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The CIELAB color space diagram. The CIELAB, or CIE L* a* b*, color system represents quantitative relationship of colors on three axes: L* value indicates lightness, and a* and b* are chromaticity coordinates. On the color space diagram, L* is represented on a vertical axis with values from 0 (black) to 100 (white). The a* value indicates red-green component of a color, where þa* (positive) and Àa* (negative) indicate red and green values, respectively. The yellow and blue components are represented on the b* axis as þb* (positive) and Àb* (negative) values, respectively. At the center of the plane is neutral or achromatic. The distance from the central axis represents the chroma (C*), or saturation of the color. The angle on the chromaticity axes represents the hue (h o ). The L*, a*, and b* values can be transcribed to dermatological parameters. The L* value correlates with the level of pigmentation of the skin. The a* value correlates with erythema. The b* value correlates with pigmentation and tanning. CIE, Commission Internationale de l'Eclairage.

The CIELAB color space diagram. The CIELAB, or CIE L* a* b*, color system represents quantitative relationship of colors on three axes: L* value indicates lightness, and a* and b* are chromaticity coordinates. On the color space diagram, L* is represented on a vertical axis with values from 0 (black) to 100 (white). The a* value indicates red-green component of a color, where þa* (positive) and Àa* (negative) indicate red and green values, respectively. The yellow and blue components are represented on the b* axis as þb* (positive) and Àb* (negative) values, respectively. At the center of the plane is neutral or achromatic. The distance from the central axis represents the chroma (C*), or saturation of the color. The angle on the chromaticity axes represents the hue (h o ). The L*, a*, and b* values can be transcribed to dermatological parameters. The L* value correlates with the level of pigmentation of the skin. The a* value correlates with erythema. The b* value correlates with pigmentation and tanning. CIE, Commission Internationale de l'Eclairage.

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Skin color evaluation contributes to assessment of an individual's cutaneous phenotype. Skin color changes provide important clues to disease progression or treatment response. Skin color is also a predictor of skin cancer risk. Melanin pigment, blood flow, skin thickness, and photoaging contribute to skin color. Melanin, hemoglobin, bilirubin, and...

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... 1976 CIELAB measurements are found to correlate to skin color and related parameters, such as erythema (Brainard and Stockman, 2010;Del Bino and Bernerd, 2013;Everett et al., 2012). The CIELAB, or CIE L* a* b*, system is a threedimensional color-space consisting of three axes ( Figure 1). The L* axis is a gray scale with values from 0 (black) to 100 (white). ...

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... The analysis was performed on flowers lying on an area of approximately 24 cm 2 and each sample was analyzed in triplicate. The color was defined on the base of the chromatic coordinates [19], lightness (L*), green-red (a*) and blue-yellow components (b*). The Chroma value C*, which is an expression of color saturation, was also used to evaluate the color, and calculated by the relation: ...
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Edible flowers (EFs) are currently consumed as fresh products, but their shelf life can be extended by a suitable drying technique, avoiding the loss of visual quality and valuable nutraceutical properties. Begonia cucullata Willd is a common ornamental bedding plant, and its leaves and flowers are edible. In this work, B. cucullata red flowers were freeze-dried (FD) and hot-air dried (HAD) at different temperatures. To the best of our knowledge, our study is the first one comparing different drying methodologies and different temperatures involving sensory characterization of EFs; therefore, a codified method for the description of the sensory profile of both fresh and dried B. cucullata was developed and validated. Phytochemical analyses highlighted the better preservation of antioxidant compounds (polyphenols, flavonoids and anthocyanins) for flowers dried at 60–70 °C. Visual quality was strongly affected by the drying treatments; in particular the color of the HAD samples significantly turned darker, whereas the FD samples exhibited a marked loss of pigmentation. Although all drying conditions led to a reduction in the hedonic indices if compared with fresh flowers, the best results in terms of organoleptic properties were obtained when the drying temperature was set to 60 or 70 °C.
... Consistent and reproducible color assessment is one of the most useful techniques in dermatology. Devices used for this purpose can quantify color, erythema, and tan in various skin types; the devices contain a spectrophotometer that analyzes the spectral characteristics of a color [53]. This technique is currently used due to its non-invasive nature and allows the characterization of injured skin from non-injured skin in patients with skin involvement; it is also used to evaluate the efficacy of drugs on skin pigmentation [54]. ...
