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
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
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
Carrier Implementation 2Carrier Implementation 2High-pass vs. All-passHigh-pass vs. All-pass
Carrier Implementation 3Carrier Implementation 3
• Auto correlation of Carrier function should approximate delta function
• The average of Carrier should be 0
Carrier Implementation 4Carrier Implementation 4if Carrier is not symmetric in frequency domainif Carrier is not symmetric in frequency domain
Embedded MessageEmbedded Message
*• Convolution is
implemented by multiplication of Fourier transform in frequency domain
• Zero padding must be performed before FFT
Tiling Improves the RobustnessTiling Improves the Robustness
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
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
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
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
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
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
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
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
Rotation/Scale DetectionRotation/Scale DetectionThreshold and image DilationThreshold and image Dilation
Rotation/Scale DetectionRotation/Scale DetectionImage rotationImage rotation
Rotation/Scale DetectionRotation/Scale DetectionImage rotationImage rotation
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
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
Thank You!Thank You!
Question?Question?
Top Related