Color Patches Research Articles

Accuracy of Hyperspectral Imaging Systems for Color and Lighting Research

ABSTRACT This study aims to compare different hyperspectral imaging devices and identify their suitability for in-situ color and lighting research. Three hyperspectral cameras were compared for radiometric, photometric, and colorimetric accuracy. The visual quality of the images obtained with each device was also evaluated to test their suitability for psychophysical experiments on color perception. The accuracies were evaluated for LED sources with correlated color temperatures ranging from 2351 K to 6922 K. The hyperspectral cameras tested were found to have acceptable radiometric accuracies for chromatic content and different photometric and colorimetric accuracies. It was also identified that a good radiometric/photometric accuracy does not necessarily indicate a good colorimetric accuracy for the same device and color. It depends on the light sources and color patches, thus highlighting the need to identify the reproduction accuracy of every test device methodically. This accuracy study thus describes a formal layout for the characterization of hyperspectral imaging devices using identifiable error metrics.

A potential deimatic display revealed in a lizard

AbstractConspicuously coloured signals may evolve via sexual selection to be ornaments or armaments, thereby conferring a fitness advantage to their bearer. Conversely, conspicuous colours may also evolve under natural selection as either aposematic signals or deimatic displays that deter attacks from predators. While conspicuous colour patches may evolve for one purpose (e.g. quality indicators), they may later be co-opted for another (e.g. anti-predator defence). Phrynocephalus mystaceus is a cryptic agamid lizard with flaps in both sexes that when folded against the head are inconspicuous, but when deployed are predicted to be highly conspicuous and to increase the appearance of body size. We tested whether head flaps play a role in social signalling via courtship or as status signals during contests in both sexes. We also tested whether the head flaps have an anti-predator function by simulating predatory encounters. Head flaps were never deployed in courtship or during contests and, therefore, are unlikely to be under sexual selection. However, head flaps and their deployment during simulated predatory encounters were consistent with the predictions associated with deimatic display theory. First, head flaps were similar in form and function between sexes. Second, they were highly conspicuous to both avian and snake predators. Third, there was a rapid transition from crypsis to conspicuousness when they deployed their head flaps during a late stage of predation, the subjugation phase, consistent with an ambush. Confirmation of the deimatic display hypothesis will require future testing of receiver responses.

Longitudinal effects of habitat quality, body condition, and parasites on colour patches of a multiornamented lizard

Ontogeny is expected to be a determinant factor affecting production of colour patches in lizards, while immune challenges or sudden weight loss may impair the maintenance of pigment-based coloration within a breeding season. We translocated males of the lizard Psammodromus algirus between two sampling plots that differed in distance to a road, vegetation structure, and predator abundance. We analysed variation in spectral reflectance of their colour patches the same and the following year. The change in the reflectance of the lizard colour patches within the first breeding season was explained by the interaction between plot and treatment, but not body condition. The maintenance of the breeding coloration was impaired only in those males translocated close to the road, probably reflecting that it is a poor-quality habitat for P. algirus. The following year, lizards that produced a more elaborate coloration were those that increased their body condition and controlled some parasitic infections, although suffered an increase of others. This study shows that colour patch production is plastic in P. algirus. Lizards increasing parasites or losing weight reduced pigmentation, although habitat quality can cushion these negative effects on pigmentation. However, not all parasites constrain the investment in coloration. In fact, some increased in those lizards that allocated more pigments to colour patches. In conclusion, longitudinal studies following experimental manipulation can contribute to understand pigment allocation rules in lizards.Significance statementPigments involved in colour patches of animals are limiting resources that can be reallocated off the skin to other functions. However, longitudinal evidence of this phenomenon is scarce in reptiles. We designed a manipulative mark-recapture experiment to investigate effects of habitat and parasitic infections on colour patch maintenance (within-year variation) and production (between-year variation) in male free-ranging lizards that were reciprocally translocated between two patches of habitat that differed in quality. During the first year, lizards translocated to the habitat with more predators and worse vegetation impoverished their coloration, while lizards translocated to the more favourable habitat maintained it despite all translocated lizards loose body condition. The next year we detected different effects on the coloration of three different parasites investigated, suggesting that coloration can reflect the virulence of the infections.

