Color Matching Technique Research Articles

Estimating Surface Concentrations of Calanus finmarchicus Using Standardised Satellite-Derived Enhanced RGB Imagery

Calanus finmarchicus is a keystone zooplankton species that is commercially harvested and is critical in sustaining many important fisheries in the North Atlantic. However, due to their patchy population distributions, they are notoriously difficult to map using traditional ship-based techniques. This study involves the use of a combined approach of standardized ocean colour imagery and radiative transfer modelling to identify reflectance anomalies potentially caused by surface swarms of C. finmarchicus in the northern Norwegian Sea. Here, we have standardized satellite eRGB imagery that depicts a distinct ‘red’ patch, which coincides with in situ measurements of high surface concentrations of C. finmarchicus. Anomaly mapping using a novel colour matching technique shows a high degree of anomaly within this patch compared to the surrounding waters, indicating the presence of something other than the standard bio-optical model constituents influencing the optics of the water column. Optical closure between modelled and satellite-derived reflectance signals is achieved (and the anomaly is significantly reduced) through the addition of C. finmarchicus absorption into the model. Estimations of the surface concentrations of C. finmarchicus suggest between 80,000 and 150,000 individuals m−3 within the extent of the identified red patch. Furthermore, analysis of the impact of C. finmarchicus absorption on the OC3M algorithm performance points to the potential for the algorithm to over-estimate chlorophyll concentrations if C. finmarchicus populations are present in the surface waters.

Non-invasive study of the dyes and pigments in the Chinese woodblock New Year paintings

Woodblock New Year painting is a traditional Chinese folk art that flourished during the 19th and early 20th centuries. These paintings feature a wide variety of colors, particularly after the introduction of synthetic colorants from Europe in the late 19th century. The scientific identification of dyes and pigments used in these paintings can provide valuable insights into the socio-historical context of the time. However, the history of materials used in the printing of New Year paintings is still lacking adequate information. In this study, we employed a combination of spectroscopic and imaging techniques, including Macro X-ray fluorescence imaging (MA-XRF), hyperspectral imaging, and Raman spectroscopy to identify the dyes and pigments used in two Yangliuqing New Year paintings. Our analysis revealed the presence of both traditional pigments and synthetic colorants, such as vermilion, Prussian blue, and methyl/crystal violet. We also discovered several color-matching techniques used to create light pink, light orange, and dark purple hues. These findings suggest that synthetic colorants were gradually replacing traditional pigments in China due to the growth of global trade at that time. Furthermore, our research provides valuable information for the conservation, preservation, and display of New Year paintings.

A neural network algorithm and its prediction model towards the full color phase mixing process of colored fibers

Aiming at the demand of color matching techniques in the spinning process, a neural network prediction model is constructed in this research study, and the gridded full color phase mixing space of colored fibers is used as the sample space. Subsequently, 30 grid points are employed as training samples, while another 30 grid points are adopted as testing samples, in which the parameters of the input, hidden, and output layers are optimized. Additionally, the neural network prediction model is constructed by training samples, and validated by testing samples. Lastly, a neural network prediction model is applied to implement the prediction of color and mixing ratios for any point within the full color phase mixing model. Through the assessment of the testing samples, the predicted results for the colors of the grid point samples showed an average color difference of 1.29 (minimum was 0.22 and maximum was 2.97); the forecasts for the mixing ratios of the colored fibers were that the range of the mean absolute error for the mixing ratios of individual samples was from 0.01% to 0.18%, and the mean absolute error for the mixing ratios of all samples was 0.21%. The experimental results indicated that the proposed neural network model has a relatively advanced prediction accuracy.

Color-matching techniques for creating esthetic hand and finger prostheses.

Color matching is a critically important part of, and by far, also the most challenging aspect of producing esthetic silicone prosthesis. There is a knowledge gap in the literature and a lack of opportunities for training in the expertise, particularly regarding color-matching techniques. This article details a color-matching technique that is able to achieve life-like coloration in esthetic prosthesis. Each prosthesis is molded in an outer and inner layers of silicone tinted to different shades and opacities incorporating an intermediate touch-up layer to reproduce the detailed coloration of the hand (because of the presence of veins, finger joint/dermal pigmentations, a vascularized nail bed, and pinkish palm). This method of color-matching prosthesis combining intrinsic and extrinsic techniques simulates the layered anatomy and optical properties of the human skin to effectively replicate its esthetic and life-like coloration. Technical tips for achieving an accurate color match to the patient's skin, including pigment formulation adjustments for a tanned vs. a fair skin, and for painting the touch-up details are discussed. Methods for modifying the color tones of completed prosthesis and for minimizing metameric color differences when the prosthesis is viewed under different light sources are also presented. The technique is instrumental in achieving good outcomes for life-likeness and esthetic coloration in the prostheses fitted at our center. Studies previously published that investigated patients' evaluation of important esthetic characteristics of their prosthesis after a period of adjustment to fitting have shown a generally high level of patient satisfaction.

