Global ETD Search

41	Simplified fixed pattern noise correction and image display for high dynamic range CMOS logarithmic imagers Otim, Stephen O. January 2007 (has links) Biologically inspired logarithmic CMOS sensors offer high dynamic range imaging capabilities without the difficulties faced by linear imagers. By compressing dynamic range while encoding contrast information, they mimic the human visual system’s response to photo stimuli in fewer bits than those used in linear sensors. Despite this prospect, logarithmic sensors suffer poor image quality due to illumination dependent fixed pattern noise (FPN), making individual pixels appear up to 100 times brighter or darker. This thesis is primarily concerned with alleviating FPN in logarithmic imagers in a simple and convenient way while undertaking a system approach to its origin, distribution and effect on the quality of monochrome and colour images, after FPN correction. Using the properties of the Human visual system, I propose to characterise the errors arising from FPN in a perceptually significant manner by proposing an error measure, never used before. Logarithmic operation over a wide dynamic range is first characterised using a new model; yi j =aj +bj ln(exp sqrt(cj +djxi)−1), where yi j is the response of the sensor to a light stimulus xi and aj, bj, cj and dj are pixel dependent parameters. Using a proposed correction procedure, pixel data from a monochromatic sensor array is FPN corrected to approximately 4% error over 5 decades of illumination even after digitisation - accuracy equivalent to four times the human eyes ability to just notice an illumination difference against a uniform background. By evaluating how error affects colour, the possibility of indiscernible residual colour error after FPN correction, is analytically explored using a standard set of munsell colours. After simulating the simple FPN correction procedure, colour quality is analysed using a Delta E76 perceptual metric, to check for perceptual discrepancies in image colour. It is shown that, after quantisation, the FPN correction process yields 1−2 Delta E76 error units over approximately 5 decades of illumination; colour quality being imperceptibly uniform in this range. Finally, tone-mapping techniques, required to compress high dynamic range images onto the low range of standard screens, have a predominantly logarithmic operation during brightness compression. A new Logr'Gb' colour representation is presented in this thesis, significantly reducing computational complexity, while encoding contrast information. Using a well-known tone mapping technique, images represented in this new format are shown to maintain colour accuracy when the green colour channel is compressed to the standard display range, instead of the traditional luminance channel. The trade off between colour accuracy and computation in this tone mapping approach is also demonstrated, offering a low cost alternative for applications with low display specifications. 005.3
42	Skládání HDR obrazu pro pohyblivou scénu / HDR Composition for Dynamic Scene Martinů, Lukáš January 2015 (has links) Master's thesis is focused on capturing of low dynamic range images using common devices such as camera and its multiple exposure. The main part of thesis is dedicated to composing these images to HDR image, inclusive sequence of images of static scenes, but also dynamic ones. Next part describes tone mapping used for display HDR image on LDR monitors. Moreover, there is given design and implementation of application solving problems mentioned earlier. In the end, the implemented application is evaluated and the possible continuation of this work is stated.
43	Snímání a zpracování digitálních obrazů s vysokým dynamickým rozsahem / Acquisition and Processing of Digital Images with High Dynamic Range Mrázek, Zdeněk January 2016 (has links) The target of this thesis is sumarize the theory of metods used for composition image sequence into single high dynamic range image. Selected methods and algorithms are described in theoretical part and implemented in practical part of this thesis. It was used C++ language with using OpenCV library.