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The poor water solubility of apremilast (APR) is the main impediment to the penetration of the drug through the skin barrier. The objective of this study was to evaluate the permeability of APR in different solutions enriched with penetration promoters in ex vivo samples of human skin, and additionally assess its tolerance in vivo. To this end, APR solutions with 5% promoter were developed, and the drug’s ability to penetrate human abdominal skin samples was evaluated; the coefficients of permeability, cumulated amounts permeated, and flow were some of the parameters evaluated; likewise, the in vitro and in vivo tolerance of the solutions was evaluated. The results obtained showed that the solutions containing squalene as a promoter improved the penetration of APR compared to the other promoters evaluated; in the same way, on an in vitro scale in HaCaT cells, the promoters were not toxic, finding a cell viability greater than 80% at the different dilutions evaluated. In the in vivo tests carried out with the solution that presented the best results (APR-Squalene solution), it was observed that it does not cause irritation or erythema on the skin after its colorimetric and histological evaluation of the dorsal region of rats after its application. Squalene becomes an excellent candidate to improve the permeability of the drug in the case of the development of a topical formulation; in addition, it was confirmed that this penetration enhancer is neither toxic nor irritating when in contact with the skin in in vivo tests.
... Skin color is a major area of study in dermatology, and more broadly, renewed emphasis has recently been placed on identifying disparities in accuracy of clinical technologies such as pulse oximeters among patients with different skin tones. [1][2][3][4] Pigmentation elements, such as melanin, hemoglobin, and carotenoids, selectively absorb light at specific wavelengths; the remainder of the light can be scattered back to the surface to be detected by the eye as a "skin color." This detected "color" is a combination of the spectrum of the incident light, the specular and diffuse reflectance of the tissue, and the spectral response of the eye. ...
... The use of skin colorimetry has been common for the past 50 years to characterize reactivity of normal skin to light (e.g., tanning and erythema) and to diagnose and monitor conditions, such as port-wine stain and skin cancer. 2 In dermatology, tristimulus colorimeters collect reflectance data within the visible spectrum and use the International Commission on Illumination (CIE) L à a à bà color space for quantitative skin color classification. 5,6 Here, Là is used to describe lightness, aà is the green to red component, and bà is the blue to yellow component. ...
Article
Significance: Spatial frequency domain imaging (SFDI) is a wide-field diffuse optical imaging technique for separately quantifying tissue reduced scattering (μs ' ) and absorption (μa) coefficients at multiple wavelengths, providing wide potential utility for clinical applications such as burn wound characterization and cancer detection. However, measured μs ' and μa can be confounded by absorption from melanin in patients with highly pigmented skin. This issue arises because epidermal melanin is highly absorbing for visible wavelengths and standard homogeneous light-tissue interaction models do not properly account for this complexity. Tristimulus colorimetry (which quantifies pigmentation using the L * "lightness" parameter) can provide a point of comparison between μa, μs ' , and skin pigmentation. Aim: We systematically compare SFDI and colorimetry parameters to quantify confounding effects of pigmentation on measured skin μs ' and μa. We assess the correlation between SFDI and colorimetry parameters as a function of wavelength. Approach: μs ' and μa from the palm and ventral forearm were measured for 15 healthy subjects with a wide range of skin pigmentation levels (Fitzpatrick types I to VI) using a Reflect RS® (Modulim, Inc., Irvine, California) SFDI instrument (eight wavelengths, 471 to 851 nm). L * was measured using a Chroma Meter CR-400 (Konica Minolta Sensing, Inc., Tokyo). Linear correlation coefficients were calculated between L * and μs ' and between L * and μa at all wavelengths. Results: For the ventral forearm, strong linear correlations between measured L * and μs ' values were observed at shorter wavelengths (R > 0.92 at ≤659 nm), where absorption from melanin confounded the measured μs ' . These correlations were weaker for the palm (R < 0.59 at ≤659 nm), which has less melanin than the forearm. Similar relationships were observed between L * and μa. Conclusions: We quantified the effects of epidermal melanin on skin μs ' and μa measured with SFDI. This information may help characterize and correct pigmentation-related inaccuracies in SFDI skin measurements.
