Color Difference Measurement Research Articles

Efficient Computation of Geodesics in Color Space.

Although scientists agree that a perceptual color space is not Euclidean and color difference measures, such as CIELAB's ∆E2000, model these aspects of color perception, colormaps are still mostly evaluated through piecewise linear interpolation in a Euclidean color space. In a non-Euclidean setting, the piecewise linear interpolation of a colormap through control points translates to finding shortest paths. Alternatively, a smooth interpolation can be generalized to finding the straightest path. Both approaches are difficult to solve and are compute intensive. We compare the 11 most promising optimization algorithms for the computation of a geodesic either as the shortest or as the straightest path to find the most efficient one to use for colormap interpolation in real-world applications. For two control points, the zero curvature algorithms excelled, especially the 2D relaxation method. For multiple control points, only the mimimal curvature algorithms can produce smooth curves, amongst which the 1D relaxation method performed best.

Influence of biodegradable polymer films on conformation of polydiacetylene–silver nanocomposites as colorimetric time–temperature indicators

Time–temperature indicators (TTIs) are used to monitor the quality of packaged products by providing a visual indication of product deterioration due to time and temperature during transportation, storage, and distribution. This study aimed to investigate the effect of biodegradable polymer films on the limits of the color change mechanism in polydiacetylene. TTIs were prepared using biodegradable polymer films based on carboxymethyl cellulose, polyvinyl alcohol (PVOH), chitosan, and carboxymethyl chitosan (CMCh) with thermochromic properties provided by silver nanoparticles–polydiacetylene (10 % w/w AgNP–PDA). Vesicle and core–shell structures of AgNP–PDA appeared in the chitosan- and PVOH-based films owing to the effects of functional groups in the base polymer. Total color difference measurements indicated that the AgNP–PDA-containing films exhibited color changes in response to storage at 35 ℃ for a total of 14 days. Specifically, the AgNP–PDA in the chitosan- and PVOH-based films produced noticeable color changes from blue to reddish-purple or reddish-brown, respectively, which was influenced by the core–shell structure of AgNP–PDA embedded in the base polymer. The developed films are very promising for applications as TTI devices for tracking fresh products, supported by the compatibility of activation energy (Ea) from 29 to 79 kJ/mol.

ColorNetVis: An Interactive Color Network Analysis System for Exploring the Color Composition of Traditional Chinese Painting.

In the field of digital humanities, color research aims to discover explanations for painting history and color usage habits. However, researchers analyzing color relationships is challenging and time-consuming, as it requires color extraction and a detailed review of many painting images for reference and comparison of color relationships. In our work, we propose ColorNetVis, an interactive color network analysis tool that enables researchers to explore color relationships through color networks. The core of ColorNetVis is a bipartite network model that establishes a bipartite relationship between colors and Chinese painting within a scope based on color difference measurement. It constructs a one-mode color network through projection algorithms and similarity calculation methods to discover the relationship between colors. We propose a coordinated set of views to demonstrate the combination of determined color networks with painting types and real-world attributes. We use color space view, color attribute distribution view, and single color query components to assist researchers in conducting detailed color analysis and validation. Through case studies, researcher reviews, and user studies, we demonstrate that ColorNetVis can effectively help researchers discover knowledge of color relationships and potential color research directions.

Effect of the Different Dietary Supplements on the Average Surface Roughness and Color Stability of Direct Restorative Materials Used in Pediatric Dentistry.

