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Digital watermarking is the process of embedding information
into digital multimedia content like image, audio, video or text such that the watermark
information can be extracted later for different purposes including copy prevention
and control.
Generally it is used to insert the copyright information of the data.
A digital watermark can be
(a) Visible
(b) Invisible
The visible watermark generally consists of a visible message
indicating the ownership of the image.
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The invisible watermark can only be determined using
an appropriate watermark extraction algorithm.
Generally invisible watermarking
technique consists of an encoding process and a decoding process. Invisible watermarking
schemes can be classified as either
(a) Robust
(b) Fragile
Robust watermarks are often used to prove ownership
claims and so are generally designed to withstand common image processing tasks
such as compression, cropping, scaling, filtering, contrast enhancement, printing,
scanning, etc., in addition to malicious attacks aimed at removing or forging the
watermark.
Fragile watermarks are designed to be distorted by the
slightest changes to the image.
Image watermarking
The digital age made it easy the process of delivering
content and at which the buyer can re-distribute the content which decreases the
income to the seller.
Example: Images placed on the internet.
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Audio watermarking
The process of embedding information into audio can be
termed as audio watermarking. Same as other kinds of data audio contains a carrier
for physo-acoustically hidden data.
Video watermarking
Video watermarking is the process of watermarking the sequence of
video frames.
The raw frame data or the compressed data can be watermarked. Videos
are nothing but the stream of individual images.
So, all image watermarking techniques
can be equally applicable to video when the individual frames are treated as images.
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