Identification of treated Baltic amber by FTIR and FT-Raman – A feasibility study

Heat-treated succinite modified under air, oxygen or inert gas atmosphere to improve its colour and clarity, was studied with Fourier-Transform Infrared and Raman spectroscopy, and referenced to variously altered untreated samples. For treated amber, the macroscopic observations revealed diagnostic features such as (1) the presence of discoidal “ sun sparkles” inside the crumbs; (2) unusual colours (e.g. dark red) for transparent specimens; (3) mottled colour patches in “beeswax” and “dragon’s blood” amber; (4) luminescence quenching; and (5) significant reduction of pine-tree resinous smell. On FTIR spectra the heat treatment of succinite is mainly marked by: (1) the intensity decrease of 2932 cm−1 band (>CH2 and –CH3), followed by the intensity increase of line at 1732 cm−1; (2) the shifts of the band from ν(C = O) towards lower wavenumbers (from 1735 cm−1 to 1714 cm−1); (3) the decrease of intensity of the band at 888 cm−1 ((=CH2 or –CH = CH–); (4) some slight distortion of “Baltic shoulder” in the region 1100–1300 cm−1. The Principal Component Analysis applied to FTIR spectra enabled to distinguish not only untreated amber from treated one, but also recognize the modifications made under oxygen conditions from the ones in an inert gas. On RS spectra of the treated Baltic amber, the heat modifications are indicated by: (1) slight value increase of the relative intensity ratio I1650/1445 compared to untreated succinite; (2) the shift of bands near 1650 (C = C) and 1445 cm−1 (CH2, CH3) towards higher wavenumbers.

The Adaptive Significance of Flash Behavior: A Bayesian Model

Some cryptic animals have conspicuous color patches that are displayed when they move. This “flash behavior” may serve several functions, but perhaps the most widely invoked explanation is that the display makes it harder for the signaler to be found by predators once it has settled. There is now some experimental evidence that flash behavior while fleeing can enhance the survivorship of prey in the manner proposed. However, to date there has been no explicit mathematical model to help understand the way in which flash displays might interfere with the search process of predators. Here we apply Bayesian search theory to show that the higher the conspicuousness of a prey item, the sooner a predator should give up searching for it in an area where it appears to have settled, although the relationship is not always monotonically decreasing. Thus, fleeing prey that give the impression of being conspicuous will tend to survive at a higher rate than prey seen to flee in their cryptic state, since predators search for flashing prey for an inappropriately short period of time. The model is readily parameterized and makes several intuitive predictions including: (1) the more confident a predator is that a prey item has settled in a given area, the longer it will search there, (2) the more conspicuous the flash display, the greater its effect in reducing predation, (3) flash behavior will especially benefit those prey with an intermediate level of crypsis when at rest, and (4) the success of flash displays depends on the predator being uncertain of the prey’s resting appearance. We evaluate the empirical evidence for these predictions and discuss how the model might be further developed, including the incorporation of mimicry which would maintain the deception indefinitely.

Revisiting congruency effects in the working memory Stroop task.

The working memory Stroop task is to name the color of a rectangular patch with keypress while holding a color word in working memory. Previous studies using this variant of the Stroop task have shown that congruency between the color patch and the color word significantly affects both color naming and working memory, with the worsening of task performance when the color patch is semantically incongruent rather than congruent with the color word. However, it remains unclear with regard to cognitive mechanisms underlying such congruency effects in the working memory Stroop task. By including a control condition among the congruent and incongruent conditions in a working memory Stroop task, the present study showed that nearly all of the working memory Stroop effect can be facilitation, and that interference, if present, is markedly smaller than facilitation in this form of the Stroop effect. There was also a critical contrast between the working memory and classic Stroop effects in terms of facilitation and interference, with larger facilitation and smaller interference in the working memory Stroop effect than in the classic Stroop effect. Moreover, working memory for a color word can be either facilitated or interfered with by the perceptual judgment (color naming) of an interposed color patch during the retention interval, depending on whether the color patch is semantically congruent or incongruent with the color word. Together, these results suggest that both facilitation and interference mechanisms can contribute to the overall congruency effects in the working memory Stroop task.

Pigment Penetration Characterization of Colored Boundaries in Powder-Based Color 3D Printing.

Color 3D printing has widely affected our daily lives; therefore, its precise control is essential for aesthetics and performance. In this study, four unique test plates were printed using powder-based full-color 3D printing as an example; moreover, the corresponding pigment-penetration depth, chromaticity value and image-based metrics were measured to investigate the lateral pigment penetration characteristics and relative surface-color reproduction of each color patch, and to perform an objective analysis with specific microscopic images. The results show that the lateral pigment-penetration depth correlates with the number of printed layers on the designed 3D test plates, and the qualitative analysis of microscopic images can explain the change in chromaticity well. Meanwhile, there is an obvious linear correlation between the mean structural similarity, color-image difference and color difference for current color samples. Thus, our proposed approach has a good practicality for powder-based color 3D printing, and can provide new insight into predicting the color-presentation efficiency of color 3D-printed substrates by the abovementioned objective metrics.

