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Page 1: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Digital Watermarking Using Phase Digital Watermarking Using Phase Dispersion --- UpdateDispersion --- Update

SIMG 786 SIMG 786

Advanced Digital Image ProcessingAdvanced Digital Image Processing

Mahdi Nezamabadi, Mahdi Nezamabadi,

Chengmeng Liu, Chengmeng Liu,

Michael SuMichael Su

Page 2: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

OutlineOutline

• Carrier design

• Embedding and extraction for single tile and Multi-tiles (improving the robustness)

• Parameter α selection and invisibility

• Moment Normalization• Rotation/Scale Detection

Page 3: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Carrier Implementation 1Carrier Implementation 1

• Carrier is implemented in frequency domain

• Carrier has random phase

• The amplitude of Carrier is high pass in order to make it invisible in spatial domain

• Carrier should be symmetric in frequency domain in order to make its imaginary part to 0 in spatial domain

Page 4: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Carrier Implementation 2Carrier Implementation 2High-pass vs. All-passHigh-pass vs. All-pass

Page 5: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Carrier Implementation 3Carrier Implementation 3

• Auto correlation of Carrier function should approximate delta function

• The average of Carrier should be 0

Page 6: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Carrier Implementation 4Carrier Implementation 4if Carrier is not symmetric in frequency domainif Carrier is not symmetric in frequency domain

Page 7: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Embedded MessageEmbedded Message

*• Convolution is

implemented by multiplication of Fourier transform in frequency domain

• Zero padding must be performed before FFT

Page 8: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Tiling Improves the RobustnessTiling Improves the Robustness

Page 9: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Tiling Improves the RobustnessTiling Improves the Robustness

• After 8 by 8 tiling, the summation of tiles is shown at right

• The amplitude of the input image will be averaged to flatten after summation of 64 tiles

• The watermark information is amplified

Page 10: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Parameter Parameter αα = 0.1 = 0.1

αα = 0.05 = 0.05 αα = 0.1 = 0.1 αα = 0.3 = 0.3 αα = 0.5 = 0.5 αα = 0.7 = 0.7

Page 11: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Parameter Parameter αα = 0.3 = 0.3

αα = 0.05 = 0.05 αα = 0.1 = 0.1 αα = 0.3 = 0.3 αα = 0.5 = 0.5 αα = 0.7 = 0.7

Page 12: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Parameter Parameter α = 0.5 = 0.5

αα = 0.05 = 0.05 αα = 0.1 = 0.1 αα = 0.3 = 0.3 αα = 0.5 = 0.5 αα = 0.7 = 0.7

Page 13: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Parameter Parameter α = 0.7 = 0.7

αα = 0.05 = 0.05 αα = 0.1 = 0.1 αα = 0.3 = 0.3 αα = 0.5 = 0.5 αα = 0.7 = 0.7

Page 14: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Similarity vs. Similarity vs. α

• Similarity is measured by cross correlation between original and extracted log

• 64 tiles were used in embedding

• The α controls the visibility of the watermark logo in the watermarked image

• The α also depends on the number of tiles

Page 15: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Attacked by low pass filterAttacked by low pass filter

• The watermarked image is blurred

• The extracted logo is equivalent to original log convolve with a low pass filter

α=0.3,no blurred α=0.3,blurred

Page 16: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Moment NormalizationMoment Normalization

• Preprocessing to remove the high amplitude, low frequency noise

• At flat area, v’ is replaced by random number with variance of σd

Page 17: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Rotation/Scale DetectionRotation/Scale DetectionThreshold and image DilationThreshold and image Dilation

Page 18: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Rotation/Scale DetectionRotation/Scale DetectionImage rotationImage rotation

Page 19: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Rotation/Scale DetectionRotation/Scale DetectionImage rotationImage rotation

Page 20: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Current Issues and ProblemsCurrent Issues and Problems

• Odd and Even dimensions of Carrier function generate different output result in spatial domain.

• How to deal with interpolation errors during rescaling and re-rotation processes

Page 21: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Follow-up WorksFollow-up Works

• Implement Contrast Sensitivity Function in Carrier function design

• Rotation/Scale pattern detection • Rotate back to right orientation and scale back

to its original dimensions• Implementation of Binary Message template

function• Integrate all functions and final presentation and

report

Page 22: Digital Watermarking Using Phase Dispersion --- Update SIMG 786 Advanced Digital Image Processing Mahdi Nezamabadi, Chengmeng Liu, Michael Su.

Thank You!Thank You!

Question?Question?


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