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The major topic of this dissertation is how to improve the image quality and application of digital watermarking techniques. Most traditional digital watermarking techniques focus on the development and improvement of embedding algorithm. But fewer people really care about the degradation of the image quality of digital watermarking techniques. Meanwhile, the application of digital watermarking technique seems to be limited in the copyright protection. Therefore, the techniques used to improve the image quality and to expand the application of digital watermarking technique are proposed in this dissertation. The concept of the proposed technique used to improve the image quality of digital watermarking technique is different from the concept of traditional watermarking techniques which directly modify the features of image to embed digital watermark. Dissimilarly, the proposed technique uses the relation between the features to embed the digital watermark. In this way, the probability of modifying the feature can be efficiently reduced. Therefore, the image quality of watermarked image can be improved. Besides, the proposed technique works like a pre-process. The proposed technique can be easily applied to present traditional digital watermarking techniques without changing the original embedding and extracting process. The expansion of digital watermarking techniques application consists of two techniques. The first one uses the digital watermarking technique to provide the ¡§Image Refining¡¨ function for digital images. In the proposed technique, the RS (Reed-Solomon) codes of original image are used as a watermark and are embedded in the original image. The watermarking information can provide the error correction capability while the original image is distorted (refining function). If there is some alterations made to the watermarked image and they are within the error correction capability of the RS parities, the alterations will be corrected by the RS decoding to restore the original image. The second one applies the digital watermarking techniques on the Pay-TV system. Conventional key distribution methods used in Pay-TV system emphasize on the method¡¦s refinement in order to reduce the frequency of the keys distributed over network. The proposed method uses the digital watermarking technique to hide the cryptographic keys into routine encrypted video program without any increasing of video program size for the economy of network bandwidth and degradation in perceptual quality. The purpose of this thesis is to improve the practicability of digital watermarking techniques. The proposed techniques could supplement the incompleteness of the traditional digital watermarking techniques with additional functions and applications. In this way, traditional digital watermarking techniques can not only be used for copyright protection but also be the new choice of resolving problem in the future digital environment.

