CIELAB Color Space Research Articles

A feasible weave color scope inspection by using primary yarn colors to improve Jacquard reproduction quality

Producing a wide scope of weave colors is challenging in modern Jacquard weaving with limited weft color variety. The subtractive primary color yarns (cyan, magenta, yellow and black) are used to replicate varied Jacquard designs, but there is potential to improve the color reproduction quality by expanding a feasible weave color scope. Therefore, this research examined weave colors that are created by combining two sets of primary colors from different color systems. In color printing, six color pigments (i.e., cyan [C], magenta [M], yellow [Y], red [R], green [G] and blue [B]) are popularly used as primary colors for color reproduction. Therefore, weft yarn colors are selected in line with the six colors and a feasible weave color scope is inspected. The group of yarns is paired, and 225 weave color samples are produced to examine the color effects. The weave color samples are measured by a spectrophotometer and described by the CIELAB color space. The results show that the CIELAB color space was expanded by adding [R], [G] and [B] colored yarns. The hue and chroma ranges of the fabric samples were expanded compared with the fabrics produced by only [C], [M] and [Y] yarn colors. In this research, the possibilities in color reproduction are explored and the findings suggest great potential in producing a wide scope of weave colors by using primary yarn colors.

Genome-Wide Association Study and FST Analysis Reveal Four Quantitative Trait Loci and Six Candidate Genes for Meat Color in Pigs.

Meat color is the primary criterion by which consumers evaluate meat quality. However, there are a few candidate genes and molecular markers of meat color that were reported for pig molecular breeding. The purpose of the present study is to identify the candidate genes affecting meat color and provide the theoretical basis for meat color molecular breeding. A total of 306 Suhuai pigs were slaughtered, and meat color was evaluated at 45 min and 24 h after slaughter by CIELAB color space. All individuals were genotyped using GeneSeek GGP-Porcine 80K SNP BeadChip. The genomic estimated breeding values (GEBVs), heritability, and genetic correlation of meat color were calculated by DMU software. The genome-wide association studies (GWASs) and the fixation index (FST) tests were performed to identify SNPs related to meat color, and the candidate genes within 1 Mb upstream and downstream of significant SNPs were screened by functional enrichment analysis. The heritability of L* 45 min, L* 24 h, a* 45 min, a* 24 h, b* 45 min, and b* 24 h was 0.20, 0.16, 0.30, 0.13, 0.29, and 0.22, respectively. The genetic correlation between a* (a* 45 min and a* 24 h) and L* (L* 45 min and L* 24 h) is strong, whereas the genetic correlation between b* 45 min and b* 24 h is weak. Forty-nine significant SNPs associated with meat color were identified through GWAS and FST tests. Among these SNPs, 34 SNPs were associated with L* 45 min within a 5-Mb region on Sus scrofa chromosome 11 (SSC11); 22 SNPs were associated with a* 45 min within a 14.72-Mb region on SSC16; six SNPs were associated with b* 45 min within a 4.22-Mb region on SSC13; 11 SNPs were associated with b* 24 h within a 2.12-Mb region on SSC3. These regions did not overlap with meat color–associated QTLs reported previously. Moreover, six candidate genes (HOMER1, PIK3CG, PIK3CA, VCAN, FABP3, and FKBP1B), functionally related to muscle development, phosphatidylinositol phosphorylation, and lipid binding, were detected around these significant SNPs. Taken together, our results provide a set of potential molecular markers for the genetic improvement of meat color in pigs.

Influence of the Grain Size Distribution of the Limestone Additives on the Color Properties and Phase Composition of Sintered Ceramic Materials Based on Cream-Firing Clays.

The study focused on determining color changes in materials made of cream-firing clays from the Opoczno region (Poland) due to the addition of calcium carbonate in the form of limestone. Moreover, the influence of the grain size distribution of this additive on the color properties of the materials and their phase composition was determined. Test samples were prepared using theplastic method and fired at four different temperatures: 1120, 1140, 1160 and 1180 °C. The color properties of the surface of ceramic materials were determined in CIE-Lab color space using a colorimeter. Quantitative phase analysis was performed using the Rietveld method. The research showed that the addition of calcium carbonate causes an increase in the yellow color factor and a decrease in the red color factor and the brightness of the material. Moreover, it was proven that the grain size distribution of the additive used significantly influences the phase composition of the materials, thus determining the values of physical properties and the color of the materials.