44	La décomposition automatique d'une image en base et détail : Application au rehaussement de contraste / The automatic decomposition of an image in base and detail : Application to contrast enhancement Hessel, Charles 07 May 2018 (has links) Dans cette thèse CIFRE en collaboration entre le Centre de Mathématiques et de leurs Applications, École Normale Supérieure de Cachan et l’entreprise DxO, nous abordons le problème de la décomposition additive d’une image en base et détail. Une telle décomposition est un outil fondamental du traitement d’image. Pour une application à la photographie professionnelle dans le logiciel DxO Photolab, il est nécessaire que la décomposition soit exempt d’artefact. Par exemple, dans le contexte de l’amélioration de contraste, où la base est réduite et le détail augmenté, le moindre artefact devient fortement visible. Les distorsions de l’image ainsi introduites sont inacceptables du point de vue d’un photographe.L’objectif de cette thèse est de trouver et d’étudier les filtres les plus adaptés pour effectuer cette tâche, d’améliorer les meilleurs et d’en définir de nouveaux. Cela demande une mesure rigoureuse de la qualité de la décomposition en base plus détail. Nous examinons deux artefact classiques (halo et staircasing) et en découvrons trois autres types tout autant cruciaux : les halos de contraste, le cloisonnement et les halos sombres. Cela nous conduit à construire cinq mire adaptées pour mesurer ces artefacts. Nous finissons par classer les filtres optimaux selon ces mesures, et arrivons à une décision claire sur les meilleurs filtres. Deux filtres sortent du rang, dont un proposé dans cette thèse. / In this CIFRE thesis, a collaboration between the Center of Mathematics and their Applications, École Normale Supérieure de Cachan and the company DxO, we tackle the problem of the additive decomposition of an image into base and detail. Such a decomposition is a fundamental tool in image processing. For applications to professional photo editing in DxO Photolab, a core requirement is the absence of artifacts. For instance, in the context of contrast enhancement, in which the base is reduced and the detail increased, minor artifacts becomes highly visible. The distortions thus introduced are unacceptable from the point of view of a photographer.The objective of this thesis is to single out and study the most suitable filters to perform this task, to improve the best ones and to define new ones. This requires a rigorous measure of the quality of the base plus detail decomposition. We examine two classic artifacts (halo and staircasing) and discover three more sorts that are equally crucial: contrast halo, compartmentalization, and the dark halo. This leads us to construct five adapted patterns to measure these artifacts. We end up ranking the optimal filters based on these measurements, and arrive at a clear decision about the best filters. Two filters stand out, including one we propose. Décomposition en base et détail Lissage avec préservation des contours Filtre bilatéral Mesures objectives de qualité Mappage de tons Rehaussement de contraste Base and detail decomposition Edge-aware smoothing Bilateral filtering Objective quality assessment Tone-mapping Contrast enhancement
45	Tone-mapping HDR obrazů / HDR Tone-Mapping Vančura, Jan January 2010 (has links) This thesis concerns with the introduction to the problematics of images with high dynamic range (HDR) and possibilities of HDR images compression options for display on devices with a low dynamic range (LDR). In the introduction is described historical evolution of recording of reality. It is focusing towards point of view of physics, human visual perception and digital recording. There are described the ways of generating and holding of HDR images. The thesis is corncerned to the techniques of HDR compression, it means the tone-mapping. The different techniques of tone-mapping are explained and specific aproach is targeted to the gradient domain high dynamic range compresion.
46	A Physically Based Pipeline for Real-Time Simulation and Rendering of Realistic Fire and Smoke / En fysiskt baserad rörledning för realtidssimulering och rendering av realistisk eld och rök He, Yiyang January 2018 (has links) With the rapidly growing computational power of modern computers, physically based rendering has found its way into real world applications. Real-time simulations and renderings of fire and smoke had become one major research interest in modern video game industry, and will continue being one important research direction in computer graphics. To visually recreate realistic dynamic fire and smoke is a complicated problem. Furthermore, to solve the problem requires knowledge from various areas, ranged from computer graphics and image processing to computational physics and chemistry. Even though most of the areas are well-studied separately, when combined, new challenges will emerge. This thesis focuses on three aspects of the problem, dynamic, real-time and realism, to propose a solution in form of a GPGPU pipeline, along with its implementation. Three main areas with application in the problem are discussed in detail: fluid simulation, volumetric radiance estimation and volumetric rendering. The weights are laid upon the first two areas. The results are evaluated around the three aspects, with graphical demonstrations and performance measurements. Uniform grids are used with Finite Difference (FD) discretization scheme to simplify the computation. FD schemes are easy to implement in parallel, especially with ComputeShader, which is well supported in Unity engine. The whole implementation can easily be integrated into any real-world applications in Unity or other game engines that support DirectX 11 or higher. Visualization Physically Based Pipeline Real-Time Dynamic Simulation Combustion Fire Explosion Smoke Thick Smoke Computer Graphics PDE Numerical Methods Grid Based Navier-Stokes Equation Imcompressible Fluid Radiative Transfer Equation RTE Volumetric Illumination Volumetric Rendering Volumetric Global Illumination Distant Light Source Volumetric Global Shadow Local Shadow Approximation Black-body Radiation Poisson Solver Spectroscopy Fire Color Color Reproduction Tone Mapping Color Temperature Color Matching Function Tristimulus CIE Standard Observer Color Space XYZ RGB GPU GPGPU ComputeShader DirectX 12 Unity C# Computer Sciences Datavetenskap (datalogi)

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