Prediction of simultaneous contrast between map colors with Hunt's model of color appearance

The objective of this research was development of a quantitative model of simultaneous contrast (induction) to aid selection of sets of easily identified map colors. The model is an extension of R. W. G. Hunt's model of color appearance. Contrasts between central and proximal colors were used to adjust Hunt's lightness, relative redness-greenness, and relative yellowness-blueness measures. Human subject responses to CRT displays in an experiment were analyzed to produce a set of rules for selecting map colors. Rather than predict average perceptions for central/proximal color combinations, acknowledgment was made of the inherent variability in map readers' perceptions of color by developing generalized perception buffers that accounted for at least 90% of test subject responses. The task of selecting colors that will not be confused once they appear with numerous proximal colors on a map thus becomes a task of selecting colors that do not have buffers that overlap in color space. © 1996 John Wiley & Sons, Inc.     

Global color impressions of multicolored textured patterns with equal unique hue elements

A global color impression from a multicolored textured pattern can be identified. It is not clear, however, how such a single color impression can be determined from the elemental colors of the multicolored textured pattern. To investigate this question, two hypotheses were evaluated. The first hypothesis is that a single color impression is determined by the colorimetric average of the elemental colors in the textured pattern (colorimetric average hypothesis). The second hypothesis is that the impression is influenced by the color appearances of the elemental colors in the textured pattern (color appearance hypothesis). Using an asymmetrical color matching method, the authors obtained single color impressions for random‐dot textured patterns consisting of two colors with the same unique hue and brightness but each with a different saturation. Our results showed that the matched colors were not located on the line connecting the two elemental colors of the pattern, but rather were on the curved unique hue loci line. Furthermore, the chromaticities of the matches shifted toward a higher saturation than the colorimetric averages. These results support the color appearance hypothesis and suggest that a single color impression from a multicolored textured pattern is determined by a mechanism that integrates the color appearances, i.e., hue, saturation, and brightness (or lightness), of the elemental colors in the pattern. In addition, it seems that the integration of the color appearances is not a simple process, because the apparent saturation of the color impression was higher than that of the colorimetric average and the average of the chromaticities of the colors in the pattern. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 267–277, 2007     

Optimal employment of color attributes to achieve saliency in icon matrix designs

With the wide use of smart devices, through which information is presented in vast quantities, objective guidelines are needed to enable designers to choose appropriate colors for information display. The purpose of this study is to determine which colors are the most eye‐catching in displays that employ icon matrices and thereby provide empirical grounds for strengthening the visual information structure of interface designs. Three attributes of color, which include hue, tone, and color combinations, are examined to optimize the color saliency in information displays. An eye‐tracking study was conducted to evaluate saliency objectively by analyzing fixations of visual attention. Based on the hue‐saturation‐brightness color system, a 5‐by‐5 matrix of 25 color patches was adopted to generate 21 color stimuli. Part I of the study focused on hue and indicated that warm colors are perceptually more eye‐catching relative to cool and neutral colors. Part II of the study investigated tonal influences and revealed that highly saturated colors provoked the greatest visual magnetism against a black background across all hue groups, although there was an alternative tendency for a blue hue. Contrary to expectations, no distinctive patterns were observed among brightness groups. With regard to color combination, Part III of the study provided empirical verification that high contrast between a foreground and a background generates a more dominant conspicuity. The results of the present study can be applied in designing electronic interfaces that display icon matrices to create effective communication by guiding visual attention and increasing aesthetic satisfaction. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 429–436, 2015     

Effects of hue,saturation, and brightness on preference

A study was done to investigate preference responses for foreground–background color relationships. To do this, 123 university undergraduates in Ankara, Turkey, were asked to view eight background colors selected from HSB color space on which color squares of differing hues, saturations, and brightnesses were presented. Subjects were asked to show the color square they preferred on the presented background color. Findings showed that colors having maximum saturation and brightness were most preferred. Blue was the most preferred hue regardless of background. The findings for preferences for foreground–background color relationships are also included in this article. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 199–207, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10051     