Experimental Assessment of the Elastic Properties of Exocarp–Mesocarp and Beans of Coffea arabica L. var. Castillo Using Indentation Tests

The development of selective coffee harvesting technologies requires detailed knowledge of the geometrical, physical, and mechanical properties of the subsystems of the coffee bush, including the elastic properties of the substructures of fruit and the coffee bean, which are directly related to the selectivity problem. The elastic properties of the mesocarp–exocarp and bean are not described in the literature due to the difficulty of characterizing these locally, since measuring each component of the coffee fruit structure (mesocarp–exocarp and bean) is not an easy task. However, determining the elastic properties (of the mesocarp–exocarp and bean) could help create realistic simulations as an initial estimation for selective coffee harvesting studies. The present work aims to bridge the gap in the mechanical characterization of the sub-structures of the coffee fruits by assessing the elastic properties of the mesocarp–exocarp and bean. Indentation tests were performed on eighty Coffee arabica L. var. Castillo fruits and beans, which were previously classified into four ripening stages using fruit color data in the CIELab color space. Young’s modulus and indentation hardness of the mesocarp–exocarp structure and beans were calculated, applying the Oliver and Pharr indentation model and Hertz contact theory.

A method of tone reproduction curves computation by means of gradation trajectories in the form of Bézier curves

Tone reproduction curves (TRCs) have long been the basis for color adjustment in printing systems. Moreover, new algorithms for their processing and calculation, including tone value increase (TVI)‐based ones, are being constantly proposed. However, due to the fact that TRCs are just one‐dimensional curves covering only one colorant, they are not able to produce an exact match of all colors. Color adjustment with the help of the TRC is unstable, that is, a slight change in one color channel has a dramatic effect on the color reproduction in output. The use of gradation trajectories (GT) as an analytical model within the CIE Lab color space describing the behavior of the entire color gamut of the reproduction device makes it possible to more accurately adjust the individual color channel. Describing GT using the parametric Bézier curves further simplifies this process. In this work, we use GT to fit the TRC/TVI with the parameters recommended by ISO 12647‐2:2013.

A method to improve the color rendering accuracy in cultural heritage: preliminary results

Abstract Color specification is an important challenge in many application domains including Cultural Heritage. The collection of metadata concerning Cultural Heritage involves the valorization, fruition and becomes part of the conservation process. It becomes essential to find methods that simplify and optimize the acquisition of such data as color information. In this regard, in this work we present the preliminary results of a project that involves the acquisition by 3D scanner of samples of different colors placed in a controlled environment and with different illumination conditions. To make more accurate the color rendering, the color coordinates of each sample were measured by a spectrophotometer. All the obtained measurements become part of a dataset with which to train a machine learning model that learns how to perform the transformation from the RGB to the CIELab color space in different lighting condition.

Enhancing Moon Crescent Visibility Using Contrast-Limited Adaptive Histogram Equalization and Bilateral Filtering Techniques

Image enhancement is becoming increasingly important with the advancement of space exploration techniques and the technological development of more durable and scientifically sound observatories equipped with more powerful telescopes. The enhancement of images helps astronomers analyze the results and act toward determining the dates of religious festivals. This work describes a technique known as contrast-limited adaptive histogram equalization (CLAHE) with grayscale contrast enhancement and bilateral filtering. We apply CLAHE on the L component of the CIE-Lab color space to adjust lightness contrast. Subsequently, grayscale contrast enhancement is performed to increase the visibility of the moon crescent. Noise caused by grayscale contrast enhancement is reduced using bilateral filtering. Two quantitative measures are selected (PSNR and MSE) to show the visual improvement achieved by the proposed algorithm.

Effects of select copper sources at minimum supplementation levels on nutrient content, off-colors, and blemishes in canned pet food.

