Simg-786 Advanced Digital Image Processing
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
• Invisible: watermark is
perceptually not noticed
and it can be recovered
General Framework for
E(I, S) = J
D(J, R) = S’
Different types of watermarking
• Visible: watermark is a
overlaid into primary
• Invisible-fragile: any
modification of the image
will destroy the
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.
• Invisible Fragile Watermarks
- detect alternation of images stored in a digital library (e.g. human
Attacks on Watermarks
• Lossy Compression
• Geometric Distortions (rotation, translation, scaling and
• Linear and non-linear filtering
• Color reduction
• Addition of noise
• Printing and Rescanning
• And more …
Desired Characteristics of Invisible
• Neither be noticeable to viewer nor degrade
the quality of content.
• Robust, resistant to various intentional
tampering solely intended to remove the
• Watermark should unambiguously identify
• Minimum the amount of pixel modification
Potential Market of Digital
• Web-based vendors selling software, DVD,
CD, video, music
• Medical Imaging application
• Legal documents authentication
Applications of Digital
• 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
• Trade Secrete