A method for identifying colors in urban environments using a digital camera was established. Color analysis of images was performed using the CIELAB color space. The color coordinates were used to produce a color chart of prevailing colors in the area, which was later used to design a textile pattern. Color samples were in good agreement with the perceived colors of the surroundings. Neutral colors in gray tones predominate in the majority of the city of Ljubljana, Slovenia; nevertheless, there are also bright colors, notably green, yellow, and beige. The method described is fast and reliable enough to identify colors in urban environments. However, the analysis of a large number of photographs is needed to ensure objective results. To obtain reliable results for measured color values, it is necessary to exactly define the conditions under which photographs were taken . 2011 Society for Imaging Science and Technology.

This article presents a robust translation, rotation, and scaling invariant pattern recognition algorithm using partially distorted two-dimensional (2D) contours. Both global and local matching accuracies are guaranteed: the former is achieved by using global control point (GCP) and curvature matching and the latter by using the iterative closest point (ICP) algorithm. In the proposed algorithm, an input contour is considered two possible types: first the contour contains GCP and the second contains no GCP. For the contours with no detected GCPs, the algorithm considers the contour as the second type of contour and the curvature matching algorithm is directly applied. For the contour with GCPs, a global alignment is performed using the GCPs and then, the curvature matching algorithm is applied. The validity of the algorithm is illustrated by the presentation of experimental results. The experiments show that the algorithm works well for partial object recognition with and without GCPs.

In optical imaging systems, the wavelength-dependency of the refraction indices of lenses causes chromatic aberrations: electromagnetic radiation from an object point is dispersed in a rainbow-like manner on the sensor. These aberrations were so far only measured and modeled for up to three, often relatively wideband wavelength bands, such as R, G, and B. Moreover, no relation between the aberrations of these color channels was generally considered. The authors describe here the measurement of chromatic aberrations for multiple narrowband color channels in multispectral imaging. Existing models for transversal distortions are discussed and the wavelengthdependency of their parameters is analyzed. The models are extended with univariate wavelength-dependent polynomials, thus leading to bivariate models for both space and wavelengthdependency. The authors compare the models and confirm their validity qualitatively and quantitatively and simulate aberrations with state-of-the-art raytracing software. With their wavelength-dependent model, the distortions can be compensated even at wavelengths for which no measurements are available.

This article presents a new methodology for the color accuracy optimization of a two-dimensional digital reproduction. Selecting a training set referring to the colorimetric content of the object to be reproduced results in a significant improvement of the color accuracy of an RGB reproduction. Some authors have developed methodologies for color accuracy optimization that involve the creation of specific custom-made reference targets. The methodology presented here does not involve the creation of custom-made targets, as the reference colors are selected directly on the object. In fact, a clusterization is performed on the RGB image of the object and a set of representative colors is achieved. For each RGB representative color, the corresponding CIELAB value is measured and a training set is obtained that can be used to define a transformation that maps all RGB values into CIELAB values. The experiments conducted show that using this methodology considerably improves color accuracy.

. This study examined how the display quality of liquid crystal display (LCD) devices is assessed. A subjective experiment was conducted to identify the factors involved in quality assessments and then to determine their respective contributions to these assessments. The results are expected to drive the development of an objective quality metric dedicated to color reproduction. The subjective data were analyzed by means of a multivariate analysis of variance and a correlation study. The results showed the main effect of display on all the factors that were investigated, namely, hue, contrast, saturation, naturalness, quality, and texture. Finally, among these perceptual features, contrast and hue have been demonstrated to be the most influential on the overall quality of a displayed image.

This paper aims to improve tone consistency for color electrophotography (EP). Color accuracy is crucial for printing. Calibrations are performed in EP printers to maintain consistent tone reproduction curves (TRCs). The calibration performance directly impacts the quality of color rendering. In this study, a model-based calibration approach is proposed to stabilize the TRCs. Regression models are developed to predict the primary color TRCs based on operating conditions and/or on-board sensor measurements. During a calibration, TRCs are predicted by the regression models, and the deviation is compensated by adjusting EP control parameters and modifying the tone correction mapping. The effectiveness of the proposed approach is validated using an off-the-shelf in-line four color EP printer under various environmental conditions and consumable factors. The experimental results demonstrate a 63.3% reduction in root-mean-squared error over the existing calibration method.

The MetallicArt technique is used as a visual security feature to hide patterns in CMY images using an additional silver ink. The patterns are hidden under nonspecular viewing conditions and visible under specular viewing conditions. By varying the amount of silver ink, the authors control the intensity of the specular reflection of the printed pattern. Using a spectral reflection prediction model, they can constrain the maximization of the silver ink (S) in order to keep the color difference between the original CMY color and the fitted CMYS color under a given threshold, ensuring that the pattern is hidden under nonspecular viewing conditions. When the printing device requires the inks to be UV cured, the leafing effect of the silver ink is reduced. This also reduces the specular reflection of the silver ink, which becomes comparable to the specular reflection of the yellow ink. Since both specular reflections are similar, it is difficult to distinguish the embedded patterns under specular viewing conditions when both inks are present. The authors, therefore, propose a new algorithm to embed patterns in CMY images that not only maximizes silver but also minimizes yellow. Experimental results show that the proposed algorithm enhances the visibility of the patterns under specular viewing conditions, allowing the use of MetallicArt when the printing device requires UV curing.

Ever since 1898, when Pia took the first photographs of the Turin Shroud, many researchers have advanced hypotheses to account for the body image visible on the most important Relic of Christianity. Until now, many interesting hypotheses have been examined, but none of them can completely explain the mysterious image. This article considers the most important of these hypotheses and concludes that radiation was responsible for the formation of the image. Although this hypothesis is still incomplete, of the various sources of radiation phenomena, corona discharge is preferred.