Applying image‐based color palette for achieving high image quality of displays

In the highly competitive display market, manufacturers continuously develop new technologies to improve the image quality of displays. However, color measurement and visual assessment are time‐consuming to production lines. A new method to measure and improve color quality of the displays automatically therefore, is urgently needed to the manufacturers. This article proposes a familiar color correction strategy to optimize the colors of different displays by means of creating an image‐based color palette which enables color correction for familiar objects (e.g., facial skin, blue sky, or green grass) in the multidisplay systems. To produce the image‐based color palette, the 8‐bit RGB value of each pixel in an image is transformed to L*d*n* (lightness/dominant color/nondominant color) color channels, and the dominant‐color regions in an image are subsequently extracted from the dominant color (d*) channel. The memory color data of familiar objects can be set in reference monitor in advance to determine the dominant color (d*) channel. Then a series of palette colors are generated around a displayed image. The color palette will be displayed as a target for two‐dimensional colorimeter shooting to obtain the measured color data. The familiar color correction model was established based on a first‐order polynomial regression to achieve a polynomial fit between the measured color data and the reference color data on the color palette. The proposed method provides a solution to correct familiar colors on a displayed image, and maintains the original color gamut and tone characteristic in the multidisplay systems simultaneously. It is possible to achieve the preferred intent of the displayed images by using the proposed familiar color correction method. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 154–168, 2014     

Individual differences of unique hue loci and their relation to color preferences

Loci of the four unique hues (red, green, blue, and yellow) on the equiluminant plane on the color display and three preferred colors were obtained from 115 normal trichromats. We sought possible correlations between these measures. Different unique hue loci were not correlated with each other. The three preferred colors were not correlated with each other. We found five combinations of significant correlation between a preferred color and unique hue settings, yet the overall tendency is not very clear. We conclude that individual differences in color appearance measured by unique hues and color preferences measured by asking for favorite colors may not be predicted from each other or even within a category because the differences in the earlier visual mechanisms can be compensated for and these high‐level measures can be influenced by learning and experience. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 285–291, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20023     

Color names,stimulus color,and their subjective links

The aim of the research reported by this study was on the one hand to identify what colors were associated with particular words in relation to a specific language (Italian), by portraying them in color stimuli on the screen of a monitor; and on the other hand to verify whether some words of that language denoted colors that were either particularly well defined or confused with others. In an experiment using special software, the subjects were asked to produce colors directly, instead of choosing among a number of colors presented on the screen. The results showed that (i) it is possible to identify the color‐stimuli to which the terms of a language refer; that (ii) the “best” colors Giallo (Yellow), Rosso (Red), Blu (Blue), and Verde (Green) which the subjects were requested to produce were very similar to the corresponding unique hues; that (iii) among the mixed hues there were perceptually intermediate colors, that is, ones exactly midway between two consecutive unique colors: Arancione (Orange) and Viola (bluish Purple); that (iv) Turquoise and Lime were clearly positioned in the mental space of color of the participants; and that (v) for Italian speakers some hues coincide: Azzurro (Azure) and Celeste (Cerulean); Arancione (Orange), RossoGiallo (RedYellow) and Carota (Carrot); Lime and GialloVerde (YellowGreen), so that their color terms can be considered synonyms. Our most interesting finding, however, is that for Italian speakers these four mixed colors with their specific names (Lime, Turchese (Turquoise), Viola (bluish Purple) and Arancione (Orange) fall perceptually in the middle of each of the four quadrants formed in the hue circle by the four unique hues. The resulting circle is therefore characterized by eight colors of which four are unique and four are intermediate mixed. It would be advisable to repeat the study cross‐culturally to test for possible similarities and differences in color meanings with speakers of different languages. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 89–101, 2017     

Fixed range scales applied to the evaluation of color: Comparative analysis between the Munsell System and the Natural Color System

