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Many mathematical models have been designed to remove noise from images. Most of them focus on grey value images with additive artificial noise. Only very few specifically target natural color photos taken by a digital camera with real noise. Noise in natural color photos have special characteristics that are substantially different from those that have been added artificially. In this thesis previous denoising models are reviewed. We analyze the strengths and weakness of existing denoising models by showing where they perform well and where they don't. We put special focus on two models: The steering kernel regression model and the non-local model. For Kernel Regression model, an adaptive bilateral filter is introduced as complementary to enhance it. Also a non-local bilateral filter is proposed as an application of the idea of non-local means filter. Then the idea of cross-channel denoising is proposed in this thesis. It is effective in denoising monochromatic images by understanding the characteristics of digital noise in natural color images. A non-traditional color space is also introduced specifically for this purpose. The cross-channel paradigm can be applied to most of the exisiting models to greatly improve their performance for denoising natural color images.

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Grayscale pictures were never replaced by color ones and will probably never be, because they are indispensable in many areas. In this thesis was chosen three methods for color-to-gray conversion. These methods was implemented afterwards. Within this thesis was also made test set of 24 HDR pictures, which was together with existing set of 24 LDR pictures used to test and evaluate features of implemented methods. These methods were also compared from the point of accurancy and preference using questionnaire.

Indiana University-Purdue University Indianapolis (IUPUI) / In this thesis, we describe a different implementation for in loop filtering method for 3D-HEVC. First we propose the use of adaptive loop filtering (ALF) technique for 3D-HEVC standard in-loop filtering. This filter uses Wiener–based method to minimize the Mean Squared Error between filtered pixel and original pixels. The performance of adaptive loop filter in picture based level is evaluated. Results show up to of 0.2 dB PSNR improvement in Luminance component for the texture and 2.1 dB for the depth. In addition, we obtain up to 0.1 dB improvement in Chrominance component for the texture view after applying this filter in picture based filtering. Moreover, a design of an in-loop filtering with Fast Bilateral Filter for 3D-HEVC standard is proposed. Bilateral filter is a filter that smoothes an image while preserving strong edges and it can remove the artifacts in an image. Performance of the bilateral filter in picture based level for 3D-HEVC is evaluated. Test model HTM- 6.2 is used to demonstrate the results. Results show up to of 20 percent of reduction in processing time of 3D-HEVC with less than affecting PSNR of the encoded 3D video using Fast Bilateral Filter.

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In the early days of computer graphics, research was mainly driven by the goal to create realistic synthetic imagery. By contrast, non-photorealistic computer graphics, established as its own branch of computer graphics in the early 1990s, is mainly motivated by concepts and principles found in traditional art forms, such as painting, illustration, and graphic design, and it investigates concepts and techniques that abstract from reality using expressive, stylized, or illustrative rendering techniques. This thesis focuses on the artistic stylization of two-dimensional content and presents several novel automatic techniques for the creation of simplified stylistic illustrations from color images, video, and 3D renderings. Primary innovation of these novel techniques is that they utilize the smooth structure tensor as a simple and efficient way to obtain information about the local structure of an image. More specifically, this thesis contributes to knowledge in this field in the following ways. First, a comprehensive review of the structure tensor is provided. In particular, different methods for integrating the minor eigenvector field of the smoothed structure tensor are developed, and the superiority of the smoothed structure tensor over the popular edge tangent flow is demonstrated. Second, separable implementations of the popular bilateral and difference of Gaussians filters that adapt to the local structure are presented. These filters avoid artifacts while being computationally highly efficient. Taken together, both provide an effective way to create a cartoon-style effect. Third, a generalization of the Kuwahara filter is presented that avoids artifacts by adapting the shape, scale, and orientation of the filter to the local structure. This causes directional image features to be better preserved and emphasized, resulting in overall sharper edges and a more feature-abiding painterly effect. In addition to the single-scale variant, a multi-scale variant is presented, which is capable of performing a highly aggressive abstraction. Fourth, a technique that builds upon the idea of combining flow-guided smoothing with shock filtering is presented, allowing for an aggressive exaggeration and an emphasis of directional image features. All presented techniques are suitable for temporally coherent per-frame filtering of video or dynamic 3D renderings, without requiring expensive extra processing, such as optical flow. Moreover, they can be efficiently implemented to process content in real-time on a GPU. / In den Anfängen der Computergrafik war die Forschung hauptsächlich von dem Anspruch getragen, realistisch aussehende synthetische Bilder zu erstellen. Im Gegensatz dazu ist die nicht-photorealistische Computergraphik, ein Untergebiet der Computergrafik, welches in den frühen 1990er Jahren gegründet wurde, vor allem motiviert durch Konzepte und Prinzipien der traditionellen Kunst wie Malerei, Illustration und Grafikdesign. Diese Arbeit beschäftigt sich mit der künstlerischen Verarbeitung von zweidimensionalen Bildinhalten und präsentiert mehrere neue automatische Verfahren für die Erstellung von vereinfachten künstlerischen Darstellungen von Farbbildern, Videos und 3D- Renderings. Wichtigste Neuerung dieser Techniken ist die Verwendung des Strukturtensors als eine einfache und effiziente Möglichkeit, Informationen über die lokale Struktur eines Bildes zu erhalten. Konkret werden die folgenden Beiträge gemacht. Erstens wird eine umfassende übersicht über den Strukturtensor gegeben. Insbesondere werden verschiedene Methoden für die Integration des kleineren Eigenvektorfeldes des geglätteten Strukturtensors entwickelt, und die Überlegenheit des geglätteten Strukturtensors gegenüber dem populären Edge-Tangent-Flow demonstriert. Zweitens werden separable Implementierungen des bilateralen Filters und des Difference of Gaussians Filters vorgestellt. Durch die Anpassung der Filter an die lokale Struktur des Bildes werden Bildfehler vermieden, wobei der Vorgang rechnerisch effizient bleibt. Zusammengenommen bieten beide Techniken eine effektive Möglichkeit, um einen Cartoon-ähnlichen Effekt zu erzielen. Drittens wird eine Verallgemeinerung des Kuwahara-Filters vorgestellt. Durch die Anpassung von Form, Umfang und Orientierung der Filter an die lokale Struktur werden Bildfehler verhindert. Außerdem werden direktionale Bildmerkmale besser berücksichtigt und betont, was zu schärferen Kanten und einem malerischen Effekt führt. Neben der single-scale Variante wird auch eine multi-scale Variante vorgestellt, welche im Stande ist, eine höhere Abstraktion zu erzielen. Viertens wird eine Technik vorgestellt, die auf der Kombination von flussgesteuerter Glättung und Schock-Filterung beruht, was zu einer intensiven Verstärkung und Betonung der direktionalen Bildmerkmale führt. Alle vorgestellten Techniken erlauben die zeitlich kohärente Verarbeitung von Einzelbildern eines Videos oder einer dynamischen 3D-Szene, ohne dass andere aufwendige Verfahren wie zum Beispiel die Berechnung des optischen Flusses, benötigt werden. Darüberhinaus können die Techniken effizient implementiert werden und ermöglichen die Verarbeitung in Echtzeit auf einem Grafikprozessor (GPU).