In the previous research, super-fortification with copper decreased vitamin E content and darkened canned pet food, which prevented the analysis of black blemishes reported in commercial products. The pet food industry has linked these blemishes, which may be concerning to pet owners, to copper supplementation. The objective of this study was to determine the effect of different copper sources included at minimum recommended levels on nutrient content, color, and blemishes in canned pet food. Treatments were arranged in a 2 × 3 + 1 factorial, with 2 levels of copper supplementation [6 and 12 mg/kg dry matter (DM)], 3 copper sources (CG = copper glutamate, CA = copper amino acid complex, and CS = copper sulfate), and a control with no added copper (NC). Diets were analyzed for macronutrients (moisture, crude protein, crude fat, crude fiber, and ash) and micronutrients (calcium, phosphorus, potassium, sodium, magnesium, sulfur, iron, copper, manganese, zinc, and vitamin E). Color was quantified with a CIELAB color space colorimeter wherein L* values closer to 100 represented lighter products and more positive a* and b* values indicated redder and yellower products, respectively. Blemishes were enumerated and their surface area quantified with ImageJ software. Data were analyzed as a general linear mixed model with the fixed effect of treatment and the random effect of production day. P-values less than 0.05 were considered significant. The 12 mg/kg DM treatments (average 14.19 mg/kg DM) contained the highest (P < 0.05) level of copper, followed by 6 mg/kg DM treatments (average 7.59 mg/kg DM) and then NC (0.00 mg/kg DM). Addition of copper decreased (P < 0.05) vitamin E content, except for NC and CS12 which were similar (P > 0.05; average 111.89 mg/kg DM). Lightness (average L* 63.66) was not affected (P > 0.05) by the treatments. Adding copper decreased (P < 0.05) redness, with higher (P < 0.05) a* values for CG6 (9.55) vs. CA6 and CS6 (average 8.50). Yellowness also decreased with the addition of copper, except for CG6 which was similar (P > 0.05) to NC (average 18.70). However, CG6 and CG12 (average 4.05 blemishes/slice of food) contained more (P < 0.05) blemishes than CA6, CS6, and CS12 (average 0.97 blemishes/slice of food). Minimal levels of supplemental copper from CG may enhance overall color preservation but could increase blemish occurrence. No disadvantage was observed for CA vs. CS, indicating that CA could be exchanged for CS in formulations.

A uniform illumination image enhancement via linear transformation in CIELAB color space

A uniform illumination image enhancement via linear transformation in CIELAB color space

Characteristics of Channel-Water in Blue-Green Beryl and Its Influence on Colour

This study reports the characteristics of water in channels of blue-green beryl and its effect on color. An industrial camera was used to measure color in the CIELAB color space. X-ray fluorescence (XRF), X-ray diffraction (XRD), infrared spectroscopy (IR), ultraviolet-visible (UV–vis) spectroscopy, and silicate rock chemical analysis method were used for analysis. The peaks at 5105 cm−1 and 5269 cm−1 were the combination tone of type II water, which were negatively correlated with b*, and positively correlated with the peak area at 3162 cm−1 (Na–H) and cell parameter a0. The peaks at 7097 cm−1 and 7142 cm−1 were related to the metal ions types in the channels. Part of the water in the channel combined with Fe3+ to form [Fe2(OH)4]2+ and cause a yellow tone, and when the yellow tone combined with the blue tone caused by Fe2+, the beryl has a blue-green colour.

Biodegradable Films of PLA/PPC and Curcumin as Packaging Materials and Smart Indicators of Food Spoilage.