... Colorimetry was used to evaluate the luminance (L*) value to obtain a non-biased element of the reflection coefficient of genital pigmentation, and patients with distinctions greater than 2 between the adjoining skin and the genital area were excluded. 16 Inclusion criteria enrolled general healthy females aged 18-40, sexually active. Not using previous known topical, physical, systemic, or surgical treatment in the tested area in the previous six weeks; exclusion criteria included pregnancy, nursing, menopause, obesity, acquired acanthosis nigricans, or a systemic pigmentary disorder. ...
... A tristimulus colorimeter was utilized to accurately assess skin pigmentation changes (Chromameter CR-300, Minolta). 16 L*(luminosity), where 100 equals the complete white and 0 equals the complete black, was used to examine the change in color. Redness was measured on the A*axis on a ranging from 0 to 50. ...
Article
Background: Cyperus Rotundus Essential Oil (CREO) is an anti-inflammatory and depigmenting agent that helps treat hyperpigmentation. Objectives: The purpose of this study was to evaluate the depigmenting effect of CREO on genital hyperpigmentation to that of arbutin (ARB), as well as to evaluate the association between genital lightening, genital self-image, sexual performance, and life quality. Material and methods: Three hundred and eight healthy people were categorized into 3 groups: the CREO group, the ARB group, and the cold cream group (CC). In genital pigmentation, the tristimulus colorimeter is used to assess erythema and pigmentation. Additionally, we aided in the development of the female genital self-image scale (FGSIS-4), the female sexual function index (FSFI), and the dermatology life quality index (DLQI). Result: The reduction in genital hyperpigmentation was significantly greater in the CREO and ARB groups than in the CC group; in physician global assessment and patients' self-assessment, the results in treated bikini with the CREO and ARB groups were excellent when compared to the CC. Furthermore, no adverse effects were found in the CREO group, but mild irritation was found in the ARB group; additionally, the percentage of hair growth, color and luminance reduction, and hair thickness were significantly reduced in the CREO group only. In addition, there were significantly different in FGSIS, FSFI, and DLQI between the CREO and ARB groups and the CC group. Conclusion: CREO is equivalently efficacious in decreasing pigmentation, inflammation, and hair growth in the genital area. Positive changes boost female genital self-image, self-esteem, and sexual performance. Improving sexual health has a positive impact on quality of life.
... The chrominance components have a more significant dynamic range than the red, green, and blue channels in RGB color space [19]. In addition, it correlates with skin color and related parameters and describes better the subtle changes occurring in them [44]. ...
Preprint
Photoplethysmography (PPG) signals have become a key technology in many fields such as medicine, well-being, or sports. Our work proposes a set of pipelines to extract remote PPG signals (rPPG) from the face, robustly, reliably, and in a configurable manner. We identify and evaluate the possible choices in the critical steps of unsupervised rPPG methodologies. We evaluate a state-of-the-art processing pipeline in six different datasets, incorporating important corrections in the methodology that ensure reproducible and fair comparisons. In addition, we extend the pipeline by proposing three novel ideas; 1) a new method to stabilize the detected face based on a rigid mesh normalization; 2) a new method to dynamically select the different regions in the face that provide the best raw signals, and 3) a new RGB to rPPG transformation method called Orthogonal Matrix Image Transformation (OMIT) based on QR decomposition, that increases robustness against compression artifacts. We show that all three changes introduce noticeable improvements in retrieving rPPG signals from faces, obtaining state-of-the-art results compared with unsupervised, non-learning-based methodologies, and in some databases, very close to supervised, learning-based methods. We perform a comparative study to quantify the contribution of each proposed idea. In addition, we depict a series of observations that could help in future implementations.
... The a* value is relative to the green-red colors, with negative values toward green and positive values toward red. The b* axis represents the blue-yellow, with negative values toward blue and positive toward yellow [58]. The Table 1 shows that the luminosity (L*) parameter resented a range of values of 85.6 to 13.8. ...
