Cryptography Reference
In-Depth Information
Fig. 10.7. Watermarking techniques used for the applications of print-to-web link-
ing technology using mobile phone camera.
10.5 Watermarking Methods
The third kind of method used for the applications of print-to-web linking
technology using mobile phone is the watermarking technique. As shown in
Fig. 10.7, the watermarking methods are generally completed using the fol-
lowing processes.
The embedding process,
(1) Embedding the watermark. This can be an n-bit index to a database of
URL of the images used for the printed media.
(2) Printing the watermarked images onto papers for posters or magazines.
The decoding process,
(1) Capturing the printed image using a mobile camera.
(2) Extracting the watermark from the captured image and retrieving the
corresponding URL in mobile phone or in a retrieve server.
(3) Linking to the website with the retrieved URL and showing the website
page onto the screen of the mobile phone.
The major reason for considering watermarking techniques used for the
application of print-to-web linking technology using mobile phone camera is
that one of the roles of watermarking technology is data hiding [13]. By its
use we can embed the information about URL imperceptibly into an image.
The URL information can then be extracted from the printed image. With
the improvement of robustness in watermarking techniques, it is not a nov-
elty to extract embedded information from a printed image by capturing the
image with a PC-camera. An example of this application is Digimarcs Im-
ageBridge [14]. This was the first application of the watermarking technique
being used for printed media together with a PC-camera or a scanner.
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