A Review of Color Matching in Dentistry

The success of dental treatment is evaluated according to functional and esthetic results. The esthetics of prostheses considered one of the most important parameters of treatment that the patient is interested in. Color matching is an essential procedure to obtain an esthetic prosthesis. Color matching is influenced by several factors, and if not performed properly, it can have unsatisfactory results for both the clinician and the patient. This review discusses color science, factors associated with color perception, and color matching techniques.

Comparative Analysis of Color Matching System for Teeth Recognition Using Color Moment.

BackgroundIn recent years, veritable image processing systems have been developed for several field applications, some of which are recognition and classification. One such application is in the medical field for teeth color matching systems. The color matching technique is a feasible solution for classifying patients’ teeth images to evaluate the suitable treatment of tooth replacement in dentistry. However the lighting conditions of the environment and visual teeth color deficiency will be influenced or affected by the color matching performance.MethodsThis paper proposes the comparative analysis of a color matching system, using K-nearest neighbors (KNN), neural network (NN), and decision tree (DT) algorithms to classify and recognize 16 types of dental images of persons that used several extracted features, from shade guide of teeth, with a digital camera, ranging from 250–300 lux lighting value. The extracted features are produced from RGB, HSV, and Lab color moment characteristic calculation of tooth samples. Those features were compared with input images using euclidean distance value.ResultsKNN algorithm in RGB characteristic achieves 97.5% within only a 0.02 second computation time.ConclusionKNN algorithm in RGB characteristic provides the best performance when compared to the other approaches.

A new patch selection method based on parsing and saliency detection for person re-identification

Person re-identification is an important technique towards automatic recognition of a person across non-overlapping cameras. In this paper, a novel patch selection method based on parsing and saliency detection is proposed. The algorithm is divided into two stages. The first stage, primary selection: Deep Decompositional Network (DNN) is adopted to parse a pedestrian image into semantic regions, then sliding window and color matching techniques are proposed to select pedestrian patches and remove background patches. The second stage, secondary selection: saliency detection is utilized to select reliable patches according to saliency map. Finally, PHOG, HSV and SIFT features are extracted from these patches and fused with the global feature LOMO to compensate for the inherent errors of saliency detection. By applying the proposed method on such datasets as VIPeR, PRID2011, CUHK01, CUHK03, PRID 450S and iLIDS-VID, it is found that the proposed descriptor can produce results superior to many state-of-the-art feature representation methods for person identification.

Performance analysis of color matching technique for teeth classification based on color histogram

Objective: Color matching technique is one of the requirement in clinical dentistry. Using dental shade selection can help the dentist to determine the suitable color for the patients during fabrication of prosthesis. However the lack of dentists’ knowledge in color science due to many kinds of shade guide becomes a problem in the field of dentistry. So color matching technique by using digital images are feasible solution when suitable color features have been properly manipulated.Material and Methods: Separating the color features of digital images into RGB and HSV feature spaces are the first step of this system. Due to many features in this step, it requires some classifier algorithm according to the shade type of teeth. In this paper, we proposed color teeth classification for dental shade selection using DT, NN, and K-nearest neighbors algorithm based on color histogram feature spaces.Results: The result showed that on using the KNN algorithm it achieved 96.67% in learning process and 90% in testing process which had error level (0.183).Conclusion: It proves that our proposed system have high similarity in color matching according to the learning and testing process.

