Specification of cartographic layer tinting schemes for color graphic monitors

This study provides some guidelines using and comparing the RGB (red, green, blue), HSV (hue, saturation, value), and HLS (hue, lightness, saturation) color specification systems to help designers of computer produced layer tinted maps to select appropriate and effective colors from the immense palette provided by modern color monitors. Map samples from around the world were used in a color matching experiment in which screen colors matching each layer tint were displayed on a color graphic monitor. ROB color coordinates from look-up tables and CIE (Y,x,y) coordinates from spectrophotometric measurements were recorded for each color. Algorithms converted RGB coordinates to HSV and HLS color coordinates. Polynomial curve fitting was used to define continuous layer tinting schemes in terms of elevation levels and both HSV and ilLS color coordinates

Analytical methods fort he study of color in digital images

La descripció qualitativa dels colors que composen una imatge digital és una tasca molt senzilla pel sistema visual humà. Per un ordinador aquesta tasca involucra una gran quantitat de qüestions i de dades que la converteixen en una operació de gran complexitat. En aquesta tesi desenvolupam un mètode automàtic per a la construcció d’una paleta de colors d’una imatge digital, intentant respondre a les diferents qüestions que se’ns plantegen quan treballam amb colors a dins el món computacional. El desenvolupament d’aquest mètode suposa l’obtenció d’un algorisme automàtic de segmentació d’histogrames, el qual és construït en detall a la tesi i diferents aplicacions del mateix son donades. Finalment, també s’explica el funcionament de CProcess, un ‘software’ amigable desenvolupat per a la fàcil comprensió del color

Operator/equipment Performance Measures: Results Of Literature Search

Literature review focuses on topics concerning perception, acceptable transmission delay, fidelity, and visual systems, including resolution, field of view, and target-background contrast

New Test Set for Video Quality Benchmarking

A new test set design and benchmarking approach (US Patent pending) allows a standard observer to assess the end-to-end image quality characteristics of video imaging systems operating in day time or low-light conditions. It uses randomized targets based on extensive application of Photometry, Geometrical Optics, and Digital Media. The benchmarking takes into account the target’s contrast sensitivity, its color characteristics, and several aspects of human vision such as visual acuity and dynamic response. The standard observer is part of the extended video imaging system (EVIS). The new test set allows image quality benchmarking by a panel of standard observers at the same time. The new approach shows that an unbiased assessment can be guaranteed. Manufacturers, system integrators, and end users will assess end-to-end performance by simulating a choice of different colors, luminance levels, and dynamic conditions in the laboratory or in permanent video systems installations