Increased surface roughness and discoloration of the direct restorative materials used in pediatric patients affect the longevity of restorations and impair children's oral health. Many factors can alter these properties. One of these factors is the intake of dietary supplements. It is crucial to predict the properties of restorative materials when exposed to dietary supplements to maintain the dental care of children. Thus, this study aimed to investigate the effect of various syrup-formed dietary supplements on the average surface roughness and color stability of current restorative materials used in pediatric dentistry. Seven different restorative materials (conventional glass ionomer [Fuji IX GP], resin-modified glass ionomer, [Fuji II LC], zirconia-reinforced glass ionomer [Zirconomer Improved], polyacid-modified composite resin [Dyract®XTRA], bulk-fill glass hybrid restorative [Equia Forte HT Fill], conventional resin composite [Charisma Smart], and resin composite with reactive glass fillers [Cention N]) were tested. The specimens prepared from each type of restorative material were divided into five subgroups according to dietary supplements (Sambucol Kids, Resverol, Imunol, Umca, and Microfer). These specimens were immersed daily in supplement solution over a period of 28 days. Surface roughness and color difference measurements were performed at baseline and at the 7th and 28th days. The color difference and Ra values showed that there was an interaction among the type of restorative material, type of dietary supplement, and immersion time factors (p < 0.05). Whereas lower Ra values were found in the composite resin group, the highest Ra values were found in the conventional glass ionomer group. All supplements caused increasing color difference values, and Resverol and Umca showed higher discoloration values above the clinically acceptable threshold. The intake of dietary supplement type, the immersion time of the dietary supplement, and the restorative material type affected the surface roughness and color stability of the tested direct restorative materials. All of the experimental groups showed higher Ra values than clinically acceptable surface roughness values (0.2 µm). The color difference values also increased with the immersion time.

Flexible transparent wood with reversible photoresponsive property

Flexible photoresponsive transparent wood (FPTW) has potential applications in electronic equipment, sensors, and other fields. In this study, flexible and photoresponsive transparent wood was synthesized through the impregnation process, utilizing epoxy resin and a spiropyran solution. This process endowed the wood with intelligent response and flexible capabilities. Scanning electron microscopy (SEM) revealed the impregnation of the flexible polymer into the porous structure of natural wood. Further validation was conducted to affirm the sample responds to ultraviolet light, employing analyses of infrared spectroscopy, UV–visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). Through the measurement of chromaticity parameters, encompassing lightness (L*), redness (a*), yellowness (b*), and total color difference (ΔE*), before and after UV irradiation, it is indicated that the wooden samples manifest commendable photoresponsive properties. Testing the fluorescence properties of the samples, the spiropyran completed the opened-loop and closed-loop transitions under irradiation with UV and visible light. In addition, the FPTW has excellent mechanical properties, with a tensile strength of 0.98 GPa and an elastic modulus of 0.65 GPa.

Physicochemical properties and antibacterial mechanism of theabrownins prepared from different catechins catalyzed by polyphenol oxidase and peroxidase

Theabrownins (TBs) are the characteristic functional and quality components of dark teas such as Pu'er tea and Chin-brick tea. TBs are a class of water-soluble brown polymers with multi-molecular weight distribution produced by the oxidative polymerisation of tea polyphenols during the fermentation process of dark tea, both enzymatically and non-enzymatically. TBs have been extracted and purified from dark tea all the time, but the obtained TBs contain heterogeneous components such as polysaccharides and caffeine in the bound state, which are difficult to remove. The isolation and purification process was tedious and required the use of organic solvents, which made it difficult to industrialise TBs. In this study, epigallocatechin (EGC), epigallocatechin gallate (EGCG), epigallocatechin gallate (ECG), EGC/EGCG (mass ratio 1:1), EGCG/ECG (mass ratio 1:1), EGC/ECG (mass ratio 1:1) and EGC/EGCG/ECG (mass ratio 1:1:1) as substrates and catalyzed by polyphenol oxidase (PPO) and peroxidase (POD) in turn to produce TBs, named TBs-dE-1, TBs-dE-2, TBs-dE-3, TBs-dE-4, TBs-dE-5, TBs-dE-6 and TBs-dE-7. The physicochemical properties and the antibacterial activity and mechanism of TBs-dE-1–7 were investigated. Sensory and colour difference measurements showed that all seven tea browning samples showed varying degrees of brownish hue. Zeta potential in aqueous solutions at pH 3.0–9.0 indicated that TBs-dE-1–7 was negatively charged and the potential increased with increasing pH. The characteristic absorption peaks of TBs-dE-1–7 were observed at 208 and 274 nm by UV-visible (UV-vis) scanning spectroscopy. Fourier transform infrared (FT-IR) spectra indicated that they were phenolic compounds. TBs-dE-1–7 showed significant inhibition of Escherichia coli DH5α (E. coli DH5α). TBs-dE-3 showed the strongest inhibitory effect with minimum inhibitory concentration (MIC) of 1.25 mg mL–1 and MBC of 10 mg mL–1, followed by TBs-dE-5 and TBs-dE-6. These three TBs-dEs were selected to further investigate their inhibition mechanism. The TBs-dE was found to damage the extracellular membrane of E. coli DH5α, causing leakage of contents, and increase intracellular reactive oxygen content, resulting in abnormal cell metabolism due to oxidative stress. The results of the study provide a theoretical basis for the industrial preparation and product development of TBs.