Das Ziel dieser Untersuchung ist es, Aspekte der Strukturqualität (technische Untersuchungs- und Bildqualität), Prozessqualität (Angemessenheit der Indikation) und der Ergebnisqualität (Richtigkeit der Befunderhebungen) von Röntgenaufnahmen aus der tierärztlichen Praxis zu erörtern und häufige Fehlerquellen festzustellen. Dazu werden alle Röntgenaufnahmen von Kleintieren, die im Zeitraum von Anfang Dezember 2003 bis Ende Dezember 2004 als Original in die Klinik für Kleintiere der Universität Leipzig gelangen auf praxisrelevante Merkmale der Struktur-, Prozess- und Ergebnisqualität hin untersucht. Die Ermittlung der Daten erfolgt auf subjektiver Grundlage anhand eines Befundbogens durch Konsensbeurteilung von zwei Unter-suchern. Zur Auswertung gelangen 1259 Röntgenaufnahmen aus 600 verschiedenen Untersuchungen. Diese Aufnahmen stammen zu 86,9 % aus den Bundesländern Sachsen, Sachsen-Anhalt und Thüringen von 216 verschiedenen Tierarztpraxen. 80,3 % der untersuchten Tiere sind Hunde, 18,9 % Katzen. In der Gesamtbeurteilung der Bildqualität erweisen sich 48,7 % der Aufnahmen ohne Bean-standung. 29,2 % zeigen geringfügige Mängel, 16,0 % sind bedingt diagnostisch geeignet und 6,1 % sind unzureichend. 22,1 % der ausgewerteten Aufnahmen sind somit mangelhaft. Sie weisen Defizite in der diagnostischen Eignung auf oder sind hierfür ungeeignet. Die wichtigsten Fehlerquellen der Strukturqualität sind Mängel der Lagerung und Projektion, des Bildkontrastes und der Bildschärfe. Abweichungen der Lagerung und Projektion, meist durch nicht winkelgerechte Lagerung des Patienten im Direktstrahl verursacht, sind mit 11,4 % aller Aufnahmen im Vergleich zu anderen Fehlerquellen relativ selten. Die Auswirkungen auf die diagnostische Eignung sind jedoch oft schwerwiegend: 69,9 % der von Mängeln in der Lagerung betroffenen Aufnahmen zeigen Einschränkungen hinsichtlich der diagnostischen Eignung. 33,3 % aller Aufnahmen weisen Abweichungen des Bildkontrastes auf. Die häufigste Ursache dafür ist der Umgang mit verbrauchter Entwicklerlösung, gefolgt von Unter- und Überbelichtung. Betrachtet man die Gesamtheit der Kontrastabweichungen kann festgestellt werden, dass 47,7 % auf Fehler in der Filmentwicklung zurückzuführen sind. Auswirkungen auf die Eignung zur Diagnosestellung sind weniger gravierend als bei Mängeln der Lagerung und Projektion: 35,1 % der von Kontrastabweichungen betroffenen Aufnahmen zeigen Einschränkungen des diagnosti-schen Nutzens. 23,0 % der Aufnahmen sind durch Abweichungen der Bildschärfe gekennzeichnet. Am häufigs-ten ist Bewegungsunschärfe (67,7 % der betroffenen Aufnahmen) zu ermitteln. Weiterhin wer-den oft Materialunschärfe und Unschärfe durch Streustrahlung beobachtet, die auf den falschen Umgang mit dem Streustrahlenraster und der Film-Folien-Kombination zurückzuführen sind. Die Auswirkungen auf die diagnostische Eignung zeigen, dass 29,6 % der Röntgenaufnahmen mit Abweichungen der Bildschärfe Einschränkungen des diagnostischen Nutzens nach sich ziehen. Artefakte, vor allem verursacht durch Kratzer, Risse oder Brüche in Film oder Folie sowie durch Verunreinigungen durch Entwickler-, Fixierlösung oder Wasser, sind bei 20,7 % aller Röntgen-aufnahmen zu finden. Einschränkungen der diagnostischen Eignung ergeben sich dadurch bei 1,2 % der analysierten Aufnahmen. Zur Untersuchung der Prozessqualität wird die Angemessenheit der Indikation ermittelt, die nach RöV § 2a für jede Röntgenaufnahme gegeben sein muss (ANON. 2003a). Eine absolute Indikation kann bei 94,7 % der ausgewerteten Aufnahmen festgestellt werden. Bei knapp der Hälfte aller Aufnahmen dieser Arbeit kann die Ergebnisqualität erörtert werden. Die gestellte radiologische Verdachtsdiagnose ist bei 85,5 % dieser Fälle medizinisch nachvoll-ziehbar. Aus den Ergebnissen dieser Arbeit lässt sich ableiten, dass ein wesentlicher Teil der vorkom-menden Mängel der Bildqualität auf ungenügende Sorgfalt bei der Anfertigung und Verarbeitung der Röntgenaufnahme zurückzuführen ist. Allerdings liegen auch Defizite bei der Interpretation der gewonnenen Information durch die Röntgenuntersuchung vor. Da jeder Anwender ionisierender Strahlen verpflichtet ist, jede unnötige Strahlenexposition von Mensch und Umwelt zu vermeiden, müssen bestehende Defizite in Bezug auf die Anwendung der Projektionsradio-grafie abgebaut werden und die Vermittlung von Wissen und praktischen Fertigkeiten auf diesem Gebiet während der tierärztlichen Ausbildung verbessert werden. Ebenso sollte eine Feh-lerbeseitigung durch Ausnutzung oder Verbesserung der technischen Möglichkeiten erfolgen. Eine erneute Untersuchung zur Qualität von Röntgenaufnahmen in der tierärztlichen Praxis auf der Grundlage dieser Studie erscheint zur Überprüfung der getroffenen Maßnahmen zur Ver-besserung der Bildqualität sinnvoll. / The aim of this study is to evaluate aspects of structural quality (technical examination and im-age quality), quality of the process (adequacy of indication) and the outcome (correctness of findings) of radiographs from the veterinary practice and to indentify frequent radiographic er-rors. For this purpose all radiographs of small animals that are received at the Department of Small Animal Medicine of the University of Leipzig between December 1st 2003 and December 31th 2004 as an original are examined for relevant features of structural quality, process quality and outcome. The data collection is done subjectively based on the consensus examination of the radiographs by two independent examiners. The evaluation includes 1259 radiographs from 600 different examinations. 86.9 % of these images come from the federal states of Germany Saxony, Saxony-Anhalt and Thuringia from 216 different veterinary practices. 80.3 % of the examined animals are dogs, 18.9 % are cats. Concerning the over-all evaluation of the image quality, 48.7 % of the radiographs are without restrictions. Minor faults are detected in 29.2 % of the radiographs, 16.0 % are diagnostically compromised and 6.1 % are insufficient. Thus, 22.1 % of the examined radiographs are unsatis-factory. They show either deficits in their diagnostic suitability or are completely useless. The most important sources of errors are faults in positioning of the patient and the following projec-tion, of image contrast and sharpness. Deviations in positioning and projection, mostly caused by a suboptimal angle in the position of the patient in the x-ray, are with 11.4 % of all radiographs in comparison to other errors relatively rare. However the effect on the diagnostic use is severe: 69.9 % of the images with positioning faults show deficits with regard to the diagnostic suitability. Regarding the contrast of the image, 33.3 % of all radiographs display deficits. The most com-mon cause is the use of exhausted developer, followed by under- and overexposure. Consider-ing the overall deviations of image contrast, 47.7 % are attributed to errors during the x-ray film development. Consequences for the diagnostic use are less serious compared to errors in posi-tioning and projection: 35.1 % of the images with contrast deviations are of limited diagnostic use. 23.0 % of the radiographs are characterized by deviations in the sharpness: motion haziness occurs most frequently (in 67.7 %) of the images concerned. Receptor unsharpness and scat-tered radiation are often observed, caused by improper use of radiographic grids and film-screen combinations. The effects on the diagnostic suitability show that 29.6 % of the radiographs with deviations in the sharpness are of limited diagnostic use. Artifacts, most frequently caused by scratches, tears and breaks of the film or the intensifying screen as well as by splashes of the developing resp. fixation reagent or water, are found on 20.7 % of all radiographs. As a result of artifacts 1.2 % of the radiographs examined show defi-cits in their diagnostic suitability. To evaluate the quality of the process the adequacy of indication is determined, which is required for every radiographic examination according to RöV § 2a (ANON. 2003a). An absolute indication can be found in 94.7 % of all images. The quality of the outcome can be discussed in almost halve of all radiographs. The referral diagnosis is medically plausible in 85.5 % of these cases. The results of this study reveal that a considerable portion of the occurring errors in the image quality are caused by a lack of care during taking and processing of the radiographic images. Deficits in the interpretation of the gained information from the radiographic examination occur as well. Since avoidance of unnecessary exposure of humans and the environment to radiation is a major obligation of every user of ionizing radiation, existing deficits regarding the use of projection radiography should be reduced and the transfer of knowledge and practical capabili-ties in this area during the veterinary training should be improved. Furthermore, the elimination of errors by use or improvement of the technical possibilities is important. A new evaluation of the quality of radiographic images from the veterinary practice on the basis of this study seems useful to examine the effects of the steps taken to improve the image quality.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Hasler, Paul; Committee Co-Chair: Degertekin, Levent; Committee Member: Anderson, David; Committee Member: Ayazi, Farrokh; Committee Member: Brand, Oliver; Committee Member: Hesketh, Peter. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Yucel Altunbasak; Committee Member: Brani Vidakovic; Committee Member: Ghassan AlRegib; Committee Member: James Hamblen; Committee Member: Russ Mersereau. Part of the SMARTech Electronic Thesis and Dissertation Collection.

