Colorimetric Attributes Research Articles

Colour gamut analysis of low‐cost dye‐sensitised solar cells using natural dyes

AbstractDue to the increasing effects of greenhouse gases and environmental pollution, the need for new clean energies like solar energy attracts much attention. Although the characteristics and the efficiency of green photovoltaic devices have been researched, the colour gamut achievable from those devices has not been studied. This study investigates the colour gamut of low‐cost dye‐sensitised solar cells (DSSCs). To do this, 14 natural dye extracts were obtained from herbal resources including dragon fruit, blueberry, mango, radish, yellow rose, red cabbage, sour pomegranate, beetroot, olive, green cabbage pepper, eggplant, parsley, bramble and cherry, and employed as photosensitiser in solar cells. Then, the colorimetric attributes of the photosensitisers were studied in three‐dimensional (3D)‐colour space, that is, CIELab, CIELCH and CIE1931 chromaticity diagram. Additionally, the convex hull method was employed to determine the colour gamut boundary and the corresponding colour gamut volume. Results showed that the majority of samples benefited from approximately 3°–82° of hue angle in a*b* diagram of CIELab colour space and showed the yellowish to reddish tint effects. In CIELCH colour order system, cherry and parsley showed the lowest and highest lightness attributes while the chroma property of samples varied from minimum 1.2 for eggplant to maximum 60.2 for the dragon fruit. Moreover, the results of using the convex hull method showed the volume of 7.73 × 104 that is bounded by the colour gamut of 3D colour points over the CIELab colour space.

POINT CLOUD SEGMENTATION IN HERITAGE PRESERVATION. ADVANCED DIGITAL PROCESS FOR HISTORICAL HOUSES

Abstract. This paper discusses the use of point cloud segmentation, both automatic and semi-automatic, in heritage conservation processes, with the aim of consciously integrating traditional and innovative methods. Thus, the research explores the potential of open-source software tools for semi-automatic point-cloud segmentation in enriching heritage knowledge and contributing to the inspection of its state of conservation. This ensures a 3D geometric view of reality and enables the identification of criticalities that may not be visible to the naked eye through colorimetric attributes. The study was conducted on Villa Leonardi, a historical house located in the city of Treia in the Marche Region (Italy) as a pilot test. The investigation focused on the east and south elevations of the building, which were suitable for two distinct trials: a semi-automatic procedure for analyzing the quality of mortar joints in an exposed masonry, and a semi-automatic procedure for mapping alterations and decay in a plastered masonry. To validate the results, manual and semi-automatic maps were compared using both qualitative and quantitative assessments. Qualitative assessment involved overlay and visual analysis, while quantitative assessment involved transforming the segmented point cloud into a mesh and calculating the resulting surface area. The critical interpretation of the two trials revealed both advantages and disadvantages; overall, experimentation highlighted the added value that advanced digital process can bring to the issue of heritage preservation.

Eco-friendly dyeing of cotton fabric using used tea bag extracts: A comprehensive study on pH, fabric cationisation, and computational analysis

The present study aims to explore the eco-friendly dyeing of cotton fabric using extracts from used tea bags, without the need for any metal mordant. Additionally, this research delves into the intricate relationship between pH levels and fabric cationisation, exploring their combined impact on the functional properties of naturally dyed cotton samples. Preceding the dyeing process, the cotton fabric underwent cationisation through the application of 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHPTAC) at varying percentages. Subsequently, the fabric was dyed with tea liquor at different concentrations and pH levels. The ensuing investigation encompassed an assessment of color fastness and colorimetric attributes (CIELab, CIELch, ΔE, and K/S) of the dyed cotton fabrics. Furthermore, FTIR analysis was employed to augment our understanding of the dyeing process, while UV-Vis spectroscopy facilitated the quantification of exhaustion and fixation percentages. The results indicate that the highest exhaustion percentage of 88.6% was achieved at pH 13 for cationised fabric with a cationiser concentration of 55 g/L. In comparison, the non-cationised fabric exhibited an exhaustion percentage of 0.75%, while the mordanted (KAI(SO₄)₂.12H₂O) fabric showed 3.6%. Furthermore, the cationised fabric displayed excellent colour fastness to washing, rubbing, and perspiration (rated 4–5) compared to the non-cationised fabric. The stronger interaction calculated with density functional theory (DFT) between theaflavins, one of the primary colour components of tea dye, and cationised cellulose monomers explains the enhanced washing and rubbing fastness observed. The findings emphasize the significant influence of pH and fabric cationisation on dyeing and the functional properties of the dyed fabric.