Lignins and Lignin Derivatives as Dispersants for Copper Phthalocyanine Pigment Nanoparticles

Copper phthalocyanine (CuPc) is a widely used organic blue pigment with color brilliance, light fastness, and low cost. However, its poor dispersibility in aqueous solutions limits the water-borne application. Lignin’s hyperbranched polymer structure makes it a potential dispersant. In this study, lignin is functionalized with carboxylic acid (−COOH) and amine (−NH2) to enhance the interaction with aqueous solutions. Their applications as dispersants for CuPc in aqueous solutions are investigated together with commercially available alkali lignin, dealkali lignin, and lignosulfonate. The effectiveness of dispersion stability is evaluated by the suspension stability. Lignin-NH2 enhanced the suspension stability of CuPc to allow 94 wt % CuPc particles to remain suspended in water for 24 h compared to 24.4 wt % with no dispersant added. The mechanism of dispersion is revealed by the measurements of zeta potential and particle size, as well as the calculation of lignin adsorption amount on CuPc. Moreover, the lignins are applied to disperse CuPc in acrylic resin as a water-based paint application. With the aid of lignin-NH2 dispersant, CuPc enhances the tinting strength to 110.75% without altering the blue color through color difference measurements. Lignin-NH2 contributes to both better suspension stability and tinting strength than a commercially available dispersant dioctyl sodium sulfosuccinate (DOSS).

Impact of Low-Pressure Plasma Treatment of Wool Fabric for Dyeing with PEDOT: PSS.

This study presents the effect of non-thermal plasma modification on the changes of surface morphology, color characteristics and electrical conductivity of wool fabric dyed with intrinsically conductive polymer (ICP) poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS). The wool fabric was treated with an aqueous dispersion of PEDOT: PSS, Clevios F ET, providing electrically conductive properties to textiles. The wool fabric, containing basic groups of amines (NH2), was pre-activated with low-pressure plasma of non-polymer forming nitrogen (N2) gas before exhaust dyeing with PEDOT: PSS at 90 °C was applied. This treatment imparted hydrophilicity, reduced felting, increased adhesion, improved dye ability and ensured that more PEDOT: PSS negatively charged sulfonate counter ions would be electrostatically bounded with the cationic protonated amine groups of the wool fiber. Initially, before (N2) plasma treatment and after fabrics were evaluated according to the test method for aqueous liquid repellency, the surface morphology of the plasma-modified and -unmodified wool dyed fabric was observed with scanning electron microscopy (SEM). The functional groups introduced onto the surface after N2 gas plasma treatment of wool fabric were characterized by X-ray photoelectron and FTIR-ATR spectroscopy. The results of color difference measurements show that N2 gas plasma treatments provide more intense color on Clevios F ET dyed wool fabric and retain its electrical conductivity.

Alleviating Heavy Metal Toxicity in Milk and Water through a Synergistic Approach of Absorption Technique and High Voltage Atmospheric Cold Plasma and Probable Rheological Changes.

