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					Digital Watermarking
Simg-786 Advanced Digital Image Processing

               Team 1
What is digital watermarking?
               • Digital watermarking is
                 the process that embeds
                 data called a watermark or
                 digital signature or tag or
                 label into a multimedia
                 object such that
                 watermark can be detected
                 or extracted later to make
                 an assertion about object.
               • It is widely used in
                 Copyright Marking
               • Invisible: watermark is
                 perceptually not noticed
                 and it can be recovered
General Framework for
    watermarking
               E(I, S) = J

               D(J, R) = S’
Different types of watermarking
                • Visible: watermark is a
                  secondary translucent
                  overlaid into primary
                  image.
                • Invisible-fragile: any
                  modification of the image
                  will destroy the
                  watermark.
Application of Digital Watermark
• Visible watermarks:
 - for enhanced copyright protection. Images will be used commercially
   (e.g. imprinting coffee mugs) without payment of royalties.
- used to indicate ownership originals (e.g. library manuscript).
• Invisible Robust watermarks:
- detect misappropriated images.
- as evidence of ownership.
- identification
• Invisible Fragile Watermarks
- detect alternation of images stored in a digital library (e.g. human
   fingerprints).
         Attacks on Watermarks
• Lossy Compression
• Geometric Distortions (rotation, translation, scaling and
  cropping)
• Resampling
• Requantization
• Linear and non-linear filtering
• Color reduction
• Addition of noise
• Printing and Rescanning
• Rewatermarking
• And more …
 Desired Characteristics of Invisible
        Robust Watermarks
• Neither be noticeable to viewer nor degrade
  the quality of content.
• Robust, resistant to various intentional
  tampering solely intended to remove the
  watermark.
• Watermark should unambiguously identify
  the owner
• Minimum the amount of pixel modification
     Potential Market of Digital
             Watermark
• Web-based vendors selling software, DVD,
  CD, video, music
• Medical Imaging application
• Legal documents authentication
         Applications of Digital
            Watermarking
• Intellectual Properties Protection
• Embed visible, invisible or both trademarks,
  copyright statement on computer software, digital
  images, videos, documents. Users won’t be able to
  steal the owner’s property, the embedded
  watermark will prove the ownership.
• Combined with data encryption technique, more
  restrictions can be imposed to authorized users
         Intellectual Properties
•   Copyright
•   Trademark
•   Patent
•   Trade Secrete

				
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posted:10/3/2011
language:English
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Jun Wang Jun Wang Dr
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