 16 Estimation of JND profiles of colour images JNCD In CIELAB space any two colours difference is greater than 2.3 Performance of robustness In CIELAB space use JNCD to embed transparent watermark Perceptually lossless colour quantisation Modifying quantisation indices embedded transparent watermark 17 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 18 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 19 Estimation of JND profiles of colour images 20 Estimation of JND profiles of colour images 21 Estimation of JND profiles of colour images Luminance contrast is given by f1 texture masking effect is given by f2 22 Estimation of JND profiles of colour images 23 Estimation of JND profiles of colour images 24 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 25 Estimation of JND profiles of colour images is the JND threshold is the MND threshold is a lifting factor minimally noticeable distortion (MND) 26 Estimation of JND profiles of colour images 27 Watermark embedding and extraction 28 Watermark embedding and extraction 29 Watermark embedding and extraction 30 Watermark embedding and extraction 31 Watermark embedding and extraction is the energy of the estimated JND profile 32 Watermark embedding and extraction The plots of relative distortion capacity versus band number are obtained 33 Watermark embedding and extraction 34 Watermark embedding and extraction To guarantee the transparency and robustness JND tuned by the associated JND value key information facilitate the portability of key 35 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 36 Watermark embedding and extraction = quantisation index = quantisation step size 37 Watermark embedding and extraction = decoded JND threshold 38 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 39 Watermark embedding and extraction 40 Simulation results 41 Simulation results 42 Simulation results To verity the robustness 43 Simulation results 44 Simulation results 45 Simulation results 46 Simulation results Second experiment Huang et al. 47 Simulation results Stimark software 48 Simulation results 49 Simulation results 50 Simulation results 51 Simulation results 52 Simulation results 53 Conclusions By using the perceptual redundancy Watermark transparency is achieved Quite robust in the face of various attacks.