Saliency-aware color harmony models for outdoor signboard

This paper introduces a geometric approach for assessing color harmony of a signboard, and color coherence of a signboard with the environment. We propose to incorporate visual saliency as an inherent color characteristic residing in the image space, to better cope with the attention mechanism when people view a scene. In doing so, our color harmony models consider saliency-weighted color differences and area balance in CIELab color space. We collect 5.2 K valid subjective ratings on 375 diverse signboards in the real world, and translate them into quantitative measures for model construction. Experimental results show that our models improve the overall performance, especially for modeling color coherence between a signboard and the environment. The study also reveals that color combinations with similar chroma but distinctive lightness lead to harmonic signboards, while simple color patches in accordance with local context contribute to environment-coherent signboards.

Dual-channel plasmonic color prints based on deep-learning

When using a metasurface to encode multi-channel color images, in addition to nanostructural shape on the metasurface, efficiently determining nanostructural size based on the coding information has become an urgent problem. Here, we take dual-channel color prints as the research object. By modulating the silicon nanofin’s two arms’ length and the period of the meta-atom, the reflected colors are manipulated under different linearly polarized lights. According to any two color patches, to obtain the nanofin’s appropriate parameters, a dual-task cascaded neural network (DT-CNN) is designed. And the model prediction is compared with the electromagnetic simulation. Then two colorful images are used as the model input. The model output shows that the DT-CNN is useful for dual-channel color prints. In addition, it also can be applied to optical anti-counterfeiting, information storage, color display, and encrypted communication.

Research on defect detection algorithm of complex texture ceramic tiles based on visual attention mechanism

Aiming at the difficulty of detecting the surface defects of complex texture tiles, a salient target detection method based on the human visual attention mechanism is proposed and used for the detection of tile surface defects. Firstly, the image of ceramic tile surface is pretreated using the single-scale SSR light correction method and bilateral filtering method; Secondly, according to the principle of contrast and high-frequency suppression in the visual attention mechanism, aiming at the "imaging" and "aggregation" characteristics of complex background textures, a detection model based on the visual attention mechanism is established to determine and mark defects.According to the contrast principle and high-frequency suppression principle in visual attention mechanism, feature extraction of ceramic tile surface is carried out. Then, the image color patch weight salient map and image feature fused salient map are obtained, and the two maps are fused according to the image saliency criteria.Finally, the marked ceramic tile defects are determined and marked.Finally the marked ceramic tile defects are obtained. This defect detection algorithm and the other two algorithms are applied to three kinds of randomly selected complex texture ceramic tiles. The experimental results show that compared with other algorithms, our algorithm can achieve a comprehensive detection rate of more than 96% for complex texture ceramic tiles, and can obtain a good effect of ceramic tile defect detection as well.

Comparison of Natural and Dyed Fire Opal

Fire opal is much sought after for its flame-like red-orange-yellow body-color. With consumers’ enthusiasm for fire opals, dyed fire opal has gradually entered the jewelry market, which has made an impact on consumer perception and trade. In this work, we present a combined spectroscopic (FTIR, Raman, UV-Vis) investigation and chemical analysis of four natural fire opals from Mexico and Ethiopia and four dyed samples. Ultra-depth microphotographs revealed uniform color distribution in the natural fire opal, while patches of color were observed in the dyed fire opal. The main infrared peak around 1099 cm−1 indicated the hydrophane origin of all the dyed materials. The color of natural fire opals is related to the presence of Fe oxides and hydroxides (hematite, goethite) as confirmed by the Raman spectra, the first derivative of the UV-Vis spectral curves, and the relatively high Fe content by chemical analysis. By contrast, dyeing opals created several Raman peaks produced by external materials, and an extremely low Fe content was detected. The first derivative of the UV-Vis spectral curves can aid in detecting the use of a dyeing treatment in red and yellow opal.