Using colorimetric methods to analyze the impact of acrylic binders' physical-chemical factors on dirt-pickup resistance of white façade coatings

Building façade is one of the most significant factors to make the city glamorous; for this reason, special attention should be paid to the cleanness of buildings' exterior surface from pollution. This work intends to study the effect of physical-chemical parameters of acrylic façade coatings on its dirt-pickup resistance. Five pigmented white coatings based on five acrylic resins, and the corresponding clear coatings were prepared. Then, using dirt simulating past, half of the pigmented- and clear-coatings was contaminated. After cleaning the contaminated area, the dirt-pickup resistance of both clear and pigmented coatings was investigated through colorimetric methods. FTIR and DSC were used to analyze the physical and chemical properties of the acrylic resins. Besides, contact angle and water uptake were measured. Finally, the correlations between the physical-chemical parameters of acrylic binders and their colorimetric attributes were studied. Results showed that the higher glass transition temperature, lower water uptake, lower δ C-OH/ν CH ratio, and higher water droplet contact angle results in a better dirt-pickup resistance.

Examining Spatial Attributes for Color Deficient Observers

Color deficiency is a common affliction for males, with about 8% of the male population suffering from some form of – colloquial – color blindness. In common description, this is interpreted as the inability to perceive certain colors from a sensory standpoint. If that description is sufficiently complete, spatial attributes of the color signal should not influence the visual experience of a Color Deficient Observer (CDO).In this paper we describe the set-up and results of an experiment that is intended to vary the spatial attributes of a color deficiency test when shown to an observer. For this, we modified color vision charts to maintain their colorimetric attributes while varying spatial attributes and we measured color deficient observers with respect to their response accuracy and their response speed. We show results that indicate that there is a clear influence of color proximity in the responses.

Classification of Bee Pollen and Prediction of Sensory and Colorimetric Attributes-A Sensometric Fusion Approach by e-Nose, e-Tongue and NIR.

The chemical composition of bee pollens differs greatly and depends primarily on the botanical origin of the product. Therefore, it is a crucially important task to discriminate pollens of different plant species. In our work, we aim to determine the applicability of microscopic pollen analysis, spectral colour measurement, sensory, NIR spectroscopy, e-nose and e-tongue methods for the classification of bee pollen of five different botanical origins. Chemometric methods (PCA, LDA) were used to classify bee pollen loads by analysing the statistical pattern of the samples and to determine the independent and combined effects of the above-mentioned methods. The results of the microscopic analysis identified 100% of sunflower, red clover, rapeseed and two polyfloral pollens mainly containing lakeshore bulrush and spiny plumeless thistle. The colour profiles of the samples were different for the five different samples. E-nose and NIR provided 100% classification accuracy, while e-tongue > 94% classification accuracy for the botanical origin identification using LDA. Partial least square regression (PLS) results built to regress on the sensory and spectral colour attributes using the fused data of NIR spectroscopy, e-nose and e-tongue showed higher than 0.8 R2 during the validation except for one attribute, which was much higher compared to the independent models built for instruments.

Determining Tolerance Values of Instrumentally Measured Color Differences to Evaluate Black Filament Yarns

There are many factors affecting the tolerance values of instrumentally measured color differences, including variety of industries, type of products to be matched with the original samples, the need of customers, etc. Regarding the insufficiency of various color difference formulae to deal with the acceptability of color matching of reproduced samples with the target, some researchers tried to present an instrumental color tolerance limit in accordance with the results of visual assessment experiments. Considering the specific colorimetric attributes of achromatic samples (with low lightness and chroma values), it was tried to set an instrumental tolerance limit based on the measured and visually perceived color differences between 20 filament black yarns and the reference one. The results showed that determining the color tolerance value based on various color difference formulae, i.e. ΔEa*b*, CIE94, CIE2000 and CMC (2:1), results in different instrumental wrong decisions, while the ΔE*ab color difference equation with the color tolerance value of 0.5 for filament black yarns showed the minimum number of wrong decisions.

