Evaluation and optimal design of spectral sensitivities for digital color imaging

The quality of an image captured by color imaging system primarily depends on three factors: sensor spectral sensitivity, illumination and scene. While illumination is very important to be known, the sensitivity characteristics is critical to the success of imaging applications, and is necessary to be optimally designed under practical constraints. The ultimate image quality is judged subjectively by human visual system. This dissertation addresses the evaluation and optimal design of spectral sensitivity functions for digital color imaging devices. Color imaging fundamentals and device characterization are discussed in the first place. For the evaluation of spectral sensitivity functions, this dissertation concentrates on the consideration of imaging noise characteristics. Both signal-independent and signal-dependent noises form an imaging noise model and noises will be propagated while signal is processed. A new colorimetric quality metric, unified measure of goodness (UMG), which addresses color accuracy and noise performance simultaneously, is introduced and compared with other available quality metrics. Through comparison, UMG is designated as a primary evaluation metric. On the optimal design of spectral sensitivity functions, three generic approaches, optimization through enumeration evaluation, optimization of parameterized functions, and optimization of additional channel, are analyzed in the case of the filter fabrication process is unknown. Otherwise a hierarchical design approach is introduced, which emphasizes the use of the primary metric but the initial optimization results are refined through the application of multiple secondary metrics. Finally the validity of UMG as a primary metric and the hierarchical approach are experimentally tested and verified

Analysis of image noise in multispectral color acquisition

The design of a system for multispectral image capture will be influenced by the imaging application, such as image archiving, vision research, illuminant modification or improved (trichromatic) color reproduction. A key aspect of the system performance is the effect of noise, or error, when acquiring multiple color image records and processing of the data. This research provides an analysis that allows the prediction of the image-noise characteristics of systems for the capture of multispectral images. The effects of both detector noise and image processing quantization on the color information are considered, as is the correlation between the errors in the component signals. The above multivariate error-propagation analysis is then applied to an actual prototype system. Sources of image noise in both digital camera and image processing are related to colorimetric errors. Recommendations for detector characteristics and image processing for future systems are then discussed

Print engine color management using customer image content

The production of quality color prints requires that color accuracy and reproducibility be maintained to within very tight tolerances when transferred to different media. Variations in the printing process commonly produce color shifts that result in poor color reproduction. The primary function of a color management system is maintaining color quality and consistency. Currently these systems are tuned in the factory by printing a large set of test color patches, measuring them, and making necessary adjustments. This time-consuming procedure should be repeated as needed once the printer leaves the factory. In this work, a color management system that compensates for print color shifts in real-time using feedback from an in-line full-width sensor is proposed. Instead of printing test patches, this novel attempt at color management utilizes the output pixels already rendered in production pages, for a continuous printer characterization. The printed pages are scanned in-line and the results are utilized to update the process by which colorimetric image content is translated into engine specific color separations (e.g. CIELAB-\u3eCMYK). The proposed system provides a means to perform automatic printer characterization, by simply printing a set of images that cover the gamut of the printer. Moreover, all of the color conversion features currently utilized in production systems (such as Gray Component Replacement, Gamut Mapping, and Color Smoothing) can be achieved with the proposed system

DigitalBeing: an Ambient Intelligent Dance Space.

DigitalBeing is an ambient intelligent system that aims to use stage lighting and lighting in projected imagery within a dance performance to portray dancer’s arousal state. The dance space will be augmented with pressure sensors to track dancers’ movements; dancers will also wear physiological sensors. Sensor data will be passed to a three layered architecture. Layer 1 is composed of a system that analyzes sensor data. Layer 2 is composed of two intelligent lighting systems that use the analyzed sensor information to adapt onstage and virtual lighting to show dancer’s arousal level. Layer 3 translates lighting changes to appropriate lighting board commands as well as rendering commands to render the projected imagery

A simplified HDR image processing pipeline for digital photography

High Dynamic Range (HDR) imaging has revolutionized the digital imaging. It allows capture, storage, manipulation, and display of full dynamic range of the captured scene. As a result, it has spawned whole new possibilities for digital photography, from photorealistic to hyper-real. With all these advantages, the technique is expected to replace the conventional 8-bit Low Dynamic Range (LDR) imaging in the future. However, HDR results in an even more complex imaging pipeline including new techniques for capturing, encoding, and displaying images. The goal of this thesis is to bridge the gap between conventional imaging pipeline to the HDR’s in as simple a way as possible. We make three contributions. First we show that a simple extension of gamma encoding suffices as a representation to store HDR images. Second, gamma as a control for image contrast can be ‘optimally’ tuned on a per image basis. Lastly, we show a general tone curve, with detail preservation, suffices to tone map an image (there is only a limited need for the expensive spatially varying tone mappers). All three of our contributions are evaluated psychophysically. Together they support our general thesis that an HDR workflow, similar to that already used in photography, might be used. This said, we believe the adoption of HDR into photography is, perhaps, less difficult than it is sometimes posed to be

