Color Research and Application最新文献

In this work, a machine learning methodology is proposed for the issue of color space Euclidization. Given a color difference formula as reference distance law, the Euclidization task consists in finding an injective transformation from the original color space into a real vector space and the corresponding inverse transformation, such that the Euclidean distances in the embedded color space align with the reference color distances. For this, artificial neural networks are devised as function approximators for the color space transformations being sought. Training these neural networks is accomplished through unsupervised learning, making use of random sampling and gradient descent. As key disagreement measure, either the (symmetric) relative isometric disagreement or the standardized residual sum of squares (STRESS) index is considered at a time and incorporated as part of the optimization criterion into the objective function. Comparative evaluation is carried out on well-established color distance laws, including the CIELAB-based DE2000 color difference formula. The evaluation results indicate significant performance advantages of the proposed approach over previous contributions.

Hue can be described with two types of scales. The first, for hue discrimination, is of the form of a hue angle metric such as found in the Munsell and CIELAB systems. The second, for hue appearance, is in the form of a hue quadrature metric as found in the NCS system and color appearance models such as CIECAM16. Any useful hue metric should also exhibit hue constancy – the important concept that stimuli of various lightness and saturation, but identical hue designations appear to be of the same hue. Hue angle in the IPT color model has repeatedly been shown to very well describe contours of constant hue and has been rigorously tested over more than two decades. However, the IPT model was not designed with hue spacing, for either discrimination or appearance, in mind. This paper describes the derivation of a fundamental and physiologically plausible model, called FHS for Fundamental Hue Scales, with predictors for both hue discrimination and hue appearance built directly from cone fundamentals and with hue linearity as good as that found in IPT. Such a model can be used with individual LMS color matching functions as the basis for the hue dimension of improved, and individualized, color appearance scales.

The intangible cultural heritage of Yangjiabu New Year woodblock paintings (YNYWPs) has numerous potential cultural, artistic, and economic values. The quantitative color characteristics of YNYWPs, which have always been disregarded, can offer evidence in support of their inheritance and conservation. Utilizing the principles and methods of color science and spectral imaging technology, the color characteristics, including spectral characteristics, colorimetric characteristics, and color combination regularity, were quantitatively investigated by measuring and capturing the representative works. The results show that the spectral reflectances of the seven colors (i.e., red, yellow, green, cyan, violet, black, and paper color) adopted in the selected paintings have no significant structured features and can be accurately described using the first six derived eigenvectors by principal component analysis. The Xuan paper and the yellow color have higher reflectance than the other five colors. Correspondingly, their Commission Internationale de l'Eclairage (CIE) 1964 XYZ stimulus values are also relatively high. The others cover a narrow range in the CIE XYZ system. When transformed into the CIELAB color space, the seven colors can be relatively uniformly distributed in the color space. With regards to the color combination regularity, red, yellow, and cyan tend to occupy a large area in the selected paintings. In contrast, the other colors, especially green, are not frequently used. The resulting data of the color combination regularity quantitatively verify the color combination knack that is transmitted by word of mouth from generation to generation.

Using a free, open-source ray-tracing program, photorealistic spectral images have been created to show how several prisms would appear in the real world if they were made with materials that have a negative index of refraction (metamaterials). The aim of this work is to provide students with a visual interpretation of the atypical behavior of negative-index materials and a look at dispersion in the visible range in such prisms, resulting in educationally valuable outcomes.

The appearance of color stimuli can be measured psychophysically using two major techniques: (1) elementary color naming and (2) categorical color naming. On the relation between the two naming techniques, a network model (published 20 years ago) autonomously labels colors without retrieving color names from a database and has the flexibility to adapt to individual differences or observing environments. However, this network model has not been recently applied in this context as few works have focused on two types of color naming experiments using the same observers and conditions, mainly because most studies focused either on continuous changes in color appearance or on categorical color perception and did not need to employ both techniques. In our previous study, new datasets of hue and saturation judgments with whiteness and blackness evaluations were obtained. The evaluation of these datasets included elementary color naming and categorical color naming using 11 basic color terms (BCTs) with 0.5°-diameter stimuli presented at the center and 12 locations along the horizontal and vertical meridians in the visual field for three observers. The feasibility of applying the model to our new datasets in the center and near periphery has to be examined before utilizing the model for various applications. Gain factor values for each categorical color response (CCR) were individually optimized, and the same combination of gain factors were used for all locations for each observer. The results of the chi-square goodness-of-fit test indicated that the response distribution estimated by the model (color names and “undefined”) was not significantly different from the experimental data obtained in 35 out of 39 conditions. The overall average of the correct estimation was 77%. The high estimation obtained from the same gain factor values is indicative of an invariant relationship between the two naming techniques, with up to 20° eccentricity. It also shows the model's plausibility in explaining individual differences among normal observers.

