Pixel Arrangement and Mapping Algorithm for Improving Saturation and Brightness

With the increasing demand for display effects and resolution in the display market, the traditional RGBW permutation has defects such as reduced display saturation and poor image restoration. A new sub-pixel arrangement is designed for these defects, reducing the number of white pixels W and adding yellow pixels Y, which reduces the influence of white pixels on surrounding pixels compared to the conventional RGBW structure. According to the new arrangement method, two new mapping algorithms are designed, and the saturation concept is introduced. The yellow component and the white component are adjusted by the saturation change to effectively improve the image saturation. The simulation shows that the new mapping algorithm (1) has a higher degree of restoration on the image and increases the saturation by 10%. The new mapping algorithm (2) can improve the brightness based on maintaining the high saturation of the original image

Evaluation of the color image and video processing chain and visual quality management for consumer systems

With the advent of novel digital display technologies, color processing is increasingly becoming a key aspect in consumer video applications. Today’s state-of-the-art displays require sophisticated color and image reproduction techniques in order to achieve larger screen size, higher luminance and higher resolution than ever before. However, from color science perspective, there are clearly opportunities for improvement in the color reproduction capabilities of various emerging and conventional display technologies. This research seeks to identify potential areas for improvement in color processing in a video processing chain. As part of this research, various processes involved in a typical video processing chain in consumer video applications were reviewed. Several published color and contrast enhancement algorithms were evaluated, and a novel algorithm was developed to enhance color and contrast in images and videos in an effective and coordinated manner. Further, a psychophysical technique was developed and implemented for performing visual evaluation of color image and consumer video quality. Based on the performance analysis and visual experiments involving various algorithms, guidelines were proposed for the development of an effective color and contrast enhancement method for images and video applications. It is hoped that the knowledge gained from this research will help build a better understanding of color processing and color quality management methods in consumer video

Experimental Evaluation and Analysis of LED Illumination Source for Endoscopy Imaging

The minimally invasive surgery uses a small instrument with camera and light to fit the tiny cut in the skin. The selection of the light depends on the power and driving current of the circuit. It can also help in the standardization of the camera and capture the tissues' true-colour image. This paper presents the LED source analysis used in the clinical endoscopes for surgery and the human body's medical examination. Initially, a LED source selection mechanism generating intense illuminance in a visible band is proposed. A low-cost prototype model is developed to analyze the wavelength and illuminance of three different LEDs types. An effect on variation in LED illumination is investigated by changing the distance between the Borescope and LED source. True-colour image generation and tissue contrast are more important in medical diagnostics. Therefore, a sigmoid function improving the whole contrast ratio of the captured image in real-time is presented. The results of spectrum and wavelength for a current variation are presented. Type 3 LED produces higher illumination (i.e., 395 Klux) and peak wavelength (i.e., 622.05 nm) than other LEDs, while type-2 LED has better FWHM for the blue colour spectrum. The modification in the sigmoid function enhances the image with 34.25 peak PSNR producing a true-colour image

High Dynamic Range (HDR) Display Perception

Displays have undergone a huge development in the last several decades. From cathode-ray tube (CRT), liquid crystal display (LCD), to organic light-emitting diode (OLED), even Q-OLED, the new configurations of the display bring more and more functions into industry and daily life. In the recent several years, high dynamic range (HDR) displays become popular. HDR displays usually refer to that the black level of the display is darker and the peak being brighter compared with the standard dynamic range (SDR) display. Traditionally, the peak luminance level can be used as the white in characterization and calibration. However, for HDR displays, the peak luminance is higher than the traditional diffuse white level. Exploration of the perceptual diffuse white in HDR image when presented in displays is proposed, which can be beneficial to the characterizing and the optimizing the usage of the HDR display. Moreover, in addition to the ``diffuse white , 3D color gamut volume can be calculated in some specific color appearance models. Calculation and modeling of the 3D color gamut volume can be very useful for display design and better characterizing display color reproduction capability. Furthermore, the perceptional color gamut volume can be measured through psychophysical experiments. Comparison between the perceptional color gamut volume and the theoretical 3D gamut volume calculations will reveal some insights for optimizing the usage of HDR displays. Another advantage of the HDR display is its darker black compared with the SDR display. Compared with the real black object, what level of black is `perfect\u27 enough in displays? Experiments were proposed and conducted to evaluate that if the HDR display is capable of showing ``perfect black for different types of background images/patterns. A glare-based model was proposed to predict the visual ``perfect black. Additionally, the dynamic range of human vision system is very large. However, the simultaneous dynamic range of human vision system is much smaller and is important for the fine tuning usage of HDR displays. The simultaneous dynamic range was measured directly for different stimulus sizes. Also, it was found that the simultaneous dynamic range was peak luminance level dependent. A mathematical model was proposed based on the experimental data to predict the simultaneous dynamic range. Also the spatial frequency effect of the target pattern on the simultaneous dynamic range was measured and modeled. The four different assessments about HDR displays perception would provide experimental data and models for a better understanding of HDR perception and tuning of the HDR display