Preliminary evaluation on self-developed dentin porcelain color prediction system

To apply the self-developed dentin porcelain color prediction system in the fabrication of porcelain-fused-to-metal-crown(PFMC), and to evaluate its accuracy in color-matching. Twenty upper central incisors were recruited according to preset criteria, and three PFMC were made for each tooth using three shade-matching techniques. Group A: PFMC were made according to the result of visual color selection; Group B: an spectrophotometer-based color-matching technique was used; Group C: PFMC were fabricated with dentin porcelain powder calculated by the prediction system according to the L(*), a(*), b(*) value measured by a spectrophotometer. Color differences(ΔE) (measured by spectrophotometer) of three groups of crowns were calculated in the cervical, middle, and incisal regions. The results were analyzed using one-way ANOVA. Mean color differences in body regions were: Group A: 3.53±1.80, Group B: 2.86±1.63, Group C: 3.77±1.40(P>0.05), and those in incisal regions were: Group A: 2.70 ± 1.13, Group B: 2.80 ± 0.90, Group C: 3.04 ± 1.03(P>0.05). In cervical region, Group C had greater color difference than Group B(2.78±1.14)(P<0.05). Group A(3.80±2.02) and Group B, Group A and Group C had similar color difference(P>0.05). PFMC fabricated using self-developed dentin porcelain color prediction system had similar color matching compared with conventional and instrument-based methods.

Test illuminant location with respect to the Planckian locus affects chromaticity shifts of real Munsell chips.

The asymmetric sequential color-matching technique was used to determine the shifts in chromaticity of real Munsell chips induced by four test illuminants. The reference illuminant was C. Illuminants green (G) and purple (P) induced shifts orthogonal to the Planckian locus, while illuminants S and A induced shifts along the Planckian locus. Vectors describing the shifts induced by A and S were quantitatively and qualitatively different from those due to G and P. The data suggest that physiological factors, influenced by the proximity of the Planckian locus, affect chromatic constancy under nonsimulated viewing conditions.

Detection of stain formation on teeth by oral antiseptic solution using fiber optic displacement sensor

The application of a simple intensity modulated fiber optic displacement sensor for the detection of stain formation on human teeth is demonstrated. The proposed sensor uses a concentric type bundled plastic optical fiber (POF) as a probe in conjunction with the surfaces of five human teeth as the reflecting targets. Prior to the experiment, the stains were produced extrinsically by soaking the teeth in different concentrations of oral antiseptic solution containing hexetidine. The concentration of the oral antiseptic solution is measured in volume%. For a concentration change from 0% to 80%, the peak voltage decreases exponentially from 1.15mV to 0.41mV with a measured resolution of 0.48% and 1.75% for concentration ranges of 0–40% and 40–80%, respectively. The correlation between the detector output and variation in the color of human tooth surface has successfully been examined. Simple in design and low in cost, this sensor can detect color changes due to hexetidine-induced stain on a tooth surface in a fast and convenient way. Thus, this sensor will be very promising in esthetic dentistry, dental color matching techniques, chemical and biomedical applications.

The Application of Computer Color Matching Techniques to the Matching of Target Colors in a Food Substrate: A First Step in the Development of Foods with Customized Appearance

A predictive color matching model based on the colorimetric technique was developed and used to calculate the concentrations of primary food dyes needed in a model food substrate to match a set of standard tile colors. This research is the first stage in the development of novel three-dimensional (3D) foods in which color images or designs can be rapidly reproduced in 3D form. Absorption coefficients were derived for each dye, from a concentration series in the model substrate, a microwave-baked cake. When used in a linear, additive blending model these coefficients were able to predict cake color from selected dye blends to within 3 ΔE*(ab,10) color difference units, or within the limit of a visually acceptable match. Absorption coefficients were converted to pseudo X₁₀, Y₁₀, and Z₁₀ tri-stimulus values (X₁₀(P), Y₁₀(P), Z₁₀(P)) for colorimetric matching. The Allen algorithm was used to calculate dye concentrations to match the X₁₀(P), Y₁₀(P), and Z₁₀(P) values of each tile color. Several recipes for each color were computed with the tile specular component included or excluded, and tested in the cake. Some tile colors proved out-of-gamut, limited by legal dye concentrations; these were scaled to within legal range. Actual differences suggest reasonable visual matches could be achieved for within-gamut tile colors. The Allen algorithm, with appropriate adjustments of concentration outputs, could provide a sufficiently rapid and accurate calculation tool for 3D color food printing. The predictive color matching approach shows potential for use in a novel embodiment of 3D food printing in which a color image or design could be rendered within a food matrix through the selective blending of primary dyes to reproduce each color element. The on-demand nature of this food application requires rapid color outputs which could be provided by the color matching technique, currently used in nonfood industries, rather than by empirical food industry methods.