In this study, we combined atmospheric pressure cold plasma, a novel treatment technology, with an absorption technique with soybean husk to remove Pb and Cd from milk. Different combinations of treatment duration, voltage, and post treatment retention time were used to determine the effectiveness of cold plasma. Soybean husk was used for metal extraction, and it was observed that when the milk samples were plasma treated with a discharge voltage of 50 kV for 2 min and held for 24 h, the highest mean elimination of about 27.37% for Pb and 14.89% for Cd was obtained. Reactive oxygen and nitrogen species produced from plasma treatment were identified using Optical Emission Spectra analysis. A high voltage of 50 kV plasma for a 2 min duration could produce 500 ± 100 ppm of ozone concentration inside the treated package. The value of ΔE, which indicates overall color difference measurement, was significantly (p < 0.05) higher in all the treated samples than control samples. However, in the frequency range from 0.01 to 100 Hz, there was not much difference between the control and treated sample in the frequency sweep test. The identified functional groups at different wavenumbers (cm−1) in the treated samples were found to be similar compared to the control samples.

Biocomposites from polyamide 11 reinforced by organic silane modified jute fibers: Fabrication and characterization

AbstractUsing plant derived polymers for the composite production has been considering as an efficiently attempt to reduce the impacts from the environmental pollution as well as utilizes the benefits they can bring. Fully jute/polyamide 11 (PA11) biocomposites are green materials expected to own many outstanding advantages of both components for example, high‐mechanical performances and especially environmentally friendliness. However, to the best of our knowledge, these materials has not been studied so far. This work focuses on the further modification of alkaline pre‐treated jute fibers by using vinyltrimethoxysilane (VTMS) and evaluates the effect of silanization on the interaction and adhesion between jute fibers and PA11 resin as well as the characteristics of resulting composites. By using Fourier transform infrared, thermogravimetry, mechanical property analysis, color difference measurement, and scanning electron microscopy observations, the contribution of VTMS modification to the enhancement on the interfacial interaction and adhesion between fibers and PA11 resin proved clearly. The results showed that tensile strength, impact strength; and Young's modulus of silanized jute biocomposites increased by 44.1; 26.5 and 55.6%, respectively in comparison to those of untreated fiber biocomposites. Similarly, thermal stability, resistance to water absorption and weathering resistance of obtained biocomposites were improved.

A new color distance measure formulated from the cooperation of the Euclidean and the vector angular differences for lidar point cloud segmentation

Two important features of the points in the LiDAR point clouds are the spatial and the color features. The spatial feature is mostly used in the point cloud processing field due to its 3D informative and distinctive characteristic. The local geometric difference derived from the spatial features of the points is usually benefited by graph-based point cloud segmentation methods, because the geometric features of the local point groups are highly distinctive. In this paper, we use both the geometric and color differences of the adjacent local point groups at the impact rates 0.3, 0.5, and 0.7 and cooperate the Euclidean and the vector color differences within several averaging techniques for the color difference. The difference forms have been tested within a graph-based segmentation method on four point cloud segmentation datasets, two indoor and two outdoor, using their spatial and color information. The geometric mean as an averaging techniques increases the segmentation success for the all datasets except one outdoor when the color differences are used in the segmentation at the impact rate 0.3, while the harmonic mean increases the success for the all datasets the successes except the other outdoor at the same impact rate. According to the test results, the cooperating of the Euclidean and vector angular color difference measurements can considerable increase the segmentation success on the point clouds with color information in a high quality.

Developing reliably distinguishable color schemes for legends of natural resource taxonomy-based maps

ABSTRACT The legends of natural resource taxonomy-based maps (e.g. soil, geological, geomorphological, vegetation, and land cover/land use) need many different distinguishable colors. The existing methods of color selection for map legends are based on the designer subjectivity, ensuring schemes having few colors. An analysis of the modeling and management of colors in digital applications has led to define an algorithm to calculate an objective colorimetric measure of color difference – “DE*ab ” – based on the perceptually uniform color model CIELAB. The proposed method consists of a set of specific rules for developing hierarchically structured color schemes and a specific procedure for ensuring selection of a large number of reliably distinguishable colors, based on a color difference threshold. The accuracy of color reproduction in printing processes is also taken into account. The method has been applied to develop a standard of colors for soil maps. It contains 63 colors and has been used for developing a soil map having 41 standard colors. A user test of the method results proved that thresholds of 10 DE*ab units and 15 DE*ab units ensure obtaining acceptably distinguishable colors for displaying/printing maps by using high-quality, respectively, current devices. Three datasets that support the research are given.