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The high susceptibility to deterioration and diseases during the supply chain and/or during the storage of fresh products is a problem in the industry, and edible films are proposed as efficient methods to preserve its quality. The objective was to obtain and characterize silver nanoparticles (AgNPs) and determine their effect on optical, barrier and mechanical properties of alginate-based films. The alginate was extracted from Sargassum fluitans. AgNPs were obtained by green synthesis using Gliricidia sepium. The UV–Vis and dynamic light scattering (DLS) were used to characterize the AgNPs. The antifungal activity of AgNPs was investigated using several fungal strains. Films were formulated by using 2 and 3% alginate, as well as 0, 1, and 2 mg of AgNPs per mL of formulation, with glycerol as a plasticizer. A randomized experimental design was used to test the effect to alginate and the AgNPs concentrations. The results were analyzed by an ANOVA test (p < 0.05). The films were characterized by water vapor permeability (WVP), mechanical properties, opacity, color, glass transition and melting temperatures, as well as scanning electron microscopy (SEM) and energy dispersive X-Ray (EDS) spectroscopy. WVP, optical and mechanical properties of the films were influenced statistically with alginate and AgNPs concentrations. The PVA values varied between 0.83 and 1.74 g mm h−1 kPa−1 m−2. The results demonstrated that films made with higher alginate and AgNPs concentrations exhibited higher tensile strength (20.35 MPa) and elongation at break (74.56%). The AgNPs showed percentages of growth inhibition higher than 79% in all fungal strains tested. The films formulated had attractive properties that are used to extend shelf life of foods.
... The b 0 axis is the yellow-blue colour axis. Positive value are definitions that represent values associated with the colour yellow, and negative values associated with the colour blue (Ly et al., 2020). Originally defined by the CAE and specified by the CIE (Bora et al., 2015). ...
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Purpose-In this present study, electrophotographic printing is made on papers which are subjected to different recycling numbers, and this paper aims to examine the colour changes of this printing type. Design/methodology/approach-Four-colour electrophotographic printing is carried out on adhering to the INGEDE 11p standard recycled papers four times under the same conditions. Colour measurements are made by means of electrophotographic printed colour scales printed on these recycled papers. Colour measurements are made with the X-Rite eXact spectrophotometer according to the ISO 13655:2017 standard. As a result of colour measurements, colour differences (DL 0 , DH 0 , DC 0 , DE 00) of recycled papers are determined using some formulas. Findings-According to the values obtained after four recycling, the highest DL 0 value is found to be 4.80 yellow and the lowest 1.92 black. Again, according to the measurement results, it is determined that the highest DE00 is yellow colour with a value of 5.66, and lowest DE 00 is black colour with a value of 1.98. In DH 0 , black colour is the highest value of 12.61, the lowest value with À2.05 is obtained in magenta colour. It was observed that the highest DC 0 value is 2.98 in yellow, and the lowest value is À0.28 in black. Originality/value-In the printing industry, sometimes customers want to monitor the colour differences in the printing by taking the L 0 a 0 b 0 obtained values as a result of printing from the printing houses. If the colour differences exceed the tolerance values, then they can interfere with the printing. As a result of the calculations, colour changes in electrophotographic printing are observed with many parameters. This study can be a pioneer for the studies that can be done on this subject.
... Additionally, both degradation processes led to the formatio When evaluating the surface of polymeric materials, the Euclidean distance (∆E) is often used. ∆E describes the quantitative relationship of the colors shown in Figure 6 [25], and its values are computed by formula (2). In the range 0 < ∆E < 1, there is no difference in color change. ...
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Biodegradable polymer materials are increasingly used in the packaging industry due to their good properties and low environmental impact. Therefore, the work was performed on the injection molding of the bio-based composites of polylactide (PLA) and polyhydroxyalcanates (PHI) modified with two phases: reinforcing (walnut shell flour and cellulose) and coloring (beta carotene and anthocyanin). The produced materials were subjected to wide mechanical characteristics—tensile, flexural, and fatigue tests. Additionally, the influence of photo and hydrodegradation on the change of the surface structure and mechanical properties of the composites was assessed. The addition of natural fillers contributed to the improvement of the stiffness of the tested composites. PHI composites withstood a higher number of cycles during cyclic loading, but the stress values obtained in the static tensile test were higher for PLA composites. Moreover, a clear change of color was observed after both the photo and hydrodegradation process for all tested materials; however, after the degradation processes, the filler-modified materials underwent greater discoloration. For the composites based on PHI, the type of degradation did not affect the mechanical properties. On the other hand, for PLA composites, hydrolytic degradation contributed to a higher decrease in properties—the decrease in tensile strength for unmodified PLA after photodegradation was 4%, while after hydrodegradation it was 24%.
