High dynamic range video merging, tone mapping, and real-time implementation

Although High Dynamic Range (High Dynamic Range (HDR)) imaging has been the subject of significant research over the past fifteen years, the goal of cinemaquality HDR video has not yet been achieved. This work references an optical method patented by Contrast Optical which is used to capture sequences of Low Dynamic Range (LDR) images that can be used to form HDR images as the basis for HDR video. Because of the large diverence in exposure spacing of the LDR images captured by this camera, present methods of merging LDR images are insufficient to produce cinema quality HDR images and video without significant visible artifacts. Thus the focus of the research presented is two fold. The first contribution is a new method of combining LDR images with exposure differences of greater than 3 stops into an HDR image. The second contribution is a method of tone mapping HDR video which solves potential problems of HDR video flicker and automated parameter control of the tone mapping operator. A prototype of this HDR video capture technique along with the combining and tone mapping algorithms have been implemented in a high-definition HDR-video system. Additionally, Field Programmable Gate Array (FPGA) hardware implementation details are given to support real time HDR video. Still frames from the acquired HDR video system which have been merged used the merging and tone mapping techniques will be presented

Reconsidering light transport : acquisition and display of real-world reflectance and geometry

In this thesis, we cover three scenarios that violate common simplifying assumptions about the nature of light transport. We begin with the first ingredient to any çD rendering: a geometry model. Most çD scanners require the object-of-interest to show diffuse refectance. The further a material deviates from the Lambertian model, the more likely these setups are to produce corrupted results. By placing a traditional laser scanning setup in a participating (in particular, fuorescent) medium, we have built a light sheet scanner that delivers robust results for a wide range of materials, including glass. Further investigating the phenomenon of fluorescence, we notice that, despite its ubiquity, it has received moderate attention in computer graphics. In particular, to date no datadriven reflectance models of fluorescent materials have been available. To describe the wavelength-shifling reflectance of fluorescent materials, we define the bispectral bidirectional reflectance and reradiation distribution function (BRRDF), for which we introduce an image-based measurement setup as well as an efficient acquisition scheme. Finally, we envision a computer display that showsmaterials instead of colours, and present a prototypical device that can exhibit anisotropic reflectance distributions similar to common models in computer graphics.In der Computergraphik und Computervision ist es unerlässlich, vereinfachende Annahmen über die Ausbreitung von Licht zumachen. In dieser Dissertation stellen wir drei Fälle vor, in denen diese nicht zutreffen. So wird die dreidimensionale Geometrie von Gegenständen oft mit Hilfe von Laserscannern vermessen und dabei davon ausgegangen, dass ihre Oberfläche diffus reflektiert. Dies ist bei den meisten Materialien jedoch nicht gegeben, so dass die Ergebnisse oft fehlerhaft sind. Indem wir das Objekt in einem fluoreszierenden Medium einbetten, kann ein klassischer CD-Scanner-Aufbau so modifiziert werden, dass er verlässliche Geometriedaten für Objekte aus verschiedensten Materialien liefert, einschließlich Glas. Auch die akkurate Nachbildung des Aussehens von Materialien ist wichtig für die photorealistische Bildsynthese. Wieder interessieren wir uns für Fluoreszenz, diesmal allerdings für ihr charakteristisches Erscheinungsbild, das in der Computergraphik bislang kaum Beachtung gefunden hat. Wir stellen einen bildbasierten Aufbau vor, mit dem die winkel- und wellenlängenabhängige Reflektanz fluoreszierender Oberflächen ausgemessen werden kann, und eine Strategie, um solche Messungen effizient abzuwickeln. Schließlich befassen wir uns mit der Idee, nicht nur Farben dynamisch anzuzeigen, sondern auch Materialien und ihr je nach Lichteinfall und Blickwinkel unterschiedliches Aussehen. Einer generellen Beschreibung des Problems folgt die konkrete Umsetzung in Formzweier Prototypen, die verschiedene Reflektanzverteilungen auf einer Oberfläche darstellen können

Demosaicing by smoothing along 1D features

Most digital cameras capture color pictures in the form of an image mosaic, recording only one color channel at each pixel position. Therefore, an interpolation algorithm needs to be applied to reconstruct the missing color information. In this paper we present a novel Bayer pattern demosaicing approach, employing stochastic global optimization performed on a pixel neighborhood. We are minimizing a newly developed cost function that increases smoothness along one-dimensional image features. While previous algorithms have been developed focusing on LDR images only, our optimization scheme and the underlying cost function are designed to handle both LDR and HDR images, creating less demosaicing artifacts, compared to previous approaches. 1

Demosaicing by Smoothing along 1D Features

Most digital cameras capture color pictures in the form of an image mosaic, recording only one color channel at each pixel position. Therefore, an interpolation algorithm needs to be applied to reconstruct the missing color information. In this paper we present a novel Bayer pattern demosaicing approach, employing stochastic global optimization performed on a pixel neighborhood. We are minimizing a newly developed cost function that increases smoothness along one-dimensional image features. While previous algorithms have been developed focusing on LDR images only, our optimization scheme and the underlying cost function are designed to handle both LDR and HDR images, creating less demosaicing artifacts, compared to previous approaches