Comparison of Multilayer Transparent Wood and Single Layer Transparent Wood With the Same Thickness

In this paper, poplar was used as raw material, sodium chlorite was used to delignify it in acidic environment, and then epoxy resin was vacuum impregnated in the delignified wood template to prepare transparent wood. Moreover, in order to imitate the lamination method of plywood, the multilayer transparent wood was prepared by means of staggered vertical lamination. The purpose of this paper is to study the physical and chemical properties of multilayer transparent wood, and to explore the application potential of multilayer transparent wood as a new material by comparing with single layer transparent wood with the same thickness. The weight of wood components in the transparent wood prepared in this experiment accounts for about 30–45% of the weight of composite materials. Scanning electron microscopy (SEM) measurements, Fourier transform attenuated total reflection infrared spectroscopy (ATR-FTIR) characterization, weight gain measurements, UV transmittance measurements, color difference measurements, water contact angle measurements and mechanical properties measurements were used to study. The results showed that as the thickness of the transparent wood increased, the cracks between the resin and the wood cell wall increased, and the interface showed an uneven state. In the case of the same thickness, the multilayer transparent wood was made by laminating transparent wood sheets, with fewer internal cracks and smooth interfaces. Its light transmittance is better than single layer transparent wood. Moreover, compared with single layer transparent wood with the same thickness, the lightness of multilayer transparent wood decreased, and tended to yellow and red. Due to the removal of lignin, the tensile strength of transparent wood decreased during the preparation process. However, it can be seen from the mechanical strength test that the tensile strength of multilayer transparent wood is much higher than that of single layer transparent wood. To a certain extent, multilayer transparent wood can improve the mechanical strength of transparent wood. To conclude, multilayer transparent wood is a kind of natural transparent material with large thickness, good light transmission and excellent mechanical properties, and it has a good development prospect.

Towards improving the biocompatibility of prosthetic eyes

Prosthetic eyes are currently manufactured using Poly(methyl methacrylate) (PMMA) which is not an ideal material because it is hydrophobic. While significant research has investigated the benefits of hydrophilic materials for contact lenses, no such research has been carried out on hydrophilic materials for prosthetic eyes until now. In this study, different derivatives of Poly(ethylene glycol) (PEG) monomer and methyl methacrylate (MMA) monomer were grafted to PMMA using copolymerisation. The resulting matrixes were evaluated by water contact angle measurement, 24 h water absorption testing, and colour-difference measurement when exposed to ultraviolet light. The contact angle and water absorption results indicated that ethylene glycol dimethacrylate (EGDMA) grafted PMMA matrix had a better hydrophilic performance than the other matrixes tested. EGDMA is already a minor constituent of the PMMA matrix currently used for manufacturing prosthetic eyes but when the proportion of EGDMA monomer to MMA monomer used in the manufacturing process was increased to 50/50 the hydrophilicity of the matrix was significantly improved.EGDMA-grafted PMMA is inexpensive and comes as a liquid monomer that is easily mixed with the PMMA monomer that ocular prosthetists are familiar with. The mixture requires no special handling beyond the normal safety precautions that apply when using PMMA monomers. In-vitro testing shows that EGDMA-grafted PMMA significantly improves the wettability of PMMA currently used for the manufacture of prosthetic eyes and has the potential to significantly improve wearing comfort and socket health.

Preliminary Study of the Targeted Cleaning of an Artificial Gypsum Layer on White Marble

Targeting cleaning of the artificial gypsum layer on white marble was studied. It was conducted by means of the specific depletion of the calcium and sulfate ions by the barium carbonate scavenger, which led to the continuous dissolution and clearance of gypsum layer. The cleaning effect was evaluated by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), capillary suction, and color difference measurement. By this method, only the gypsum layer was cleared away and the carbonate substrate of marble was left intact at the same time. This method will be highly useful for the conservation of marble relics from surface weathering.