Modelling color changes in wood during conventional drying

La coloration du bois pendant le séchage diminue la qualité et la valeur du produit fini, augmente les coûts de production et diminue le rendement matière. C’est un processus complexe qui est difficile à prédire. Le développement d'un modèle de changement de couleur du bois en cours de séchage peut donc favoriser l’économie de temps et de matière première. Deux séries de six essais ont été effectuées dans cette étude sur l’aubier du bouleau à papier et de l'érable à sucre afin de mesurer le changement de couleur du bois pendant un séchage conventionnel à trois niveaux différents de température sèche (40, 60 et 80°C) et deux niveaux de dépression au thermomètre humide (4 et 15°C). Les données de ces essais ont conduit au développement de modèles statistiques du changement de l’indice de clarté L* pour chaque espèce, séparément pour la surface et l’intérieur du bois, en utilisant des modèles de régression mixte avec la planche considérée comme effet aléatoire. Deux types de modèles ont été développés, soit en considérant les trois températures sèches (40, 60 et 80°C) d’une part, et les deux températures les plus élevées seulement (60 et 80°C) d’autre part. Finalement, les modèles statistiques furent combinés à un modèle existant de transfert de masse et de chaleur (DRYTEK) afin de simuler les changements de couleur pour tout autre programme spécifique de séchage à moyenne température. Les paramètres du modèle numérique de transfert de masse et de chaleur ont été mesurés préalablement pour les deux espèces. Les modèles statistiques et les modèles intégrés de changement de couleur furent enfin validés en réalisant pour chaque espèce un essai indépendant de séchage à une température sèche de 70°C et à une dépression au thermomètre humide de 10°C. Les résultats des essais de mesure de couleur aux températures de 60 et 80°C montrent que les valeurs de L* des deux espèces à l’intérieur de la planche diminuent rapidement avec une diminution de la teneur en humidité (M) jusqu’au point de saturation des fibres. Par la suite, les valeurs de L* diminuent lentement jusqu'à 15 - 25% M où celles-ci peuvent même commencer à augmenter. Le changement de couleur du bois à 40°C est très faible ou inexistant. Les valeurs de L* à la surface de la planche diminuent également de façon substantielle avec la diminution de la teneur en humidité, exception faite à 40°C. Pour l’ensemble de l’épaisseur du bois, plus élevée est la température de séchage, plus grande est la diminution des valeurs de L*. Réciproquement, plus forte est la dépression au thermomètre humide, plus faible est le changement de couleur à une température sèche donnée. Les composantes a* et b* montrent un comportement similaire à L* par rapport aux variations de la température de séchage et de la dépression au thermomètre humide. Par contre, les valeurs de a* et b* augmentent avec la teneur en humidité au lieu de diminuer. La comparaison des valeurs de L* obtenues des modèles statistiques de prévision avec les valeurs de L* mesurées expérimentalement à partir des essais de validation montre une très forte similarité des deux types de résultats dans le cas de l'érable de sucre. Pour le bouleau à papier, un écart important est observé entre les valeurs prédites et mesurées au-dessus du point de saturation des fibres. La relation teneur en humidité-potentiel hydrique mesurée expérimentalement montre que le potentiel hydrique augmente avec la température à une teneur en humidité donnée. Pour les deux espèces, un plateau caractéristique est observé dans la gamme de potentiels hydriques entre -2000 et -6000 J kg-1. Tel que prévu, la conductivité hydrique effective augmente avec le contenu d'humidité et la température, et elle est plus élevée en direction radiale qu’en direction tangentielle. Le coefficient de transfert convectif de masse augmente avec la température de séchage à une dépression au thermomètre humide donnée, alors qu’il diminue avec la dépression au thermomètre humide à une température de séchage donnée. Finalement, la comparaison des mesures de changement de couleur au cours des essais de validation avec les valeurs simulées à partir des modèles statistiques combinés au modèle de transfert de masse et de chaleur montre une évolution des valeurs de L* très similaire dans le cas de l’érable à sucre. À l’instar des modèles statistiques, un écart important existe entre les deux types de résultats pour le bouleau à papier dans la première partie du séchage.Wood discoloration during drying is diminishing quality and value of end product, increasing production costs and decreasing yield. Wood discoloration during drying is a complex process which is difficult to predict. The development of a wood color model can save material and time by simulating color changes for any specific drying conditions. A set of six experiments were performed in this study on paper birch and sugar maple sapwood to measure wood color changes during conventional drying at three different levels of dry-bulb temperature (40, 60 and 80˚C) and two levels of wet-bulb depression (4 and 15˚C). Statistical wood color models for lightness L* were proposed for each species, both for the wood surface and through the board thickness, to predict the wood color changes during conventional drying using mixed regression models with the board sample taken as the random effect. Three temperature (3T) (40, 60 and 80˚C) and two temperature (2T) (60 and 80˚C) models were developed. Finally, the statistical wood color models were integrated into an existing heat and mass transfer numerical model (DRYTEK) in order to simulate, for any conventional dynamic wood drying schedule, wood color changes on the surface and through the board thickness. The numerical model parameters (moisture content-water potential relationship, effective water conductivity, convective mass transfer coefficient) were experimentally determined for paper birch and sugar maple at the three drying temperatures. Both types of wood color predictive models were then validated by means of an independent drying run conducted at the dry-bulb temperature of 70°C and the wet-bulb depression of 10oC. The results of the wood color measurement tests show that at the dry-bulb temperatures of 60 and 80˚C, the L* values of both species below the surface decrease rapidly with a decrease of the moisture content (M) from the green state to the fiber saturation point. Then, the L* values decrease slowly until about 15 - 25% M where they may even start to increase. Wood color changes at 40˚C were found very small, either positive or negative. The L* values at the surface also decrease as the moisture content decreases and, except for the temperature of 40oC, the changes in color increase with the drying temperature. In general, the higher is the dry-bulb temperature, the greater is the decrease of the L* values through the board thickness. Conversely, the higher is the wet-bulb depression at a given dry-bulb temperature, the smaller are the color changes. The color components a* and b* follow a similar behavior as L* with respect to drying temperature and wet bulb depression. However, contrarily to the L* values, the a* and b* values increase with a decrease of M. The comparison of the predicted L* values obtained from the statistical models with the experimental L* values obtained from the validation tests shows a very good agreement between both types of results in the case of sugar maple. For paper birch, a fairly large discrepancy is observed during the first part of drying between predicted and experimental results but a better agreement is found at the end of drying. The results of the moisture content-water potential relationship determination show that the water potential increases with temperature at a given moisture content. A characteristic plateau was found in the water potential range of -2,000 and -6,000 J kg-1. As expected, the effective water conductivity increases with moisture content and temperature and it is higher in the radial direction than in the tangential direction. The convective mass transfer coefficient increases with dry-bulb temperature at a given wet-bulb depression, whereas it decreases with an increase of web-bulb depression at a given dry-bulb temperature. Finally, the comparison of the wood color measurements during the validation tests on paper birch and sugar maple with the wood color values simulated with the integrated statistical/numerical models shows a very good agreement between both types of results in the case of sugar maple. As it was observed for the statistical models, the fit was poorer in the case of paper birch, especially above the fiber saturation point where the initial moisture content seems to be an important factor in the color changes behavior of wood during drying