In this article, we discuss the effect of anchoring on the estimation of chromatic variables, which occurs when fixed range scales are used in psychophysical measuring. In order to do this, we compare the Munsell System and the Natural Color System (NCS), and an alternative system that employs a scale of grays as a yardstick against which to measure value and saturation. During experimentation, observers evaluated 60 matte surface color samples, following the methodology proposed by each system, but without using their respective color atlases. The data obtained reveal results that are compatible with the measurements based on the Munsell System and the NCS. By applying the gray‐scale method, the value measurements improved, whereas the saturation measurements were overestimated in samples with low reflectance. In all the cases, hue shifts were observed and thought to be attributable to the variation in luminance revealed by the samples. Judging by the similarity of the results obtained, it can be assumed that when fixed range scales are used, measurements will be anchored to their extremes, equaling every measurement made with them. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 103–112, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10130     

Dictionary‐based estimation of spectra for wide‐gamut color imaging

With the widespread use of commercialized wide‐gamut displays, the demand for wide‐gamut image content is increasing. To acquire wide‐gamut image content using camera systems, color information should be accurately reconstructed from recorded image signals for a wide range of colors. However, it is difficult to obtain color information accurately, especially for saturated colors, if conventional color cameras are used. Spectrum‐based color image reproduction can solve this problem; however, bulky spectral imaging systems are required for this purpose. To acquire spectral images more conveniently, a new spectral imaging scheme has been proposed that uses two types of data: high spatial‐resolution red, green, and blue (RGB) images and low spatial‐resolution spectral data measured from the same scene. Although this method estimates spectral images with high overall accuracy, the error becomes relatively large when multiple different colors, especially those with high saturation, are arranged in a small region. The main reason for this error is that the spectral data are utilized as low‐order spectral statistics of local spectra in this method. To solve this problem, in this study, a nonlinear estimation method based on sparse and redundant dictionaries was used for spectral image estimation—where the dictionary contains a number of spectra—without loss of information from the low spatial‐resolution spectral data. The estimated spectra are represented by a mixture of a few spectra included in the dictionary. Therefore, the respective feature of every spectrum is expected to be preserved in the estimation, and the color saturation is also preserved for any region. Experiments performed using the simulated data showed that the dictionary‐based estimation can be used to obtain saturated colors accurately, even when multiple colors are arranged in a small region. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2013     

Databases for spectral color science

In color science, spectral representation and analysis of colors have become a common approach to study color‐related problems, e.g., accurate industrial color measurement or analysis of color images. In developing algorithms for spectral color science, one often relies on existing databases of reflectance color spectra. Since a number of these databases are easily available, the same databases are commonly used by different research groups. During year 2003 the most popular one of our publicly available spectral reflectance databases was visited over 600 times. In the present article, we describe these color spectra databases and analyze their utility for spectral color science. However, the article does not take the complexity of fluorescent surfaces into account. The aim of this article is to set a solid ground for the comparisons of different methods in the spectral color science. The databases presented here include measured color spectra of natural and man‐made objects as well as spectra of some sets of standard colors. In addition to the commonly used data sets, some new data sets, including a set of standard calibrated colors and a set of natural colors, measured with 10 nm spectral resolution are introduced. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 381–390, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20244     

The representation of colors in spherical space

Color scaling experiments have established that perceived colors are distributed on the surface of a hypersphere in spherical space. A formal mathematical model of the color space is defined. Color differences as estimated by an observer are equal to the chord distance between corresponding points on the surface in spherical space. In one mathematical model are united: brightness, saturation, and hue as expressed in the empirical Munsell and NCS systems; complementary colors; large color differences; and contrast effects that are not represented in other models. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 113–124, 2008.     