... Evaluating coloration changes using a spectrophotometer is necessary to assess the success of therapy in pigmentation disorders. 12 Three parameters are assessed objectively in spectrophotometer examination, namely L* (luminance: black and white) to assess the level of skin brightness, a* (green and red) to assess erythema which will increase if erythema occurs, and b* (blue and yellow) to assess hyperpigmentation disorders. 12,13 Spectrophotometric examination on this patient revealed brightening of the skin with an increased L* value and fading redness with a reduced a* value. ...
... 12 Three parameters are assessed objectively in spectrophotometer examination, namely L* (luminance: black and white) to assess the level of skin brightness, a* (green and red) to assess erythema which will increase if erythema occurs, and b* (blue and yellow) to assess hyperpigmentation disorders. 12,13 Spectrophotometric examination on this patient revealed brightening of the skin with an increased L* value and fading redness with a reduced a* value. The L* value was increased from 52.33 to 55.45, from 36.68 to 40.81, and from 52.36 to 56.42 on the right side, left side, and middle part of the nose, respectively, whereas the a* value was decreased from 15.55 to 14.21, from 13.08 to 10.07, and from 16.41 to 13.39 on the right side, left side, and middle part of the nose, respectively. ...
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Rhinophyma is characterized by progressive enlargement of the nasal skin, which is considered to be an advanced stage of phymatous rosacea. Esthetic disfigurement makes surgical treatment necessary for this condition. Hypertrophic scars are the consequence of alterations in the skin's healing process following surgical interventions. Laser may be the treatment of choice in hypertrophic scars. We reported a case of hypertrophic scars following excisional surgery and full-thickness skin grafting due to rhinophyma in an 18-year-old male who was consulted from the Department of Plastic Surgery and Reconstruction. The 1064 nanometer (nm) Q-switched Neodymium: Yttrium Aluminum Garnet (QS Nd:YAG) with 4 mm spot size, 1.5 J/cm2 and 1 Hz was applied to the hypertrophic scars for three sessions within one month interval. Clinical improvement was observed as indicated by the patient's Vancouver scar scale score and spectrophotometry result, and no side effects were found. Nd:YAG laser is a non-ablative device that targets hemoglobin, water, and melanin. Any thermal effects on dermal tissue containing blood vessels could result in reduced blood flow through the capillaries in the dermal papillae. QS Nd:YAG-induced selective photothermolysis was responsible for collagen breakdown and reduced collagen production in hypertrophic scars. The 1064 nm QS Nd:YAG laser gave good results in this case although more treatment sessions may be recommended and a longer follow-up is necessary in order to assess the stability of the result.
... According to Chaudhari et al. [11], the threshold of RGB images cannot be used to accurately identify the spot of disease from brown infected rice leaves and the entry on the 'H' component of the HSI colour model and 'Cr' component of YCbCrcolour model [12] sometimes identified as disease spots but not in all. However, the threshold on the' component of the CIELAB [13]colour model allowed accurate detection of disease spots and is independent of background effects. ...
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Considering the human population, food is one of the major problems Sri Lanka might face in the near future. Rice is the most widely consumed food product and one of the extensively cultivated crops in Sri Lanka. Therefore, increasing the crop yield is one of the primary needs of the country. When rice crops are infected with diseases, it results in a loss of crops. Therefore, it is essential to identify the disease in the early stage of infection to prevent the damage that can be done. Disease identification could be challenging without a clear understanding. With the advancement of new technologies, researchers are interested in identifying paddy diseases through machine learning and image processing techniques to help farmers identify infectious diseases accurately. It is difficult to observe the paddy leaf with the naked eye to diagnose the infected disease. In this research, an algorithm was developed to check whether the image contains different changes to the paddy leaf by considering the green colour pixels and their variance. OpenCV libraries have been used to develop the algorithm for feature extraction. Those features were used as attributes to the LightGBM algorithm to classify the disease images with over 80% accuracy.