Color Research and Application最新文献

In the paper “The non-Riemannian nature of perceptual color space,” the authors analyze the data of visual experiments conducted using triad of CIE $�L^{*}$ achromatic stimuli. The statistical analysis of their results leads them to claim that the $�L^{*}$ axis cannot be endowed with a Riemannian metric coherent with observers' responses. In this communication we provide a mathematical analysis which, in our opinion, refutes the main claim of the quoted paper. Furthermore, we raise questions on the soundness of using an achromatic perceptual coordinate to describe non-chromatic perception. We inform about an alternative in which achromaticity emerges from the very act of observing colors (Provenzi E. SIAM J Imag Sci, 15(4):1944–1976, 2022; Berthier M, Provenzi E. Proc R Soc A, 478(2258):20210508, 2022).

Color significantly shapes our perceptions of the world, and extensive scientific research has explored various aspects of color, including color linguistics, aesthetics, color and marketing, color therapy, and color psychology. Notably, there has been an increasing interest in understanding the psychological domain of color in recent years. However, limited scholarly attention has been given to studying the changes in color representations and emotions over the decades. To address this gap, we utilized word embedding models of Google Books Ngrams corpus to examine the most strongly associated entities and traits with colors and their evolution in color emotions over 200 years. Analyzing three emotional dimensions—pleasure, arousal, and dominance (PAD), we found that red, green, white, black, orange, purple, brown, and pink were related to the exuberant type (+P + A + D) in PAD emotional space. In contrast, blue was linked to the relaxed type (+P−A + D), and yellow constituted the anxious type (−P + A−D). Among all basic English color terms, the emotion-driven perceptions associated with white, brown, and pink have significantly changed over time.

In the process of cataloging the estate of modernist artist Almada Negreiros, many preparatory drawings for several of the author's public artworks are currently being identified. The volume and complexity of his prolific work imply that sometimes it is hard to connect specific documents and artworks of research and preparation to their respective final works. Recently, one particular drawing proved to be the key for understanding several other documents, simultaneously contributing to clarify the artist's methodology when preparing for the large-scale stained glass behind the altar of Igreja de Nossa Senhora de Fátima. This article presents these new advances.

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.