Correlating emulsion characteristics with the properties of active starch films loaded with lemongrass essential oil

Edible films supplemented with active ingredients are promising for food packaging and preservation. Numerous plant essential oils present antimicrobial activity against pathogenic microorganisms, but their low solubility in water limits food-related applications. Emulsification is herein exploited as a means of improving the dispersion of such active substances in water, imparting increased functionality and reduced degradation. Lemongrass essential oil (LEO) was directly emulsified as dispersed phase into aqueous solutions of pectin, which was used together with Tween 80 as polymeric emulsifiers. LEO nano- and micro-sized droplets were added to film-forming formulations based on glycerol-plasticized cassava starch (TPS) and then dried into films by continuous casting. LEO contents in films relied upon microbiological assays to ensure antimicrobial activity. Films’ chemical composition, morphological, thermal, mechanical, and barrier properties, in addition to biodegradability in vegetal compost, were comprehensively studied. In general, emulsions were suitably dispersed within the TPS matrix, both phases showing good interaction and compatibility. Emulsification caused important changes in the TPS-based films, such as improved colorimetric attributes, thermal stability, barrier to moisture, and mechanical properties. Another key observation was the maintenance of the biodegradation profile in soil of TPS after the addition of LEO emulsions. Overall, the emulsification approach was successful in providing TPS films with multifunctionality by the supplementation of an active substance without negatively affecting its fundamental properties for food packaging applications.

Pretreatment effects on pigment‐based textile inkjet printing – colour gamut and crockfastness properties

The application of two commercial pretreatment agents, formulated to improve the performance of a six‐colour nano‐scale pigment ink set during the textile inkjet printing of cotton and polyester (PET) fabrics, was examined. An industrial scale printer, operating at 55 linear m/h and equipped with Kyocera printheads, was used to print on commercial fabrics (180 cm wide) prepared for digital printing. The work employed an industrial scale rather than a benchtop printer to enhance the utility of the results for a commercial environment. The colorimetric attributes of printed fabrics were recorded for the individual inks as well as for spot colour combinations generated using Dr. Wirth RIPMaster v11 software. Colour table profiles were also generated and the colorimetric values of inks were compared. Colour gamuts of inks on cotton and PET, including three‐dimensional volumes in the CIELab space, were examined to assess the role of pretreatment on the colorimetric properties of the printed substrates. It was found that the pretreatments enhanced the ink receptiveness, colour intensity and colour gamut of fabrics. Pretreatment of cotton resulted in a larger gamut and more vivid colours than on PET. However, wet and dry crockfastness results were found to be low. In this regard, Time‐of‐Flight Secondary Ion Mass Spectrometry analysis of fabrics printed in the presence and absence of pretreatment indicated that the low crockfastness arises from higher pigment levels on the surface of the pretreated fabric.

Determining the colorimetric attributes of multicolored materials based on a global correction and unsupervised image segmentation method.

Fast and accurate measurement of colors in multicolored prints using commercial instruments or existing computer vision systems remains a challenge due to limitations in image segmentation methods and the size and complexity of the colored patterns. To determine the colorimetric attributes (L*a*b*) of multicolored materials, an approach based on global color correction and an effective unsupervised image segmentation is presented. The colorimetric attributes of all patches in a ColorChecker chart were measured spectrophotometrically, and an image of the chart was also captured. Images were segmented using a modified Chan-Vese method, and the sRGB values of each patch were extracted and then transformed into L*a*b* values. In order to optimize the transformation process, the performance of 10 models was examined by minimizing the average color differences between measured and calculated colorimetric values. To assess the performance of the model, a set of printed samples was employed and the color differences between the predicted and measured L*a*b* values of samples were compared. The results show that the modified Chan-Vese method, with suitable settings, generates satisfactory segmentation of the printed images with mean and maximum ΔE00 values of 2.43 and 4.28 between measured and calculated values.

Effect of orange peel attribute of automotive finishes on their blackness perception

In this paper, the perceived blackness of 10 specific automotive finishes with different levels of orange peel attribute is investigated under the diffuse illumination condition. Since the purchased ACT black panels had approximately the same colorimetric attributes, i.e., lightness, hue, and chroma, the effect of colorimetric properties on perceived blackness was minimized. Thirty nonexpert observers including 14 males and 16 females were selected to compare the blackness perception of ACT black panels. The observers’ normal color vision was already evaluated by applying the Ishihara test method. The black panels were ranked from the minimum perceived blackness to the maximum by employing the pair comparison method and performing 1800 visual assessments. Results showed that, in general, the blackness perception of panels increased with a decrease in their orange peel attributes, but the orange peel attribute is not the only factor affecting the perceived blackness of black panels. Besides, while the black panels were colorimetrically too close to each other, the panel with the lowest lightness and chroma value was assessed as the blackest sample among the ACT panels with the lowest orange peel attribute.