In-situ growth of calcium sulfate dihydrate as a consolidating material for the archaeological bones

Calcium sulfate dihydrate was grown in-situ on the bone relics as a consolidating material in this study. It was accomplished by introduction of the suspension liquid of nano calcium hydroxide in alcohol and the solution of ammonium sulfate in water on the surface of the bones successively. In the process, calcium hydroxide reacted with ammonium sulfate solution and a continuous phase of calcium sulfate dihydrate was formed. Due to the formation of the calcium sulfate dihydrate continuous phase, the integrity of the bone relics was reestablished and the strength of them was enhanced. The protective efficacy of this method was investigated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), microhardness, porosimetry and color difference measurement.

Robust HDR image quality assessment using combination of quality metrics

We propose a framework to combine various quality metrics using a full reference approach for High Dynamic Range (HDR) Image quality assessment (IQA). We combine scores from metrics exclusively designed for different applications such as HDR, Standard Dynamic Range (SDR) and color difference measures, in a non-linear manner using machine learning (ML) approaches with weights determined during an offline training process. We explore various ML techniques and find that support vector machine regression and gradient boosting regression trees are effective. To improve performance and reduce complexity, we use the back-tracking based Sequential Floating Forward Selection technique during training to include a subset of metrics from a list of quality metrics in our model. We evaluate the performance on five publicly available calibrated HDR databases with different types of distortion (including different types of compression, Gaussian noise, gamut mismatch, chromatic distortions and so on) and demonstrate improved performance using our method as compared to several existing IQA metrics. We perform extensive statistical analysis to demonstrate significant improvement over existing approaches and show the generality and robustness of our approach using cross-database validation.

Efficacy of alkyl ketene dimer modified microcrystalline cellulose in polypropylene matrix

In this study, microcrystalline cellulose (MCC), which is a completely bio-derived material, was modified. An alkyl ketene dimer was used for the modification. The improved performance is beneficial for polymer matrices and advantageous with regard to the color and oxygen permeability; thus, the produced composites can be widely used in industries. The objective of this study was to improve the performances of the polypropylene matrix. Composites were successfully prepared by adding modified MCC and MCC via an extrusion process. Subsequently, the properties of the composites were analyzed according to their compositions. To confirm the difference by modification, structural analyses and thermal-property measurements were conducted. The thermal and mechanical properties of the prepared composites were measured to investigate the effects of the MCC modification and the amount, and to determine the crystallinity. Additionally, oxygen-permeability and color-difference measurements were conducted to confirm that the composites would be suitable for industrial applications.

Spectrophotometric evaluation of pigmented urethane acrylate coating colour stability

The research was carried out testing two red pigment dispersion colour stability in UV light-curing urethane acrylate composition. The given urethane acrylate composition was pigmented with a pigment content of 0.1% to 5%. Coating colour change was evaluated at room temperature and at 50°C over a 28-day period. For all prepared pigment samples, spectrometric colour difference measurements were performed using CIEL*a*b* and CIEL*C*h* colour systems and FTIR-ATR to evaluate their stability over time. The colour stability was improved with increasing pigment concentration. There was found the difference between tested red pigments and can be concluded that one of them are more stable for use in pigmented coatings.

Strengths, Limitations, and Recommendations for Instrumental Color Measurement in Forensic Soil Characterization

Color determination of soil evidence is often done by visual comparison to soil color charts. A handheld spectrophotometer was tested with representative materials for its suitability for forensic soil characterization. Instrumental colorimetry provides accurate colorimetry with ~10-fold better precision than a soil color chart. The minimum sample size for accurate color determination was between 0.02 and 0.04mg of fine soil for the specific instrument tested. Reporting colors in the L*a*b* space permits quantification of ΔE00 , a measure of perceptible color difference, could enable objective quantification of small color differences and thresholds for forensic soil comparisons. A ΔE00 greater than ~ 3.5 to 6 likely indicates disparate soil sources in a forensic comparison, in the absence of confounding factors like sample alteration. Despite the superior precision of instrumental colorimetry, this approach is inappropriate for samples which are mottled at an inseparable scale, attached to a substrate, or too small for instrumental measurement.