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

Advances in electrochromic materials

The development of a Microsoft® Excel® spreadsheet is described, for the accurate calculation of CIE (Commission Internationale de l’Eclairage) 1931 xy chromaticity coordinates and luminance data from visible region absorption spectra recorded in transmission mode. Using firmly established CIE principles, absorbance-wavelength data from visible spectra are taken as input, with chromaticity coordinates being generated as output. Colour stimulus measurement example calculation results are firstly presented for aqueous solutions of the dyes, Erythrosin B (red, x, y = 0.608, 0.365), Acid Green 25 (x, y = 0.086, 0.298) and Remaxol Brilliant Blue R (x, y = 0.153, 0.045), and then for tracking electrochromic in situ colour stimulus changes in the methyl viologen and di-n-heptyl viologen systems. The quantification of colour during each viologen dication to cationradical reduction process, and each reverse (oxidation) process, showed that subtle changes in both hue and luminance could be detected, with evidence of colour contributions from both the cation radical and the cation radical dimer. Ruthenium purple (RP) films on transmissive tin-doped indium oxide (ITO)/glass substrates have been synthesised by a novel electrochemical coagulation technique. Using the CIE system of colorimetry, the colour stimulus of the electrochromic RP films and the changes that take place on reversibly switching to the colourless form have been calculated from in situ visible spectra recorded under electrochemical control. (Continues...)

Chromatic filters for color vision deficiencies

Dissertação de mestrado em Optometria AvançadaAbout 10% of the population have some form of color vision deficiency. One of the most sever deficiencies is dichromacy. Dichromacy impairs color vision and impoverishes the discrimination of surface colors in natural scenes. Computational estimates based on hyperspectral imaging data from natural scenes suggest that dichromats can discriminate only about 7% of the number of colors discriminated by normal observers on natural scenes. These estimates, however, assume that the colors are equally frequent. Yet, pairs of color confused by dichromats may be rare and thus have small impact on the overall perceived chromatic diversity. By using an experimental setup that allows visual comparation between different spectra selected form hyperspectral images of natural scenes, it was estimated that the number of pairs that dichromats could discriminate was almost 70% of those discriminated by normal observers, a fraction much higher than anticipated from estimates of the number of discernible colors on natural scenes. Therefore, it may be rare for a dichromat to encounter two objects of different colors that he confounds. Thus, chromatic filters for color vision deficiencies intended to improve all colors in general may constitute low practical value. On this work it is proposed a method to compute filters specialized for a specific color-detection task, by taking into account the user’s color vision type, the local illuminant, and the reflectance spectra of the objects intended to be distinguished during that task. This method was applied on a case of a medical practitioner with protanopia to idealize a filter to improve detection of erythema on the skin of its patients. The filter improved the mean color difference between erythema and normal skin by 44%.Cerca de 10% da população possui alguma forma de deficiência de visão de cor. Uma das deficiências mais severas é a dicromacia. Dicromacia prejudica a visão das cores e empobrece a discriminação de superficies coloridas em cenas naturais. Estimativas computacionais baseadas em dados de imagens hiperespectrais de cenas naturais sugerem que dicromatas só pode discriminar cerca de 7% do número de cores discriminadas por observadores normais em cenas naturais. Estas estimativas, no entanto, assumem que todas as cores são igualmente frequentes. Contudo, pares de cores confundidos por dichromats podem ser raros e, portanto, têm pequeno impacto na diversidade cromática global percebida. Ao usar uma montagem experimental que permite comparação visual entre espectros diferentes selecionados a partir de imagens hiperespectrais de cenas naturais, estimou-se que o número de pares que dicromatas poderiam discriminar era quase 70% dos discriminados por observadores normais, uma fração muito maior do que o antecipado a partir de estimativas do número de cores percebidas em cenas naturais. Portanto, pode ser raro para um dicromat para encontrar dois objetos cujas cores ele confunda. Assim, filtros cromático para deficiências de visão das cores pretendidos para melhorar todas as cores em geral podem constituir baixo valor prático. Neste trabalho é proposto um método para calcular filtros especializados para uma tarefa específica de detecção de cor, tendo em conta o tipo de visão de cor do utilizador, o iluminante local, e os espectros de reflectancia dos objetos pretendidos a serem distinguidos durante essa tarefa. Este método foi aplicado em um caso de um médico com Protanopia para idealizar um filtro para melhorar a detecção de eritema na pele de seus pacientes. O filtro melhorou a diferença média de cor entre o eritema e a pele normal por 44%