Artistic Path Space Editing of Physically Based Light Transport

Die Erzeugung realistischer Bilder ist ein wichtiges Ziel der Computergrafik, mit Anwendungen u.a. in der Spielfilmindustrie, Architektur und Medizin. Die physikalisch basierte Bildsynthese, welche in letzter Zeit anwendungsübergreifend weiten Anklang findet, bedient sich der numerischen Simulation des Lichttransports entlang durch die geometrische Optik vorgegebener Ausbreitungspfade; ein Modell, welches für übliche Szenen ausreicht, Photorealismus zu erzielen. Insgesamt gesehen ist heute das computergestützte Verfassen von Bildern und Animationen mit wohlgestalteter und theoretisch fundierter Schattierung stark vereinfacht. Allerdings ist bei der praktischen Umsetzung auch die Rücksichtnahme auf Details wie die Struktur des Ausgabegeräts wichtig und z.B. das Teilproblem der effizienten physikalisch basierten Bildsynthese in partizipierenden Medien ist noch weit davon entfernt, als gelöst zu gelten. Weiterhin ist die Bildsynthese als Teil eines weiteren Kontextes zu sehen: der effektiven Kommunikation von Ideen und Informationen. Seien es nun Form und Funktion eines Gebäudes, die medizinische Visualisierung einer Computertomografie oder aber die Stimmung einer Filmsequenz -- Botschaften in Form digitaler Bilder sind heutzutage omnipräsent. Leider hat die Verbreitung der -- auf Simulation ausgelegten -- Methodik der physikalisch basierten Bildsynthese generell zu einem Verlust intuitiver, feingestalteter und lokaler künstlerischer Kontrolle des finalen Bildinhalts geführt, welche in vorherigen, weniger strikten Paradigmen vorhanden war. Die Beiträge dieser Dissertation decken unterschiedliche Aspekte der Bildsynthese ab. Dies sind zunächst einmal die grundlegende Subpixel-Bildsynthese sowie effiziente Bildsyntheseverfahren für partizipierende Medien. Im Mittelpunkt der Arbeit stehen jedoch Ansätze zum effektiven visuellen Verständnis der Lichtausbreitung, die eine lokale künstlerische Einflussnahme ermöglichen und gleichzeitig auf globaler Ebene konsistente und glaubwürdige Ergebnisse erzielen. Hierbei ist die Kernidee, Visualisierung und Bearbeitung des Lichts direkt im alle möglichen Lichtpfade einschließenden "Pfadraum" durchzuführen. Dies steht im Gegensatz zu Verfahren nach Stand der Forschung, die entweder im Bildraum arbeiten oder auf bestimmte, isolierte Beleuchtungseffekte wie perfekte Spiegelungen, Schatten oder Kaustiken zugeschnitten sind. Die Erprobung der vorgestellten Verfahren hat gezeigt, dass mit ihnen real existierende Probleme der Bilderzeugung für Filmproduktionen gelöst werden können

Optimal Depth Estimation and Extended Depth of Field from Single Images by Computational Imaging using Chromatic Aberrations

The thesis presents a thorough analysis of a computational imaging approach to estimate the optimal depth, and the extended depth of field from a single image using axial chromatic aberrations. To assist a camera design process, a digital camera simulator is developed which can efficiently simulate different kind of lenses for a 3D scene. The main contribution in the simulator is the fast implementation of space variant filtering and accurate simulation of optical blur at occlusion boundaries. The simulator also includes sensor modeling and digital post processing to facilitate a co-design of optics and digital processing algorithms. To estimate the depth from color images, which are defocused to different amount due to axial chromatic aberrations, a low cost algorithm is developed. Due to varying contrast across colors, a local contrast independent blur measure is proposed. The normalized ratios between the blur measure of all three colors (red, green and blue) are used to estimate the depth for a larger distance range. The analysis of depth errors is performed, which shows the limitations of depth from chromatic aberrations, especially for narrowband object spectra. Since the blur changes over the field and hence depth, therefore, a simple calibration procedure is developed to correct the field varying behavior of estimated depth. A prototype lens is designed with optimal amount of axial chromatic aberrations for a focal length of 4 mm and F-number 2.4. The real captured and synthetic images show the depth measurement with the root mean square error of 10% in the distance range of 30 cm to 2 m. Taking the advantage of chromatic aberrations and estimated depth, a method is proposed to extend the depth of field of the captured image. An imaging sensor with white (W) pixel along with red, green and blue (RGB) pixels with a lens exhibiting axial chromatic aberrations is used to overcome the limitations of previous methods. The proposed method first restores the white image with depth invariant point spread function, and then transfers the sharpness information of the sharpest color or white image to blurred colors. Due to broadband color filter responses, the blur of each RGB color at its focus position is larger in case of chromatic aberrations as compared to chromatic aberrations corrected lens. Therefore, restored white image helps in getting a sharper image for these positions, and also for the objects where the sharpest color information is missing. An efficient implementation of the proposed algorithm achieves better image quality with low computational complexity. Finally, the performance of the depth estimation and extended depth of field is studied for different camera parameters. The criteria are defined to select optimal lens and sensor parameters to acquire desired results with the proposed digital post processing algorithms