21-06-2014, 12:18 PM
A DCT-BASED digital watermarking Algorithm FOR Image
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INTRODUCTION
With the rapid development of information technology
and the wide application of network, the protection of
copyright ownership becomes more and more necessary.
The conventional information encryption is not safe enough
because the document can be copied and distributed easily.
As a new method against the failure of encryption, digital
watermarking has been proposed as an effective way to
protect the ownership of digital documents, especially the
ownership of digital images. Digital watermarking
techniques for image have been wildly researched in recent
years. There are two different watermarking techniques for
image[1], spatial domain techniques[2] and frequency domain
techniques[3][4]. The watermarking is embedded straightly
into an image in the spatial domain[5]. The simplest method
is the LSB (least significant bit) algorithm, in which the
watermarking information is embedded into the LSB or
multiple bit layers of image. By contrast, in the frequency
domain, the original image is first transformed into the
frequency, and then the transformed coefficients are
modified by the information of watermarking. One of the
most typical frequency domain watermarking techniques is
based on DCT(discrete fractional Fourier transform), which
is robust to compression, filter and other transformation on
image, and is compatible with the JPEG compression. The
digital watermarking techniques based on DCT have been
researched widely.
II. PREVIOUS WORK
A. Watermarking Techniques for Image in Spatical
Domain
1) LSB Algorithms
Single LSB Algorithm is the simplest watermarking
techniqueˈby which watermarking information w