Head-mounted displays (HMDs) for virtual and augmented reality applications could have severe nonuniformities due to complex optical components and the choice of light source technologies. In addition, module variations between the two eyes can result in different colors being seen with the left and right eyes. Binocular rivalry is expected for large color differences between the two eyes, which can severely affect product usability. Thus, it is important to characterize and predict the binocular rivalry in HMDs caused by interocular color differences. As a step toward this end, we propose the first binocular color difference metric, ΔE*_bino, to predict the just noticeable binocular rivalry for a pair of solid colors. A psychophysical experiment was conducted using Meta Quest 2, in which we presented different colors to the left and right eye. The collected data were analyzed to derive the metric using ROC curves. We show that the ΔE*_bino metric showed significant improvements over conventional color difference formulae. Both the ΔE*_bino formula and the anonymized experiment results are available for download.

A corpus-based quantitative assessment of Berlin and Kay's proposal is presented. We refine the Basic Color Terms hierarchy proposed by Berlin and Kay, through the concept of salience. A cross-linguistic study with 57 different languages and 136 different linguistic corpora has been conducted. This study uses KonText tool and the corpora included in it. The color labels in different languages have been obtained using a unified methodology from PanLex. We have obtained an individual hierarchy for each of the languages analyzed, as well as a general hierarchy that captures the universal trend. Results show that there is a close relationship between the evolutionary stages in the Berlin and Kay proposal and their frequency in our corpora study, which we could also relate to Zipf's Law. The only color that we certify behaves differently compared to such a proposal is yellow. The main advantage of our approach compared to previous corpora studies is taking into account the anglocentric bias by using a representative typological set of different languages from the world.

Ivrea is a small city known throughout the world as the home of the Olivetti company. For many years, the innovative urban and architectural experiment inspired and supported by Adriano Olivetti, financed by his company for a large part of the twentieth century, was less well known internationally. His patronage and his far-sighted vision for urban society  have produced results of great relevance in the history of Italian industrialization and Modern Architecture. Since 2018, the architectural assets, the archives, cultural heritage and social experiments, have become part of the UNESCO Catalogue of World Heritage Sites (Ivrea, industrial city of the 20th century). Today, many of these heritage buildings, characterized by external surfaces decorated with colored tiles of different types, have several conservation problems, due in many cases to the lack of ordinary maintenance. At the same time, the unavailability of original materials makes the planning of appropriate intervention solutions for maintenance and restoration difficult. This report intends to give an account of this event through two convergent approaches: (i) on the level of method, continually seeking a precise analysis of the materials, trying to refrain from the image of an ‘Olivetti's architecture’ flattened only on rationalist models—chromatically limited—to do justice to a less minimalist vision that has characterized the architectural heritage on matter since its inception; (ii) on the operative level, giving an account of the attempts to recover and restore that “world of colours” that is the Olivetti's city, also with a correct lexical reading of the architectural elements and the finding of materials (an operation declined toward “what can be done today”, given that many original products are unavailable and manufacturers are no longer in activity).

Among more conventional perceptual attributes, such as hue brightness and saturation, color is universally assigned a value along a warm/cool dimension. The source of this aspect of color experience is uncertain and a subject of current debate in color science. An unpublished study from the late twentieth century has recently appeared in an online archive that makes publicly available the results of an extensive set of measurements that document the variation of warm/cool values throughout color space and shows that they relate simply to the sum of the red-green and blue-yellow opponent-color activations (red+yellow vs. blue+green), which the authors suggest is consistent with a sensory basis for this distinction.