AbstractsComputer Science

Image watermarking consitutes one of the hot topics in the media security area during the last decades. Its scope is to ensure the integrity, authority and authenticity of images by incorporating information for further identification. Researchers tend to focus on the transform domain type of methods, but the major question that rises is why a watermarking method should use the frequency domain coefficients to “seal” their significant information within the media. The basic reason is that the frequency domain manages to better capture the characteristics of the Human Visual System (HVS) leading to high visual quality watermarked images (imperceptibility). Specifically, the low order coefficients describe the coarse part of the content in contrast with the higher order that describe the image details. The second reason is related with the robustness of a number of transformations under noisy conditions or geometric distortions. The latter can significanlty enhance the security provided by the specific transformations. However, an advanced up-to-date image watermarking method should satisfy all four basic requirements of robustness, imperceptibility, capacity and complexity. As a matter of fact, a simple implemented/fast (low complexity) watermarking method should incorporate the maximum allowed amount of information (high capacity) to the host image according to the perceptual redundancy (high imperceptibility) surviving also any geometric or signal processing attacking condition (high robustness). The traditional tradeoff between the aforementioned requirements can be eliminated by the image moments that constitute one of the most attractive transformations nowadays. The specific transformation is lately applied to image watermarking providing high quality services due to their strong description capabilities. The main contribution of this research is to locate and highlight any perspectives or challenges of the specific area with respect to the application of image moments providing also the corresponding solutions to the image watermarking community. The basic challenges / issues in moment-based image watermarking have not been reported since now. The lack of a review / performance evaluation work that examines the results of a number of milestone works with respect to the basic requirements should constitute the initial step of a “fresh” researcher that would lead him to the identification of any existing challenges / issues. The dissertation is divided in 8 chapters. [...] Η ψηφιακή υδατογράφηση εικόνων αποτελεί ένα από τα πιο επίκαιρα θέματα στο χώρο της ασφάλειας δεδομένων τις τελευταίες δεκαετίες. Ο σκοπός της είναι να εξασφαλίσει την ακεραιότητα, την κυριότητα και αυθεντικότητα των εικόνων ενσωματώνοντας πληροφορία για περεταίρω ταυτοποίηση. Οι ερευνητές του χώρου εστιάζουν σε πεδία που προκύπτουν από μετασχηματισμούς και το βασικό ερώτημα που προκύπτει συνδέεται άμεσα με την αναζήτηση των λόγων που τους οδηγούν στη συγκεκριμένη επιλογή. Ο βασικός λόγος είναι η καλύτερη περιγραφή των χαρακτηριστικών του…