A study of the effects of fabric pretreatment on color gamut from inkjet printing on polyester

This paper pertains to characterizing the effects of a commercial pretreatment agent formulated specifically for digital printing on polyester (PET) fabric using pigment-based inks. Emphasis was placed on evaluating the colorimetric attributes of individual and mixed inks, from color patches generated using Dr Wirth RIPMaster V11 software and on developing an approach to addressing color-bleeding problems that can occur from inkjet printing on PET. In addition, 3-D color gamut analysis was undertaken using Origin software. Results indicated that the pretreatment increased color intensity, improved print quality and enlarged the color gamut. In another set of experiments, the use of different ink limits indicated no obvious change of color gamut using the same print mode, which afforded an opportunity to reduce ink consumption, thus the cost in large-scale production, and minimize color bleeding. To aid the potential commercial utility of the outcomes of this investigation, an industrial scale inkjet printer (MS JP5 evo) was used.

Enhancing the Color Performance of Pigment Inkjet Printing of Cotton Fabric by Electrostatic Attraction Force

The properties of ink dots determine the color performance of inkjet printed fabrics. The purpose of this study was to enhance the color performance of pigment inkjet printing using the electrostatic attraction force. A cationic modifier was used to pretreat cotton fabric prior to inkjet printing with pigment inks in which the pigment particles were negatively charged on the surface. The spreading test of pigment ink droplet (4.0 μL) was conducted both on the untreated and modified fabrics. The effective porosity of cotton fabric was calculated and its correlation with the Zeta potential of pigment inks was studied. The ink dots on the inkjet printed fabrics were observed under a digital microscope. The colorimetric attributes demonstrated that keeping the pigment particles on the fabric surface by the electrostatic attraction force was helpful to improve the color performance of pigment inkjet printing. The 2-dimensional color gamut of (a∗, b∗) was enlarged by 13.4% on the modified fabric as compared to the untreated fabric.

Color appearance modeling of bicolor striped woven fabrics considering neighboring color effects

AbstractIn this article, the effect of the spatial and colorimetric attributes of neighboring color on color appearance shift in bicolor striped woven fabrics is investigated. A total of 240 test/neighboring woven color combinations were constructed in four different striped paradigms. Each test color in the combinations was visually assessed by 12 observer panels with the use of the magnitude estimation method estimating the magnitude of perceptual color attributes lightness, colorfulness, and hue. The visual estimates obtained were analyzed statistically by employing correlation and simple regression methods, and, as a result, the following significant neighboring color effects were detected and individually defined: (1) neighboring color's size, lightness, colorfulness, and hue on test color's lightness, (2) neighboring color's colorfulness and hue on test color's colorfulness, and (3) neighboring color's hue on test color's hue. Furthermore, through multiple regression analysis, color appearance models by which the lightness, colorfulness, and hue of bicolor woven fabrics can be predicted were derived. The predictive performance of the models was evaluated by calculating the difference between the visually estimated and the predicted color appearances, using ΔL*, ΔC*, Δh°, and ΔECMC(2:1). Among all the derived models, the model producing the smallest mean error was chosen as a final model, and its great accuracy in color appearance predictions was verified through further statistical evaluation. It is envisaged that the findings of this research are of benefit to design textile products with bicolor striped woven fabrics to have desired color appearances. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 512–521, 2017

Colorimetric analysis of black coated fabrics

In this article, two visual evaluation methods, i.e., the rank-ordering and pair comparison techniques, are sequentially used to investigate the effect of hue, lightness, and chroma values on the preference of blackness of 216 black coated fabrics. Based on the colorimetric attributes of specimens, the blackness preference of samples is assessed by 18 amateur observers through different predesigned experiments. Results show that while the lightness of samples performs a very important role in the blackness preference, it does not individually influence the results, and irrespective of the effect of chroma, observers perceive bluish-cyanish black fabrics as the preferred black samples. However, the specialized functionality of lightness is evident for black coated fabrics with very close hue and chroma attributes, and the blackness preference of samples increases when lightness is decreased. Finally, the validity of some suggested blackness indices is evaluated with comparison to the visual results.

