08-05-2012, 01:03 PM
Invisible Digital Image Watermarking
watermarking.ppt (Size: 1.74 MB / Downloads: 519)
Applications
Copyright Protection
Invisibly mark products
Manage distribution of assets
Apply unique watermark key to each copy of a distributed video/image
Embed all necessary data in a single image
Naturally expands to video watermarking
Robustness
Fragile
Detection fails with even minor modification
Useful in tampering detection
Common in simple additive watermarking
Robust
Detection is accurate even under modification
Need for robustness dependent on use of data
Verification / Detection Methods
Non-blind
The watermarking scheme requires the use of the original image
Semi-Blind
The watermarking scheme requires the watermark data and/or the parameters used to embed the data
Blind
If the watermarking scheme does not require the original image or any other data
Watermark Embedding Method
Perform 2D-DWT to divide image into LL, HL, LH and HH sub-bands.
Select coefficients from the LL, HL, LH and HH sub-bands that surpass a particular threshold T1
Embed watermarking data via additive modification
t’i = ti + α|ti|xi