Bio-based and biodegradable packaging combined with chemical sensors and indicators has attracted great attention as they can provide protection combined with information on the actual freshness of foodstuffs. In this study, we present an effective, biodegradable, mostly bio-sourced material ideal for sustainable packaging that can also be used as a smart indicator of ammonia (NH3) vapor and food spoilage. The developed material comprises a blend of poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) loaded with curcumin (CCM), which is fabricated via the scalable techniques of melt extrusion and compression molding. Due to the structural similarity of PLA and PPC, they exhibited good compatibility and formed hydrogen bonds within their blends, as proven by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis confirmed that the blends were thermally stable at the used processing temperature (180 °C) with minimal crystallinity. The rheological and mechanical properties of the PLA/PPC blends were easily tuned by changing the ratio of the biopolymers. Supplementing the PLA/PCC samples with CCM resulted in efficient absorption of UV radiation, yet the transparency of the films was preserved (T700 ∼ 68–84%). The investigation of CCM extract in ethanol with the DPPH• assay demonstrated that the samples could also provide effective antioxidant action, due to the tunable release of the CCM. Analyses for water vapor and oxygen permeability showed that the PPC improved the barrier properties of the PLA/PPC blends, while the presence of CCM did not hinder barrier performance. The capacity for real-time detection of NH3 vapor was quantified using the CIELab color space analysis. A change in color of the sample from a yellowish shade to red was observed by the naked eye. Finally, a film of PLA/PPC/CCM was successfully applied as a sticker indicator to monitor the spoilage of shrimps over time, demonstrating an evident color change from yellow to light orange, particularly for the PPC-containing blend. The developed system, therefore, has the potential to serve as a cost-effective, easy-to-use, nondestructive, smart indicator for food packaging, as well as a means for NH3 gas monitoring in industrial and environmental applications.

Non-destructive follow-up of ‘Jintao’ kiwifruit ripening through VIS-NIR spectroscopy – individual vs. average calibration model’s predictions

Visible/near infrared spectroscopy (Vis-NIRS) was used to monitor the yellow-fleshed kiwifruit (Actinidia chinensis Planch ‘Jintao’) ripening on two selected orchards along 13 weeks, from pre-harvest to the late harvest. Calibration models for several Internal Quality Attibutes (IQA) were built from the spectral data of 375 individual kiwifruit. The analyzed IQA were L*, a* and b* from the CIELAB color space, hue angle, chroma, firmness, dry matter (DM), soluble solids content (SSC), juice pH and titratable acidity (TA). Different pre-processing methods were tested for the construction of PLS calibration models. SSC and Hue were the best performing models with a correlation coefficient of 0.81 and 0.88, and root mean square error of prediction (RMSEP) of 1.27% and 1.95∘, respectively. The interpretation of the models in terms of the known absorption bands and the impact of signal to noise ratio (SNR) in them is discussed. The calibration models were used to perform average predictions of the IQA on orchard subareas, for each day of the experiment. These average predictions were compared with the IQA’s average reference values on the same subareas and days. The model’s metrics improved significantly through the averaging procedure, with RMSEP = 0.26–0.36% and R2 = 0.99 for SSC; and RMSEP = 0.42∘ – 0.56∘ and R2 ≈ 1 for Hue. Since orchard management is done essentially through averages and not individual values, this result reinforces the applicability of the NIR technology for follow-up of fruit ripening in the tree.

Oil From Three Aguaje Morphotypes (Mauritia flexuosa L.f.) Extracted by Supercritical Fluid With CO2: Chemical Composition and Chromatic Properties

The chemical composition and CIELAB color parameters of oil from three aguaje morphotypes (Mauritia flexuosa L.f.) extracted by supercritical carbon dioxide was investigated. By chromatography (HPLC and GC), spectrometry (UV/vis), and digital image colorimetry (digital camera), carotenoids, tocopherols, tocotrienols, fatty acids, total polyphenols, and CIELAB color space were analyzed. These findings showed that the oil obtained from morphotype 3 was superior in several analytes (carotenoids, polyphenols, oleic acid, β-sitosterol, campesterol, and stigmasterol), while morphotype 2 and morphotype 1 showed very close profiles. The most similar chemical components in the oils of the three morphotypes were stigmasterol (16.00 to 17.81%), β-sitosterol (66.39 to 68.94%), palmitic acid (15.56 to 20.69%), and oleic acid (73.29 to 79.54%). The chromatic parameters (L*, a*, b*, and Cab*) were quite different except for the hue angle (hab) (66.55 to 69.71 U), which showed some similarity. Aguaje oil is an interesting resource that stands out for its high content of carotenoids. All three morphotypes may be suitable for potential commercial applications.

Perceptually Optimal Color Representation of Fully Polarimetric SAR Imagery.

