Orientador: Anderson de Rezende Rocha / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-23T03:37:08Z (GMT). No. of bitstreams: 1 Silva_EwertonAlmeida_M.pdf: 20654769 bytes, checksum: cd66fa66dedc48d34c5feb0fa0311759 (MD5) Previous issue date: 2012 / Resumo: Neste trabalho, nós investigamos duas abordagens para detecção de manipulações de Cópia-colagem (Copy-move Forgery) em imagens digitais. A primeira abordagem é baseada no algoritmo PatchMatch Generalizado [4], cuja proposta é encontrar correspondências de patches (blocos de pixels de tamanho definido) em uma ou mais imagens. A nossa abordagem consiste na aplicação do PatchMatch Generalizado em uma dada imagem com o propósito de encontrar, para cada patch desta, um conjunto de patches similares com base nas distâncias de seus histogramas. Em seguida, nós verificamos as correspondências de cada patch para decidir se eles são segmentos de uma região duplicada. A segunda abordagem, que consiste em nossa principal contribuição, é baseada em um processo de Votação e Análise Multiescala da imagem. Dada uma imagem suspeita, extraímos pontos de interesse robustos a operações de escala e rotação, encontramos correspondências entre eles e os agrupamos em regiões com base em certas restrições geométricas, tais como a distância física e a inclinação da reta que os liga. Após a aplicação das restrições geométricas, criamos uma pirâmide multiescala que representará o espaço de escalas da imagem. Nós examinamos, em cada imagem, os grupos criados usando um descritor robusto a rotações, redimensionamentos e compressões. Este processo diminui o domínio de busca de regiões duplicadas e gera um mapa de detecção para cada escala. A decisão final é dada a partir de uma votação entre todos os mapas, na qual um segmento é considerado duplicado se este assim o é na maioria das escalas. Nós validamos ambos os métodos em uma base de imagens que construímos. A base _e composta por 108 clonagens originais e com elevado grau de realismo. Comparamos os métodos propostos com outros do estado da arte nessa mesma base de imagens / Abstract: In this work, we investigate two approaches toward Copy-move Forgery detection in digital images. The first approach relies on the Generalized PatchMatch algorithm [4], which aims at finding patch correspondences in one or more images. Our approach consists in applying the Generalized PatchMatch algorithm in a certain image in order to obtain, for each of its patches, a set of similar patches based on their histogram distances. Next, we check the correspondences of each patch to decide whether or not they are portions of a duplicated region. Our second approach is based on a Voting and Multiscale Analysis process of an image. Given a suspicious image, we extract its interest points robust to scale and rotation transformations and we find possible correspondences among them. Next, we group the correspondent points into regions considering some geometric constraints, such as physical distance and inclination of the line between points of interest. After that, we construct a multiscale pyramid to represent the image scale-space. In each image, we examine the created groups using a descriptor robust to rotation, scaling and compression. This process decreases the search space of duplicated regions and yields a detection map. The final decision depends on a voting among all the detected maps, in which a pixel is considered as part of a manipulation if it is marked as so in the majority of the pyramid scales. We validate both methods using a dataset we have built comprising 108 original and realistic clonings. We compare the proposed methods to others from the state-of-the-art using such cloning dataset / Mestrado / Ciência da Computação / Mestre em Ciência da Computação

Electrical stimulation of the retina affected by photoreceptor loss (e.g., cases of retinitis pigmentosa) elicits the perception of luminous spots (so-called phosphenes) in the visual field. This phenomenon, attributed to the relatively high survival rates of neurons comprising the retina's inner layer, serves as the cornerstone of efforts to provide a microelectronic retinal prosthesis -- a device analogous to the cochlear implant. This thesis concerns phosphenes -- their elicitation and modulation, and, in turn, image analysis for use in a prosthesis. This thesis begins with a comparative review of visual modelling of electrical epiretinal stimulation and analogous acoustic modelling of electrical cochlear stimulation. The latter models involve coloured noise played to normal listeners so as to investigate speech processing and electrode design for use in cochlear implants. Subsequently, four experiments (three psychophysical and one numerical), and two statistical analyses, are presented. Intrinsic signal optical imaging in cerebral cortex is canvassed appendically. The first experiment describes a visual tracking task administered to 20 normal observers afforded simulated prosthetic vision. Fixation, saccade, and smooth pursuit, and the effect of practice, were assessed. Further, an image analysis scheme is demonstrated that, compared to existing approaches, assisted fixation and pursuit (but not saccade) accuracy (35.8% and 6.8%, respectively), and required less phosphene array scanning. Subsequently, (numerical) information-theoretic reasoning is provided for the scheme's superiority. This reasoning was then employed to further optimise the scheme (resulting in a filter comprising overlapping Gaussian kernels), and may be readily extended to arbitrary arrangements of many phosphenes. A face recognition study, wherein stimuli comprised either size- or intensity-modulated phosphenes, is then presented. The study involved unpracticed observers (n=85), and showed no 'size' --versus--'intensity' effect. Overall, a 400-phosphene (100-phosphene) image afforded subjects 89.0% (64.0%) correct recognition (two-interval forced-choice paradigm) when five seconds' scanning was allowed. Performance fell (64.5%) when the 400-phosphene image was stabilised on the retina and presented briefly. Scanning was similar in 400- and 100-phosphene tasks. The final chapter presents the statistical effects of sampling and rendering jitter on the phosphene image. These results may generalise to low-resolution imaging systems involving loosely packed pixels.

Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Rusell M. Mersereau; Committee Member: Biing Hwang (Fred) Juang; Committee Member: Christopher E. Heil; Committee Member: Georgia Vachtsevanos; Committee Member: James H. McClellan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Electrical stimulation of the retina affected by photoreceptor loss (e.g., cases of retinitis pigmentosa) elicits the perception of luminous spots (so-called phosphenes) in the visual field. This phenomenon, attributed to the relatively high survival rates of neurons comprising the retina's inner layer, serves as the cornerstone of efforts to provide a microelectronic retinal prosthesis -- a device analogous to the cochlear implant. This thesis concerns phosphenes -- their elicitation and modulation, and, in turn, image analysis for use in a prosthesis. This thesis begins with a comparative review of visual modelling of electrical epiretinal stimulation and analogous acoustic modelling of electrical cochlear stimulation. The latter models involve coloured noise played to normal listeners so as to investigate speech processing and electrode design for use in cochlear implants. Subsequently, four experiments (three psychophysical and one numerical), and two statistical analyses, are presented. Intrinsic signal optical imaging in cerebral cortex is canvassed appendically. The first experiment describes a visual tracking task administered to 20 normal observers afforded simulated prosthetic vision. Fixation, saccade, and smooth pursuit, and the effect of practice, were assessed. Further, an image analysis scheme is demonstrated that, compared to existing approaches, assisted fixation and pursuit (but not saccade) accuracy (35.8% and 6.8%, respectively), and required less phosphene array scanning. Subsequently, (numerical) information-theoretic reasoning is provided for the scheme's superiority. This reasoning was then employed to further optimise the scheme (resulting in a filter comprising overlapping Gaussian kernels), and may be readily extended to arbitrary arrangements of many phosphenes. A face recognition study, wherein stimuli comprised either size- or intensity-modulated phosphenes, is then presented. The study involved unpracticed observers (n=85), and showed no 'size' --versus--'intensity' effect. Overall, a 400-phosphene (100-phosphene) image afforded subjects 89.0% (64.0%) correct recognition (two-interval forced-choice paradigm) when five seconds' scanning was allowed. Performance fell (64.5%) when the 400-phosphene image was stabilised on the retina and presented briefly. Scanning was similar in 400- and 100-phosphene tasks. The final chapter presents the statistical effects of sampling and rendering jitter on the phosphene image. These results may generalise to low-resolution imaging systems involving loosely packed pixels.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Piyush Kumar, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed June 7, 2006). Document formatted into pages; contains viii, 45 pages. Includes bibliographical references.

This thesis represents Bayesian joint audio-visual tracking for the 3D locations of multiple people and a current speaker in a real conference environment. To achieve this objective, it focuses on several different research interests, such as acoustic-feature detection, visual-feature detection, a non-linear Bayesian framework, data association, and sensor fusion. As acoustic-feature detection, time-delay-of-arrival~(TDOA) estimation is used for multiple source detection. Localization performance using TDOAs is also analyzed according to different configurations of microphones. As a visual-feature detection, Viola-Jones face detection is used to initialize the locations of unknown multiple objects. Then, a corner feature, based on the results from the Viola-Jones face detection, is used for motion detection for robust objects. Simple point-to-line correspondences between multiple cameras using fundamental matrices are used to determine which features are more robust. As a method for data association and sensor fusion, Monte-Carlo JPDAF and a data association with IPPF~(DA-IPPF) are implemented in the framework of particle filtering. Three different tracking scenarios of acoustic source tracking, visual source tracking, and joint acoustic-visual source tracking are represented using the proposed algorithms. Finally the real-time implementation of this joint acoustic-visual tracking system using a PC, four cameras, and six microphones is addressed with two parts of system implementation and real-time processing.

Tato práce popisuje problematiku návrhu a vývoje aplikace pro rekonstrukci 3D modelů z 2D obrazových dat, označované jako bundle adjustment. Práce analyzuje proces 3D rekonstrukce a důkladně popisuje jednotlivé kroky. Prvním z kroků je automatizované získání obrazové sady z internetu. Je představena sada skriptů pro hromadné stahování obrázků ze služeb Flickr a Google Images a shrnuty požadavky na tyto obrázky pro co nejlepší 3D rekonstrukci. Práce dále popisuje různé detektory, extraktory a párovací algoritmy klíčových bodů v obraze s cílem najít nejvhodnější kombinaci pro rekonstrukci budov. Poté je vysvětlen proces rekonstrukce 3D struktury, její optimalizace a jak je tato problematika realizovaná v našem programu. Závěr práce testuje výsledky získané z implementovaného programu pro několik různých datových sad a porovnává je s výsledky ostatních podobných programů, představených v úvodu práce.