影像中的文字訊息，通常包含著與場景內容相關的重要資訊，如地點、名稱、指示、警告等，因此如何有效地在影像中擷取文字區塊，進而解讀其意義，成為近來電腦視覺領域中相當受矚目的議題。然而在眾多的場景文字偵測方法裡，絕大多數是以英文為偵測目標語言，中文方面的研究相當稀少，而且辨識率遠不及英文。因此，本論文提出以中文和英文為偵測目標語言的方法，分成以下四個主要程序：一、前處理，利用雙邊濾波器(Bilateral filter)使文字區域更加穩定；二、候選文字資訊擷取，考慮文字特徵，選用Canny 邊緣偵測和最大穩定極值區域(Maximally Stable Extremal Region)，分別提取文字邊緣和區域特徵，並結合兩者來優化擷取的資訊；三、文字連結，依中文字結構和直式、橫式兩種書寫方向，設置幾何條件連結候選文字字串；四、候選字串分類，以SVM加入影像中文字的特徵，分類文字字串和非文字字串。使得此方法可以偵測中文和英文兩種語言，並且達到不錯的辨識效果。 / Text messages in an image usually contain useful information related to the scene, such as location, name, direction and warning. As such, robust and efficient scene text detection has gained increasing attention in the area of computer vision recently. However, most existing scene text detection methods are devised to process Latin-based languages. For the few researches that reported the investigation of Chinese text, the detection rate was inferior to the result for English. In this thesis, we propose a multilingual scene text detection algorithm for both Chinese and English. The method comprises of four stages: 1. Preprocessing by bilateral filter to make the text region more stable. 2. Extracting candidate text edge and region using Canny edge detector and Maximally Stable Extremal Region (MSER) respectively. Then combine these two features to achieve more robust results. 3. Linking candidate characters: considering both horizontal and vertical direction, character candidates are clustered into text candidates by using geometrical constraints. 4. Classifying candidate texts using support vector machine (SVM), the text and non-text areas are separated. Experimental results show that the proposed method detects both Chinese and English texts, and achieve satisfactory performance compared to those approaches designed only for English detection.

This thesis focuses on the high dynamic range (HDR) imaging problematic. It describes process of capturing and storage of HDR images in brief. Main part of thesis deals with techniques of how to display HDR images on common visual display devices, which are not able to represent them directly. This process is called tone-mapping. It is firstly described in general and than the text focuses on several techniques of tone-mapping, mainly on tone-mapping using bilateral filtering.