Color naming experiments using 2D and 3D rendered samples

This article describes a color naming experiment using 2D and 3D rendered color samples. Conventional color naming experiments using a priori clues generally involve 2D clues such as color patches. However, in real‐world scenes, most objects have 3D shapes whose colors are affected by illumination effects such as shadows and gloss. We use 2D and 3D rendered samples as clues in the experiments, and analyze the relationship between color terms and object surfaces. First, we develop a color term collection system that can produce 218 test colors. We render the color images of a flat disk as a 2D sample and a sphere as a 3D sample on a calibrated display device. It is supposed that the 2D and 3D surfaces with the same object color are obtained under the same conditions of viewing and illumination. The results of color naming experiments show that there are differences for color terms between 2D and 3D samples. Important findings are as follows: (1) brighter color terms tend to be chosen for the 3D samples than the 2D samples, when observing achromatic colors, (2) achromatic color terms are chosen for 3D samples having low saturation, and (3) for chromatic colors, a darker color term is generally chosen in comparison to the corresponding 2D samples of the same color. These properties become more prominent by changing the illumination angle from 0° to 45° to the surface normal. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 270–280, 2015     

Variability in Unique Hue Selection: A Surprising Phenomenon

Data from ten different experiments involving nearly 600 observers of determination of unique hues are compared. Six experiments involve determination using spectral lights; two use desaturated monitor colors, and the remaining two use color chip sets. Except for unique green, color chips result in narrower ranges of results than spectral lights. Unique green has a surprisingly large range of variation in both spectral light and color chip experiments, followed by red. Comparison of spectral light data indicates that one observer's unique blue can be another's unique green and vice versa, and the same for yellow and green. This finding raises significant questions for color appearance and color space/difference models, as well as philosophy of color. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 158–162, 2004;Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10237     

Theoretical analysis of subtractive color mixture characteristics

Understanding the characteristics of the stimulus values of colors obtained by subtractive color mixture is not easy, compared with those obtained by additive color mixture, since the relationship between superimposed absorption media and the stimulus values is not simple. In this article, using the assumption of the Lambert‐Beer model for subtractive color mixture, we prove several theorems regarding the stimulus values of colors obtained by subtractive color mixture. Although these theorems are proved theoretically, numerical illustrations are also shown to confirm the theorems. The results of this paper will contribute to a systematization of subtractive color mixture. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 175–181, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10143     

Segmentation of map image using opponent color dimensions

This article describes a method for segmentation of color geographic map images based on color opponency. In this method, a color-map image is transformed into a color opponent representation as proposed for human vision. The color contrast is enhanced in a manner analogous to the opponent surround receptive fields. The enhancement process separates adjacent foreground and background regions into pairs of opponent colors. The segmentation process can then be easily completed based on this opponent structure. © 1996 John Wiley & Sons, Inc.     

Correlations between color attributes and children's color preferences

This study examined the role of color attributes (lightness and saturation) on children's color preferences for interior room colors. It also investigated children's most preferred colors among each of the five major hue families in the Munsell color system using scale‐models. Previous color preference studies have typically been done with small color chips or papers, which are very different from seeing a color applied on wall surfaces. A simulation method allowed for investigating the value of color in real contexts and controlling confounding variables. Forty‐five color samples were displayed on scale‐models to 63 children ages 7–11 years old. This study identified children's most preferred colors among each of the five major hue families in Munsell color system. It also demonstrated that saturation was positively correlated with children's preferences in the red, green, blue, and purple hue families. In the yellow hue family, interestingly, lightness has a positive correlation with preferences. Children's gender differences were found in that girls prefer red and purple more than boys. These findings lead to color application guidelines for designers to understand better color and eventually to create improved environments for children and their families. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 452–462, 2014     