Colour matching for soft proofing using a camera

The goal of a colour management system (CMS) is to keep colour across different display devices. For example, a CMS may be developed to preserve colour from monitor to print. Printed colours on paper can look different from colours displayed on a monitor. Soft proofing is to preview a printed colour image on a monitor. The International Colour Consortium (ICC)/ColourSync media profile based on scanner and colorimetric devices are widely used to match between printed and displayed colours. This soft-proofing feature is effective only when accurate ICC profiles of monitor and printer are available with proper lighting condition. In this study, the authors present an on-site monitor-print colour-matching technique for soft proofing that uses a colour-measuring camera when appropriate device and illumination characteristics are not readily accessible. The proposed method consists of two matching steps: one is the estimation of lighting conditions and paper reflectance and the other is the estimation of printer and monitor characteristics. Lighting conditions and paper reflectance are measured by a camera using a white reference patch. Printer and monitor properties can be estimated using a number of colour samples in separate colour components (intensity and chromaticity). A three-dimensional look-up table method is used for intensity mapping, whereas chromatic adaptation is performed by a 2×5 transformation matrix and gamut mapping. Experimental results with several test images demonstrate that the proposed method shows better colour-matching performance, in terms of perceptual quality, than the soft proofing implemented in Photoshop.

Preliminary Study on Application of Computer Color Matching Technique for Wood Dyeing

Wood dyeing requires a non-subjective, repeatable method for determining the color testing and matching. Previously published method used human visual perception to determine the percent of dyestuffs. In this study, computer color matching technique was applied into the dyeing of fast growing wood for the imitation of precious wood species. The process includes measuring the color of wood samples, determining dyeset, preparing and measuring basic color samples, establishing a basic database, calculating and correcting recipes. The recipe of black walnut provided by the system was as follows: acid yellow 2G 0.19%, acid green 0.59%, acid red B 0.29%, with the chromatic difference 0.12%. It could be concluded that dyeing with computer color matching technique allows for a faster, less subjective and easily repeatable procedure that is superior to simple human visual perception.

Clinical performance of a newly developed spectrophotometric system on tooth color reproduction

Matching a natural maxillary central incisor to a metal ceramic crown is one of the most difficult challenges in clinical dentistry due to the limitations of dental shade guides and the subjectivity of perceptual evaluation. The purpose of this study was to assess the clinical effectiveness of a spectrophotometric shade-matching system on tooth color reproduction. Two metal ceramic crowns were fabricated for a maxillary central incisor for 36 patients using 2 shade-matching techniques. The first technique was conventional visual matching using 3 shade guide systems, and the second was an instrument-based color-matching technique using a new spectrophotometric system. Color difference (DeltaE) values between the contralateral natural tooth and each of the 2 crowns were calculated in the cervical, middle, and incisal regions. The DeltaE values were compared using a Student's t test (alpha=.05). Three calibrated examiners evaluated the color match by ranking it from 1 to 10 (10 = perfect match; 1 = no match; < or =8, accepted; > or =7, rejected). McNemar's test was used to calculate the odds ratio of accepting restorations fabricated using a spectrophotometric system to conventional methods. Results revealed that the mean DeltaE values of crowns matched with the spectrophotometer were significantly lower than those using a conventional technique (P<.001). The odds ratio of 12.5 was calculated, indicating that conventionally matched crowns were more likely to be rejected than those matched using the spectrophotometer (P<.001). In this clinical study, crowns fabricated using a dedicated spectrophotometer had a significantly better color match and a lower rate of rejection due to shade mismatch compared to crowns fabricated with a conventional shade-matching method.

Perceived shifts in saturation and hue of chromatic stimuli in the near peripheral retina

Using an asymmetric color matching technique, we measured the perceived changes that occur in the saturation and hue of colored stimuli at different eccentricities within the central 25 degrees of the human retina in nine color-normal subjects. A cone-opponent-based vector model was used to compute the activity of the L-M and S-(L+M) channels. The results show that a large proportion of the shifts in saturation and hue that occur with increasing retinal eccentricity are mirrored by decreased activity of the L-M channel. In comparison, the contribution of the S cone-opponent system undergoes relatively little change within the central 20 degrees . In addition, we also found that changes in saturation and hue are different from each other in terms of their variation across color space and their variation with stimulus size. Our findings suggest that perceived shifts in saturation and hue are mediated largely via the reduction in activation of the L-M cone-opponent channel but that saturation and hue might be subject to different retinal and/or cortical influences that contribute to their differing size dependencies in the peripheral retina.