The four bands of fully polarimetric SAR data convey scattering characteristics of the Earth’s background, but perceptually are not very easy for an observer to use. In this work, the four different channels of fully polarimetric SAR images, namely HH, HV, VH, and VV, are combined so that a color image of the Earth’s background is derived that is perceptually excellent for the human eye and at the same time provides accurate information regarding the scattering mechanisms in each pixel. Most of the elementary scattering mechanisms are related to specific color and land cover types. The innovative nature of the proposed approach is due to the two different consecutive coloring procedures. The first one is a fusion procedure that moves all the information contained in the four polarimetric channels into three derived RGB bands. This is achieved by means of Cholesky decomposition and brings to the RGB output the correlation properties of a natural color image. The second procedure moves the color information of the RGB image to the CIELab color space, which is perceptually uniform. The color information is then evenly distributed by means of color equalization in the CIELab color space. After that, the inverse procedure to obtain the final RGB image is performed. These two procedures bring the PolSAR information regarding the scattering mechanisms on the Earth’s surface onto a meaningful color image, the appearance of which is close to Google Earth maps. Simultaneously, they give better color correspondence to various land cover types compared with existing SAR color representation methods.

Alizarin-functionalized organic-inorganic silane coatings for the development of wearable textile sensors

HypothesisThe broad detection properties of alizarin, not only concerning pH variations but also temperature, glucose and health-like relevant cations alterations, make it a molecule of great scientific interest, particularly for developing multifunctional wearable sensors. ExperimentHerein, the alizarin red S dyestuff is bonded with trimethoxy-[3-(oxiran-2-ylmethoxy)propyl]silane, as a sol–gel precursor, to functionalize cotton fabrics. The chemical and structural properties of both plain and silane-functionalized dyestuffs are investigated in solution and solid-state by several chemical-physical characterization techniques. FindingsThe hybrid dyestuff characterization reveals the epoxy ring-opening of the silica precursor, leading to covalent linkages to the sulfonic group of alizarin, which retains its structure during the sol–gel reaction. The silane-functionalized halochromic dyestuff shows similar halochromic behaviour as its pristine solution in the investigated pH range, thus demonstrating a color shift from yellow to red due to the protonation/deprotonation reversible mechanism of the chromophore. The reversibility and repeatability of pH-sensing properties of treated cotton fabrics are confirmed by diffuse reflectance and CIELAB color space characterizations. Cotton fabric functionalized with alizarin-containing sol–gel coating shows excellent durability of halochromic properties, thus emerging as a versatile platform for stimuli-responsive materials.

Effect of astaxanthin and spirulina levels in black soldier fly larvae meal-based diets on growth performance and skin pigmentation in discus fish, Symphysodon sp.

This study was conducted to evaluate the effects of spirulina levels and 100 mg kg−1 astaxanthin supplementation in the diets replaced with 50% of fishmeal by black soldier fly larvae (BSFL) on growth performance, survival rate (SR) and skin color of discus fish Symphysodon sp.. Fish were randomly distributed into 18 tanks at 10 fish/tank for each of the 6 experimental diets, treatments of which consisted of frozen beef-heart (T1), commercial feed for discus fish (T2), with the remaining four diets being supplemented with dried spirulina at 0 g (T3), 3 g (T4), 6 g (T5) and 9 g kg−1 feed (T6) and 100 mg kg−1 astaxanthin for 10 weeks. Fish fed the frozen beef-heart treatment had the highest growth rate and lowest FCR that differed significantly from the other treatments (p < 0.05). After the 10-week trial, skin color intensity from four locations on the fish evaluated using the CIE LAB color space method. There was an increasing trend for the L* value (brightness) at the four positions on the body from T1 to T6; particularly, increasing spirulina levels in the diets increased brightness. The lowest color value a* (redness) at all points were found in the T1 and T2 treatments and differed significantly from the other diets supplemented with 100 mg kg−1 astaxanthin (T3–T6) (p < 0.05). There was an increasing trend in the color value b* (yellowness) from the four locations on the body when spirulina levels were increased in the diets. In conclusion, the diets for those that replaced 50% of fishmeal by BSFL and supplemented with astaxanthin and spirulina enhanced the SR and color intensity of the fish body but had no effect on growth performance.