Mechanisms in surface coloring of titanium alloy induced by picosecond laser

Various colors can be obtained on the surface of Ti-6Al-4V (TC4) alloy through picosecond pulsed laser scanning under different laser parameters, which can be expressed by the standard CMYK (cyan-magenta-yellow-black) color mode. In this paper, the microstructure and chemical components of the colored parts were investigated by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Combined with the observation of the optical microscope images, it is found that the color is produced by the oxide layer formed on the surface of TC4. In addition, the color rendering results are affected by the resolution of human eyes, laser-induced surface microstructure and proportion of different color patches. Furthermore, the relationships between laser energy, machining parameter and coloring results were qualitatively investigated, and the limiting effect of hue on saturation was clearly stated. Under the premise of appropriate laser energy, complex paintings have been successfully produced on TC4 alloy surfaces by change scanning speed and line spacing. This study offers a new approach to produce diverse colors on TC4 alloy, which may find a wide range of applications in the laser color marking.

Image naturalness model based on prototypical memory colors (sky, grass, and skin)

AbstractImage naturalness is a potent attribute to enhance image quality, and it is related to people's perception of memory colors. Many previous experiments aimed to locate the memory colors on different media. Their findings indicate that the memory colors obtained vary between color patches and images and between experimental techniques. However, there were no satisfying models with appropriate memory color centers to scale the image naturalness. This study generated an image database including three prototypical memory colors images (sky, grass, and skin) and their local processed images. First, visual naturalness and preference data were collected from a psychophysical experiment. Then, the distribution of naturalness followed by memory color positions was analyzed. Based on the distribution pattern, the ellipsoid models for each prototypical memory color were established. The results from the present memory color centers were compared with those from the other studies. Results show that the present color centers always give better prediction accuracy in image naturalness models. Finally, an image preference model was developed based on the image naturalness and colorfulness.

Implementation of the visual aesthetic quality of slope forest autumn color change into the configuration of tree species

Urban expansion leads to changes in the visual aesthetic quality and ecological degradation of the surrounding slope forest landscapes. Color is a crucial visual element to examine when viewing this large-scale slope forest landscape from a long distance. This is particularly true for the autumn color of slope forest, which is very attractive to the public. An exploration of the relationship between the change in color of a natural slope forest and its visual aesthetic quality enables the implementation of the configuration of superior aesthetic tree species. Therefore, it can provide aesthetic rules and a reference to configure local tree species to support their visual aesthetic quality, ecological sustainability and native biodiversity restoration in a local urban slope forest. However, such research is critically lacking. This study investigated the visual aesthetic quality of the color dynamics of a natural slope forest in Jiaozi Mountain, China in the autumn. We analyzed both the composition of tree species and the changes in color for each species of tree in nine forest sites that exhibited superior visual aesthetic quality. The results showed that the forests with superior visual aesthetic quality were more green, red, and yellow, had moderately higher saturation and value, more obvious color contrast, and diverse colors with primary and secondary contrast. Diverse and balanced color patches or a dominant color patch contrasted by many small patches with interspersed color components also highlighted the superior visual aesthetic quality of slope forest features. Different combinations of color features can result in high visual aesthetic quality. The 84 tree species in the superior visual aesthetic quality forests primarily displayed 10 types of color changes that varied as green, yellow, blue, red, withered yellow, withered red and gray.

Prototyping of low-cost color enhancement lighting using multicolor LEDs

We prototyped a lighting system for color enhancement with maintaining a white appearance using low-cost multicolor LEDs. We bought LEDs of several colors in local electronic parts shops, and spectral power distributions of them were evaluated for synthesizing objective lights. Five LEDs were chosen for natural color observation of the object, and three of them were used for color enhancement. Experiments were conducted using an assembled LED lighting, and a color chart and reddish and blueish color patches were enhanced with maintaining white appearance chromatically.

Concerted variation in melanogenesis genes underlies emergent patterning of plumage in capuchino seedeaters.

Coloration traits are central to animal communication; they often govern mate choice, promote reproductive isolation and catalyse speciation. Specific genetic changes can cause variation in coloration, yet far less is known about how overall coloration patterns-which involve combinations of multiple colour patches across the body-can arise and are genomically controlled. We performed genome-wide association analyses to link genomic changes to variation in melanin (eumelanin and pheomelanin) concentration in feathers from different body parts in the capuchino seedeaters, an avian radiation with diverse colour patterns despite remarkably low genetic differentiation across species. Cross-species colour variation in each plumage patch is associated with unique combinations of variants at a few genomic regions, which include mostly non-coding (presumably regulatory) areas close to known pigmentation genes. Genotype-phenotype associations can vary depending on patch colour and are stronger for eumelanin pigmentation, suggesting eumelanin production is tightly regulated. Although some genes are involved in colour variation in multiple patches, in some cases, the SNPs associated with colour changes in different patches segregate spatially. These results suggest that coloration patterning in capuchinos is generated by the modular combination of variants that regulate multiple melanogenesis genes, a mechanism that may have promoted this rapid radiation.