Reproducibility of tooth color gradation using a computer color-matching technique applied to ceramic restorations

To reproduce tooth color precisely, an objective methodology based on color science is required. However, perception-based techniques are still the primary method for color matching in restorative dentistry. This study evaluated the accuracy of reproduction of color gradation for ceramic restorations using a Computer Color Matching (CCM) technique employing a prototype program and spectrophotometric data measurements. The colors of 10 target-shade tabs of the Vitapan 3D Master shade guide were measured at 4 regions of crowns from the cervical to the incisal area using a spectrophotometer. Tooth-shaped CCM ceramic specimens (30 specimens; 3 specimens for each of 10 target-shade tabs), the same size and shape as target-shade tabs, were fabricated according to the CCM prescriptions calculated using a prototype CCM program. The colors of CCM ceramic specimens and target-shade tabs were compared in 10 incremental areas from gingival to incisal (each measuring 1 mm high x 3 mm wide). The color differences, Delta E, Delta L* , Delta a* , and Delta b* , were calculated. The color difference Delta E values were analyzed by a repeated measures analysis of variance (P <.0001). Three prosthodontists evaluated CCM specimens by perception techniques. The mean color difference (Delta E) values were clinically acceptable (below 3.6) for incremental areas 3 through 10 and unacceptable for areas 1 and 2 (gingival area). Highly significant differences in the mean of Delta E values among target-shade tabs (P <.0001), areas (P <.0001), and target-shade tab-by-area interaction effects (P <.0001) were noted. However, perceptional evaluation indicated "Definitive match" or "Approximate match" for all CCM specimens. The CCM technique tested in this study utilizing 4 measurements on target-shade tabs could reproduce tooth color gradation from incisal to precervical regions with clinically acceptable results.

Change of Color Appearance in Photopic, Mesopic and Scotopic Vision

Mesopic vision describes a range of light levels where vision is mediated by both cones and rods. The appearance of color in mesopic vision differs drastically from that in photopic vision, where only cones mediate visual information. We used a haploscopic color matching technique to investigate the color appearance under various illuminance levels, ranging from photopic to scotopic via mesopic levels. The observers did color matching between a test color chip under various illuminance levels and a matching color stimulus presented on the Cathode-Ray Tube (CRT) display under the photopic illuminance condition. The results showed that not only chroma and lightness but hue of most color chips changed with illuminance. The manner of the hue changed depended on the color of the test chip, while matching points approached a neutral gray with decrease in illuminance level for all test chips. Chroma reduced continuously with decrease of the illuminance level until 0.1 lx for reddish and yellowish color chips or until 1 lx for greenish and bluish ones. Beyond those illuminance levels, chroma was approximately constant. Lightness decreased with decreasing illuminance level for all test chips except bluish color chips, for which lightness did not decrease much in general and even increased in some cases as predicted by the Purkinje shift. The experimental results obtained in the present study provide critical features that should be considered in predicting the appearance of color at low light levels.

An image-based system for electronic retailing

The purpose of this paper is to describe a methodology for enhancing search and retrieval of product information using content-based image retrieval in an electronic retailing application. Content-based image retrieval techniques have been applied to various applications such as medical information systems, environmental modeling, and satellite image analysis. Such techniques, however, can also be useful in electronic commerce applications such as electronic retailing, by enhancing product search and computer-assisted sales. In this paper, we describe an application of CBIR in electronic retailing using color and texture matching techniques. We describe a prototype system in the context of the apparel industry.

Discrimination of illumination and reflectance changes on color constancy

Human perception of the color of physical surfaces is practically not affected by changes in illumination. This phenomenon is called color constancy. Based on results of previous psychophysical experiments, it has been established that there are two types of color perception: apparent color and surface color. It has also been suggested that unless there is a complete adaptation to the illuminant, color constancy can be achieved only with respect to the surface color. Computational models of color constancy boil down to problems of estimation of reflectance of the observed object based on the magnitude of the sensory response, and duality of color perception has not been adequately addressed in previous studies. This study was undertaken for the purpose of making clear the characteristics of the two types of color perception (apparent color and surface color). The experimental technique used in this study was based on the detection of changes of illuminance and reflectance for the purposes of determination of the effect of the surround stimulus on color perception, rather than on conventional color matching technique. The results of the study indicate that the surround stimulus exhibits an inhibitive influence on the color perception of the center stimulus, and the effect of the size and spatial structure of the surround stimulus is different with respect to the apparent color and the surface color. It was also demonstrated that results of the experiments can be explained by a hypothesis of a hierarchical structure of the vision system combining two different types of color perception. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 83(11): 43–55, 2000