A test of uniformities in the OSA‐UCS and the NCS

In the OSA‐UCS (Optical Society of America–Uniform Color Scales), except for colors on the boundary of the three‐dimensional solid (L, j, g), each color is surrounded by the 12 nearest neighboring colors that are supposed to be perceptually equally different (local uniformity). In the Swedish NCS (Natural Color System), colors are arranged so as to gradually vary in each of the three perceptual attributes: hue, ?; blackness, s; and chromaticness, c. The gradual change in an attribute may correspond to change of color difference from one to the next with a constant step (local uniformity). In each of these color‐order systems, the uniformity was tested by a color‐difference formula d? based on color‐component differences. When a coordinate is fixed (e.g., j in OSA‐UCS, or c in NCS), d? for neighboring pairs turned out fairly constant. However, systematic differences were found between d? in one coordinate and d? in another coordinate. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 277–283, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10162     

Exploring compatible facility colors and associated colors for outdoor recreational spaces

Many studies have demonstrated that people associate customary colors to buildings and facilities, and these colors significantly influence people's evaluations of the environment. However, whether customary colors also exist in the environments where building facilities have been installed is rarely discussed. Using correspondence analysis, this study explored the colors associated with five different outdoor recreational spaces (theme parks, national parks, recreational farms, riverside parks, and historic heritage sites) and fitted facility colors. The study acquired a valid sample of 103 college students and demonstrated that people judge colors in recreational spaces according to past experience and their impressions of the spaces. Hue, value, and saturation are not independent factors for color consideration; a color with a specific value and saturation is particularly suitable for some spaces. In addition, the color associated with an environment and the compatible color for facilities are not exactly the same. The possible factors that influence different environment colors and future research directions were also discussed. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 424–432, 2016     

Dependence of the color appearance of some flowers on illumination

Seven flower colors perceived by five color experts using visual color measurement under 2800 K warm white fluorescent lamps, 3500 K plant growth lamps, and 6500 K light‐emitting diodes (LEDs) were compared with those under 6500 K fluorescent lamps, which represented illuminants in florist shops. Fluorescent lamps (6500 K, 1000 lx) were found to be effective for displaying flower colors and were used as the standard condition. The colors of flowers generally shifted in the same direction as those of the illuminants in CIELAB space. The color differences were highest under the 3500 K fluorescent lamp at both 500 and 2000 lx. At 500 lx, the ΔE values under the 6500 K LED were higher than those under the 2800 K lamp. The C* and ΔE values revealed that the 2800 K lamp was unsatisfactory for purple‐blue and purple flowers and was more suitable for floral displays at lower illuminance. Under the 3500 K lamp, the highest color distortion occurred in cool‐colored flowers, but C* increased for purple‐blue and purple flowers. The 6500 K LED tended to decrease C* for warm‐colored flowers under both illuminances, but it was effective for displaying purple‐blue and purple flowers with increased C*. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 28–36, 2014     

Influence of a holistic color interval on color harmony

This study investigates how a holistic color interval, i.e., the nondirectional color difference between a pair of colors in a CIELAB uniform color space, influences perceived color harmony. A set of 1035 test color pairs displayed on a CRT was evaluated for the degree of harmony. These test color pairs consist of pairs combined from among the selected 46 test colors evenly distributed in color space. The subjects were asked to select their three preferred colors from these 46 test colors and then to evaluate the degree of harmony of the test color combinations. The color intervals (ΔE) of each test color combination were calculated and treated as values of an independent variable. In addition, the evaluated degrees of color harmony were considered as values of a dependent variable, in which statistical analysis confirmed the relationship: the degree of harmony is a cubic function of the color interval. Moreover, the plot of this relationship allowed us to identify four color intervals: roughly corresponding to the regions of first ambiguity, similarity, second ambiguity, and contrast in Moon and Spencer's model. However, our results indicated that Moon and Spencer's principles for classifying harmonious/disharmonious regions in terms of the color interval for three color attributes—lightness, chroma and hue—may be inappropriate in predicting perceived color harmony. As for the color intervals between a pair of colors considered as a function of the three attributes, the interval for lightness may have a predominant effect on color harmony, expressed in terms of a cubic relationship. Results of the study further demonstrated that the subject's choice of colors significantly influences perceived color harmony. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 29–39, 2001