Human perception of color differences using computer vision system measurements of raw pork loin

In the food industry, product color plays an important role in influencing consumer choices. Yet, there remains little research on the human ability to perceive differences in product color; therefore, preference testing is subjective rather than based on quantitative colors. Using a de-centralized computer-aided systematic discrimination testing method, we ascertain consumers' ability to discern between systematically varied colors. As a case study, the colors represent the color variability of fresh pork as measured by a computer vision system. Our results indicate that a total color difference (ΔE) of approximately 1 is discriminable by consumers. Furthermore, we ascertain that a change in color along the b*-axis (yellowness) in CIELAB color space is most discernable, followed by the a*-axis (redness) and then the L*-axis (lightness). As developed, our web-based discrimination testing approach allows for large scale evaluation of human color perception, while these quantitative findings on meat color discrimination are of value for future research on consumer preferences of meat color and beyond.

Fabricating a photochromic material into a cellulose film for UV sensing and photo-patterning

Photochromic materials are widely applied in many fields, but their applications are partly limited by the complexity in both synthesis and device-fabrication, as well as the difficulty in quantitative analysis. We developed a photochromic compound (DHAIA) capable of changing color and fluorescence upon UV radiation. The change can be quantitatively analyzed via CIELAB color space, further yielding color shift (ΔELab) values that can be either recognized by instruments or detected by naked eyes. The compound can be fabricated into a photo-responsive film to serve as a sensitive UV sensor, allowing a low detection limit down to 20 μW/cm2 (UV radiation intensity). In addition, a photo-patterning technique was demonstrated, wherein patterns can be printed using either UV light or sunlight.

What’s next in the use of opacifiers for cosmetic coatings of solid dosage forms? Insights on current titanium dioxide alternatives

The consolidated use of coatings containing E171 (i.e. titanium dioxide, TiO2) as an opacifier has made the white color of the resulting dosage forms a quality standard in the pharmaceutical and dietary supplement fields. This color is also associated with the efficiency of the coating layer in protecting the substrate from the effects of UV rays. However, health risks related to diet exposure to TiO2 has recently been advanced and its addition in coating formulations has been seriously questioned. As a consequence, in principle safer TiO2-free formulations have been recently launched on the market, especially for coatings of dietary supplements. In this work, we evaluated the overall physico-technological characteristics and performance of immediate release tablets coated with a variety of commercial cosmetic formulations free of E171. Moreover, a quantitative method based on the CIELab color space was proposed for the first time for studying the covering/coloring performance of the coating formulations. Based on the results obtained, the possibility to achieve a satisfactory covering capability and a degree of white comparable to that of a standard TiO2-containing reference with all the commercially-available ready-to-use TiO2-free products considered, without affecting the dissolution performance, was demonstrated.

Color inconstancy in CIELAB: A red herring?

AbstractColor constancy is something we take for granted. An apple appears red despite monumental changes in the intensity and spectral balance of illumination. There are many components to the human visual system that make this illusion possible. Nonetheless, the system is imperfect. Objects will change apparent color under different illumination. The CIELAB color space allows for the computation of color values under any illuminant. CIELAB values will, in general, change as the illuminant changes. It would be natural to assume that these changes in CIELAB values would agree with the apparent color change that a human would experience. But the chromatic adaptation built into CIELAB is known to be less than optimal due to an imperfect emulation of how the adaptation process is performed in the human visual system. As a result, at least part of the illuminant color change implied by the CIELAB values is an artifact of this imperfect emulation. This paper investigates the magnitude of this artifact by comparing color changes implied by CIELAB with color changes in a color system that mimics CIELAB, except that it more closely emulates the human visual system. The difference between the two estimates of color change is assumed to be an artifact of CIELAB's poor emulation of the chromatic adaptation process. As color manufacturers are dealing with a wider spectrum of illumination sources, they may wish to consider the issue of color constancy; what colors and what formulations of colors exhibit better color constancy? Can CIELAB be used to quantify this? Or are color spaces that are based on LMS rather than XYZ more appropriate?