Caracterização física de preparações líquidas não estéreis: aparência

The present dissertation consists in the development of a visual and instrumental method for the evaluation of the color of a non-sterile liquid formulation. The color of the formulation was analyzed at different time intervals, after being subjected to different conditions of temperature and relative humidity in its pre-stability period. The evaluation occurred by comparing the formulation with different color scales reproduced based on the European Pharmacopoeia 9.7. Due to the fact that the visual assessment could be subjective, an instrumental color evaluation was performed from three- and two-dimensional color spaces, namely the CIELAB color space. Since the two-dimensional representation used to the instrumental specification of color does not consider all the attributes associated with color (does not include brightness), the CIELAB Difference (ΔE∗) between the color of the standard solutions of the scales and the formulation analyzed under different conditions was determined. The CIELAB Difference between two colors considers all the parameters that influence the color sensation and allows determining which of the standard solution has the most similar color to the formulation under analysis. Finally, using the standard solution with the most intense color of one of the scales reproduced, a rectangular color tolerance box was established to limit the acceptable tolerance for the coordinates of the formulation under analysis: all the formulations with the color coordinates outside the tolerance limits should be potentially rejected and investigated. However, the tolerance defined with the most intense color of one of the scales is merely representative: the main objective is, over time, to obtain a history of the coordinates of the color of the formulation and establish as tolerance limit the coordinates of the color associated with a formulation that is at the limit of the specifications associated with itA presente dissertação tem como objetivo o desenvolvimento e implementação de um método de avaliação da cor de uma preparação líquida não estéril analisada em diferentes intervalos de tempo, após estar sujeita a diferentes condições de temperatura e humidade relativa no seu período de pré-estabilidade. A avaliação ocorreu através da comparação entre a formulação e diferentes escalas da cor reproduzidas com base na Farmacopeia Europeia 9.7. Devido ao facto de a avaliação visual poder ser subjetiva, procedeu-se a uma avaliação instrumental da cor a partir de espaços de cor tridimensionais e bidimensionais, nomeadamente o espaço de cor CIELAB. Dado que a representação bidimensional utilizada para a especificação instrumental da cor não considera todos os atributos associados à mesma (não inclui a luminosidade), determinou-se a Diferença CIELAB (Δ"∗) entre a cor das amostras de referência das escalas e a cor da formulação em análise. A Diferença CIELAB considera todos os parâmetros que influenciam a sensação da cor e permite determinar qual das amostras de referência tem a cor mais semelhante à formulação em análise. Por fim, recorrendo à amostra de referência com a cor mais intensa de uma das escalas, estabeleceu-se uma caixa retangular de tolerância para a cor da formulação em avaliação: todas as formulações com coordenadas fora do limite da caixa devem ser rejeitadas e investigadas. No entanto, a tolerância definida com as coordenadas da cor mais intensa de uma das escalas é meramente representativa: o objetivo é, através de histórico de coordenadas da cor da formulação ao longo do tempo, estabelecer o limite de tolerância com as coordenadas associadas a uma formulação que se encontre no limite das especificações associadas à mesmaMestrado em Engenharia Químic

Gamut extension algorithm development and evaluation for the mapping of standard image content to wide-gamut displays

Wide-gamut display technology has provided an excellent opportunity to produce visually pleasing images, more so than in the past. However, through several studies, including Laird and Heynderick, 2008, it was shown that linearly mapping the standard sRGB content to the gamut boundary of a given wide-gamut display may not result in optimal results. Therefore, several algorithms were developed and evaluated for observer preference, including both linear and sigmoidal expansion algorithms, in an effort to define a single, versatile gamut expansion algorithm (GEA) that can be applied to current display technology and produce the most preferable images for observers. The outcome provided preference results from two displays, both of which resulted in large scene dependencies. However, the sigmoidal GEAs (SGEA) were competitive with the linear GEAs (LGEA), and in many cases, resulted in more pleasing reproductions. The SGEAs provide an excellent baseline, in which, with minor improvements, could be key to producing more impressive images on a wide-gamut display