Development of a Screening Method for Sulfamethoxazole in Environmental Water by Digital Colorimetry Using a Mobile Device

Antibiotic resistance is a major health concern of the 21st century. The misuse of antibiotics over the years has led to their increasing presence in the environment, particularly in water resources, which can exacerbate the transmission of resistance genes and facilitate the emergence of resistant microorganisms. The objective of the present work is to develop a chemosensor for screening of sulfonamides in environmental waters, targeting sulfamethoxazole as the model analyte. The methodology was based on the retention of sulfamethoxazole in disks containing polystyrene divinylbenzene sulfonated sorbent particles and reaction with p-dimethylaminocinnamaldehyde, followed by colorimetric detection using a computer-vision algorithm. Several color spaces (RGB, HSV and CIELAB) were evaluated, with the coordinate a_star, from the CIELAB color space, providing the highest sensitivity. Moreover, in order to avoid possible errors due to variations in illumination, a color palette is included in the picture of the analytical disk, and a correction using the a_star value from one of the color patches is proposed. The methodology presented recoveries of 82–101% at 0.1 µg and 0.5 µg of sulfamethoxazole (25 mL), providing a detection limit of 0.08 µg and a quantification limit of 0.26 µg. As a proof of concept, application to in-field analysis was successfully implemented.

A simple microabrasion technique as aesthetic approach on fluorosis of anterior teeth

ABSTRACT Dentistry treatment is not only focused on restoring the function of mastication but also onthe aesthetic problem. Fluorosis is one of the aesthetic problems caused by excessive fluoride intakeduring email formation and produced color changes on the surface of the email. Fluorosis was notaffected by the aesthetics but also influenced the confidence of the patient. The Microabrasion techniqueis an option for fluorosis because it is conservative treatment with good results. A 20-year-old womanwho came to the Dental Conservation clinic complained that she wants to remove the brown color andwhite spots seen on the front teeth, which significantly interfere with her appearance. Based on clinicalexamination, many cavities were found in the back teeth of the upper and lower jaw. The results of thehistory and clinical study revealed that the patient had fluorosis in her teeth. Microabrasion was carriedout using Opalustre (ultradent). This material was applied to the tooth surface and rubbed using anapplicator (opal bristle) for 60 seconds. Then applied fluoride gel paste with finishing cup opal.Treatment results showed changes in tooth color, brown and white patches disappeared. Microabrasionis the first choice for aesthetic treatment in fluorosis and has shown satisfying results to restore thepatient's aesthetics problem. KEYWORDS: Fluorosis, microabrasion technique

Color Alignment for Relative Color Constancy via Non-Standard References.

Relative colour constancy is an essential requirement for many scientific imaging applications. However, most digital cameras differ in their image formations and native sensor output is usually inaccessible, e.g., in smartphone camera applications. This makes it hard to achieve consistent colour assessment across a range of devices, and that undermines the performance of computer vision algorithms. To resolve this issue, we propose a colour alignment model that considers the camera image formation as a black-box and formulates colour alignment as a three-step process: camera response calibration, response linearisation, and colour matching. The proposed model works with non-standard colour references, i.e., colour patches without knowing the true colour values, by utilising a novel balance-of-linear-distances feature. It is equivalent to determining the camera parameters through an unsupervised process. It also works with a minimum number of corresponding colour patches across the images to be colour aligned to deliver the applicable processing. Three challenging image datasets collected by multiple cameras under various illumination and exposure conditions, including one that imitates uncommon scenes such as scientific imaging, were used to evaluate the model. Performance benchmarks demonstrated that our model achieved superior performance compared to other popular and state-of-the-art methods.

Glucose Intake Improves Executive Attention

Glucose is the essential energy source for brain, and glucose consumption is reported to be beneficial in multiple cognitive brain functions. However, it was unclear that if oral glucose intake has any effect on improving executive attention in human subjects. In this study, we firstly investigated the effect of one-shot intake of 29 g glucose on executive attention in human subjects using an internet-based Stroop color and word test (SCWT). The time interference score, defined by the reaction times in the SCWT under three different rules, was significantly lower in the glucose intake group than in the control group. The error rate in the color patch condition of the SCWT was also significantly lower in the glucose group. These results suggest that glucose enhances executive attention.