Fast_Digital_Watermarking_Techniques_for_Still_Imagesn -...

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Fast Digital Watermarking Techniques for Still Images Mohamed A. Mohamed 1 , Mohy El-Din A. Abou-Soud 1 , Mai S. Diab 2 1 Communications Engineering Department, Faculty of Engineering, Mansoura University 2 Computer Systems Department, Faculty of Computer Science, Benha University Abstract - In this paper, we investigate the problem of choosing the best domain for embedding watermarks in digital still images. During this paper, twelve watermarking techniques were implemented and evaluated. Four techniques were selected to represent different approaches of embedding data in spatial domain, three approaches using discrete cosine transform (DCT) domain, two approaches using discrete wavelet transform domain (DWT) domain, and two combined DWT-DCT techniques. The algorithms were chosen to represent a range of computational complexities and implementation structures. The performance of the selected algorithms was evaluated with respect to many perceptibility parameters. Keywords: Watermarking, Code division Multiple Access (CDMA), Wavelets. I. INTRODUCTION In the recent time, the rapid and extensive growth in Internet technology is creating a pressing need to develop several newer techniques to protect copyright, ownership and content integrity of digital media. This necessity arises because the digital representation of media possesses inherent advantages of portability, efficiency and accuracy of information content in one hand, but on the other hand, this representation also puts a serious threat of easy, accurate and illegal perfect copies of unlimited number. Unfortunately the currently available formats for image, audio and video in digital form do not allow any type of copyright protection. A potential solution to this kind of problem is a digital watermarking which is intended to complement cryptographic process [1]. While the later technique facilitates access of the encrypted data only for valid key holders but fails to track any reproduction or retransmission of data after decryption. On the other hand, in digital watermarking, an identification code is embedded permanently inside a cover image which remains within that cover invisibly even after decryption process. This requirement of watermarking technique, in general, needs to possess the following characteristics: (a) imperceptibility for hidden information, (b) redundancy in distribution of the hidden information inside the cover image to satisfy robustness in watermark extraction process even from the cropped watermarked image. In general, watermark must also be highly robust, entirely resistant to distortion introduced during either normal use (unintentional attack), or a deliberate attempt to disable or remove the watermark present (intentional, or malicious attack). Unintentional attacks involve transforms that are commonly applied to images during normal use, such as cropping, resizing, contrast enhancement…etc. A particularly interesting form of unintentional attack is that of image
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This note was uploaded on 07/16/2009 for the course FCI 123 taught by Professor Sedf during the Spring '08 term at Cairo University.

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Fast_Digital_Watermarking_Techniques_for_Still_Imagesn -...

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