Digital Image Watermarking

Abate, Yoseph (2005) Digital Image Watermarking. Masters thesis, Addis Ababa University.

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The rapid expansion of the internet in the past years has rapidly increased the availability of digital data such as audio, images and videos to the public. As we have witnessed in the past few years, the problem of protecting multimedia information becomes more and more important and a lot of copyright owners are concerned about protecting any illegal duplication of their data or work. Some serious work needs to be done in order to maintain the availability of multimedia information but, in the meantime, the industry must come up with ways to protect intellectual property of creators, distributors or simple owners of such data. This is an interesting challenge and this is probably why so much attention has been drawn toward the development of digital information protection schemes. Of the many approaches possible to protect visual data, digital watermarking is probably the one that has received most interest. The idea of robust watermarking of images is to embed information data within the image with an insensible form for human visual system but in a way that protects from attacks such as common image processing operations. The goal is to produce an image that looks exactly the same to a human eye but still allows its positive identification in comparison with the owner's key if necessary. This report attempts to first introduce general idea behind digital watermarking as well as some of its basic notions in the first chapter. In chapter two it describes some applications of watermarking techniques. The currently available algorithms are listed from an internet survey for further reference in chapter three. In chapter four the implementation of the Spatial Domain watermarking technique is described in detail. We used the Least Significant Bit Replacement algorithm from the spatial domain watermarking techniques. In chapter five the implementation of Transfer Domain watermarking techniques are described in detail. The famous discrete cosine transform technique, the Cox algorithm, is implemented to show the comparative level of robustness with wavelet watermarking algorithm, the Multiresolution watermarking. Chapter six is dedicated on the concepts of attacks to show how images are exposed to such kinds of distortions. Chapter seven is a conclusion of the application of watermarking techniques in the application of copyright protection, authentication and as a message container. The increasing amount of applications using digital multimedia technologies has accentuated the need to provide copyright protection to multimedia data. Digital watermarking is a method that has received a lot of attention in the past few years. A digital watermark can be described as a visible or preferably invisible identification code that is permanently embedded in the data. It means that it remains present within the data after any decryption process. A general definition for watermarking can be given as: "Hiding of a secret message or information within an ordinary message and the extraction of it at its destination!” Complementary to encryption, it allows some protection of the data after decryption. As we know, encryption procedure aims at protecting the image (or other kind of data) during its transmission. Once decrypted, the image is not protected anymore. By adding watermark, we add a certain degree of protection to the image (or to the information that it contains) even after the decryption process has taken place. The goal is to embed some information in the image without affecting its visual content. In the copyright protection context, watermarking is used to add a key in the multimedia data that authenticates the legal copyright holder and that cannot be manipulated or removed without impairing the data in a way that removes any commercial value. The first distinction that one needs to do in the study of watermarking for digital images is the notion of visible watermarks versus invisible ones. The first ones are used to mark, obviously in a clearly detectable way, a digital image in order to give a general idea of what it looks like while preventing any commercial use of that particular image. The purpose here is to forbid any unauthorized use of an image by adding an obvious identification key, which removes the image’s commercial value. On the other hand, invisible watermarks are used for content and/or author identification in order to be able to determine the origin of an image. They can also be used in unauthorized image’s copies detection either to prove ownership or to identify a customer. The invisible scheme does not intend to forbid any access to an image but its purpose is to be able to tell if a specified image has been used without the owner’s formal consent or if the image has been altered in any way. This approach is certainly the one that has received the most attention in the past couple of years. In that line of thoughts, it is possible to differentiate two ways of embedding invisible information in a digital image.In this report we focused on the invisible watermarking techniques and their implementation with a recommendation of their application areas. The comparative implementation of the Spatial and Transform Domain watermarking techniques are discussed in a very elaborative manner.

Item Type: Thesis (Masters)
Uncontrolled Keywords: Computer Engineering
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
T Technology > T Technology (General)
T Technology > TR Photography
Divisions: Africana
Depositing User: Andriamparany Edilbert RANOARIVONY
Date Deposited: 09 Oct 2018 14:35
Last Modified: 09 Oct 2018 14:35

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