Crosscultural comparison of color terms and preference of persimmon‐dyed fabric, Galchon

AbstractThis crosscultural study was aimed at correlating color emotions and preference for persimmon‐dyed cotton fabrics known as Galchon. Cotton fabrics were dyed with persimmon powder, in a range of shades, and in some cases were also iron mordanted. Textile and fashion students from Jeju National University in Korea and North Carolina State University (NCSU) in USA participated in the visual assessment of dyed samples and were asked to scale their visual experience and state their emotion and preference for the terms “Bright,” “Heavy,” “Soft,” “Strong,” “Deep,” and “Like.” Korean observers used “Strong” for iron‐mordanted Galchon, and American observers did not associate “Bright” or “Deep” with weakly dyed fabrics. In addition to the subjective terms described, the color preference for samples was quantified using their CIE colorimetric attributes. For Korean observers, the results indicate a correlation between L* and “Bright,” whereas for Americans a stronger correlation was obtained against “Soft.” American observers' results also show a relationship between C* and the term “Warm,” especially for dyeings of Galchon at high concentrations. It was also found that iron mordanting affected responses from both groups but only influenced the color preference of Korean observers. © 2015 Wiley Periodicals, Inc. Col Res Appl, 40, 592–604, 2015

Effect of Lightness on Blackness Preference of Black Fabrics

In this paper, the effect of lightness on blackness preference of 216 black fabrics prepared by printing method is investigated. 18 observers including of 9 males and 9 females are asked to firstly rank order black fabrics with the same lightness values according to their preference. In the next step, observers are asked to define their blackness preference for blacks with different L values. Results show that while there are some neutral black fabrics, observers mostly prefer bluish-cyanish blacks. Besides, samples with the higher values of lightness and chroma are not preferred by observers especially if their hue angles lie in the first quarter of the hue area, i.e., 0-90o. Meanwhile, samples with the lowest lightness values are not preferred by most of observers because of their high chroma values. This achievement proves that lightness is not the only colorimetric attributes which influences on blackness preference.

Pulsed electric field treatment prior to freezing carrot discs significantly maintains their initial quality parameters after thawing

SummaryThe interaction of pulsed electric fields (PEF) with different cryoprotectant and texturizing agents in quality retention of carrot discs was analysed. Increasing the permeability properties by PEF may lead to better accessibility of intracellular materials to freezing and thus reducing the freezing time, leading to better maintaining the texture after thawing. Carrot discs of 5 mm thickness were immersed in different solutions of CaCl2, glycerol, trehalose and tap water, and subsequently were treated with PEF (1 kV/cm, 100 pulses, 4 Hz). Then, the samples were drained and packed along with a control group in separate prepared polypropylene pouches. All the samples were frozen at −18 °C for 24 h and thawed during 3 h at ambient temperature (20 °C) the following day. The quality of the thawed carrot discs was certified by measuring weight loss, firmness, microscopic studies and CIE colorimetric attributes. All the PEF‐treated samples, no matter what solution they were soaked in, could significantly (P < 0.05) maintain the firmness as well as colour attributes. However, it was deducted that application of CaCl2 in conjunction with PEF can result in a firmer texture. Firmness analyses determined that application of PEF alone results in 5.84 N, while its combination with CaCl2 leads to higher value of 6.63 N. Firmness in control samples was found to be 3.46 N. The SEM studies supported the results of firmness analysis and depicted more integrity in the cell walls of the samples treated with CaCl2 and glycerol. The weight loss values varied among different samples, and the highest amount and lowest amount were reported in CaCl2 and solely PEF‐treated samples, respectively. There was no significant difference between the colour attributes measured in different groups including control sample (P > 0.05).

Saliency for Spectral Image Analysis

We introduce a new feature extraction model for purposes of image comparison, visualization and interpretation. We define the notion of spectral saliency, as the extent to which a certain group of pixels stands out in an image and in terms of reflectance, rather than in terms of colorimetric attributes as it is the case in traditional saliency studies. The model takes as an input a multi- or hyper-spectral image with any dimensionality, any range of wavelengths, and it uses a series of dedicated feature extractions to output a single saliency map. We also present a local analysis of the image spectrum allowing to produce such maps in color, thus depicting not only which objects are salients, but also in which range of wavelengths. A variety of applications can be derived from the resulting maps, particularly under the scope of visualization, such as the saliency-driven evaluation of dimensionality reduction techniques. Results show that spectral saliency provides valuable information, which do not correlate neither with visual saliency, second-order statistics nor with naturalness, but serve however well for visualization-related applications.

Effect of Colorimetric Attributes on Perceived Blackness of Materials

Effect of Colorimetric Attributes on Perceived Blackness of Materials