We tackle the problems of no-reference/blind image and video quality evaluation. The approach we take is that of modeling the statistical characteristics of natural images and videos, and utilizing deviations from those natural statistics as indicators of perceived quality. We propose a probabilistic model of natural scenes and a probabilistic model of natural videos to drive our image and video quality assessment (I/VQA) algorithms respectively. The VQA problem is considerably different from the IQA problem since it imposes a number of challenges on top of the challenges faced in the IQA problem; namely the challenges arising from the temporal dimension in video that plays an important role in influencing human perception of quality. We compare our IQA approach to the state of the art in blind, reduced reference and full-reference methods, and we show that it is top performing. We compare our VQA approach to the state of the art in reduced and full-reference methods (no blind VQA methods that perform reliably well exist), and show that our algorithm performs as well as the top performing full and reduced reference algorithms in predicting human judgments of quality. / text

With the increasing number and affordability of image capture devices, there is an increasing demand to objectively analyze and compare the quality of images. Image quality can also be used as an indicator to determine if the source image is of high enough quality to perform analysis on. When applied to real world scenarios, use of a blind algorithm is essential since a flawless reference image typically is unavailable. Recent research has shown promising results in no reference image quality utilizing natural scene statistics in the visual image space. Research has also shown that although the statistical profiles vary slightly, there are statistical regularities in IR images as well which would indicate that natural scene statistical models may be able to be applied. In this project, I will analyze BRISQUE quality features of IR images and determine if the algorithm can successfully be applied to IR images. Additionally, in order to validate the usefulness of these techniques, the BRISQUE quality features are analyzed using a detection algorithm to determine if they can be used to predict conditions which may cause missed detections. / text

Recent image quality assessment (IQA) metrics achieve high correlation with human perception of image quality. Naturally, it is of interest to produce even better results. One promising method is to weight image quality measurements by visual importance. To this end, we describe three strategies - visual fixation-based weighting, quality-based weighting and weighting based on distribution of local quality scores about the mean. By contrast with some prior studies we find that these strategies can improve the correlations with subjective judgment significantly. We demonstrate improvements on the SSIM index in both its multi-scale and single-scale versions, using the LIVE database as a test-bed. / text

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We propose a natural scene statistic based quality assessment model Refer- enceless Image Spatial QUality Evaluator (RISQUE) which extracts marginal statistics of local normalized luminance signals and measures 'un-naturalness' of the distorted image based on measured deviation of them. We also model distribution of pairwise products of adjacent normalized luminance signals providing us with orientation distortion information. Although multi-scale, the model is defined in the space domain avoiding costly frequency or wavelet transforms. The frame work is simple, fast, human perception based and shown to perform statistically better than other proposed no reference algorithms and full reference structural similarity index(SSIM). / text