CIE XYZ Research Articles

Enhanced Field-Based Detection of Potato Blight in Complex Backgrounds Using Deep Learning.

Rapid and automated identification of blight disease in potato will help farmers to apply timely remedies to protect their produce. Manual detection of blight disease can be cumbersome and may require trained experts. To overcome these issues, we present an automated system using the Mask Region-based convolutional neural network (Mask R-CNN) architecture, with residual network as the backbone network for detecting blight disease patches on potato leaves in field conditions. The approach uses transfer learning, which can generate good results even with small datasets. The model was trained on a dataset of 1423 images of potato leaves obtained from fields in different geographical locations and at different times of the day. The images were manually annotated to create over 6200 labeled patches covering diseased and healthy portions of the leaf. The Mask R-CNN model was able to correctly differentiate between the diseased patch on the potato leaf and the similar-looking background soil patches, which can confound the outcome of binary classification. To improve the detection performance, the original RGB dataset was then converted to HSL, HSV, LAB, XYZ, and YCrCb color spaces. A separate model was created for each color space and tested on 417 field-based test images. This yielded 81.4% mean average precision on the LAB model and 56.9% mean average recall on the HSL model, slightly outperforming the original RGB color space model. Manual analysis of the detection performance indicates an overall precision of 98% on leaf images in a field environment containing complex backgrounds.

The Application of Machine Learning for Cultivar Discrimination of Sweet Cherry Endocarp

The aim of this study was to evaluate the usefulness of the texture and geometric parameters of endocarp (pit) for distinguishing different cultivars of sweet cherries using image analysis. The textures from images converted to color channels and the geometric parameters of the endocarp (pits) of sweet cherry ‘Kordia’, ‘Lapins’, and ‘Büttner’s Red’ were calculated. For the set combining the selected textures from all color channels, the accuracy reached 100% when comparing ‘Kordia’ vs. ‘Lapins’ and ‘Kordia’ vs. ‘Büttner’s Red’ for all classifiers. The pits of ‘Kordia’ and ‘Lapins’, as well as ‘Kordia’ and ‘Büttner’s Red’ were also 100% correctly discriminated for discriminative models built separately for RGB, Lab and XYZ color spaces, G, L and Y color channels and for models combining selected textural and geometric features. For discrimination ‘Lapins’ and ‘Büttner’s Red’ pits, slightly lower accuracies were determined—up to 93% for models built based on textures selected from all color channels, 91% for the RGB color space, 92% for the Lab and XYZ color spaces, 84% for the G and L color channels, 83% for the Y channel, 94% for geometric features, and 96% for combined textural and geometric features.

A Perceptual Color-Matching Method for Examining Color Blending in Augmented Reality Head-Up Display Graphics.

Augmented reality (AR) offers new ways to visualize information on-the-go. As noted in related work, AR graphics presented via optical see-through AR displays are particularly prone to color blending, whereby intended graphic colors may be perceptually altered by real-world backgrounds, ultimately degrading usability. This work adds to this body of knowledge by presenting a methodology for assessing AR interface color robustness, as quantitatively measured via shifts in the CIE color space, and qualitatively assessed in terms of users' perceived color name. We conducted a human factors study where twelve participants examined eight AR colors atop three real-world backgrounds as viewed through an in-vehicle AR head-up display (HUD); a type of optical see-through display used to project driving-related information atop the forward-looking road scene. Participants completed visual search tasks, matched the perceived AR HUD color against the WCS color palette, and verbally named the perceived color. We present analysis that suggests blue, green, and yellow AR colors are relatively robust, while red and brown are not, and discuss the impact of chromaticity shift and dispersion on outdoor AR interface design. While this work presents a case study in transportation, the methodology is applicable to a wide range of AR displays in many application domains and settings.

Digital image colorimetry on smartphone for chemical analysis: A review

Digital image colorimetry (DIC) on smartphone is regarded as a powerful, fast and low-cost analysis method to measure target analyte with color changes of digital image obtained by the built-in camera. We summarized the basic procedure of DIC, the color spaces (RGB, CMYK, HSB/HSL, CIE XYZ, L*a*b*, and YUV), the principal architectures (tools for capturing image, lighting conditions, and color quantification APPs and DIC APPs), and current status of DIC on smartphone in analysis of metals/heavy metals, herbicides, pesticides, antibiotics, biological and medical indicators, natural compounds, and bacteria/viruses. The advantages and disadvantages of DIC are also revealed. Nowadays, DIC on smartphone must be further refined with controlled geometry and standard lighting sources to become robust and reliable analytical procedures. And it will be improved in the near future with the continuous development of smartphones owing to the rapid development of smartphone’s camera technology and the continuous optimization of related software.

A Mathematical Investigation into the Design of Prefilters That Make Cameras More Colorimetric.

By placing a color filter in front of a camera we make new spectral sensitivities. The Luther-condition optimization solves for a color filter so that the camera’s filtered sensitivities are as close to being linearly related to the XYZ color matching functions (CMFs) as possible, that is, a filter is found that makes the camera more colorimetric. Arguably, the more general Vora-Value approach solves for the filter that best matches all possible target spectral sensitivity sets (e.g., any linear combination of the XYZ CMFs). A concern that we investigate here is that the filters found by the Luther and Vora-Value optimizations are different from one another. In this paper, we unify the Luther and Vora-Value approaches to prefilter design. We prove that if the target of the Luther-condition optimization is an orthonormal basis—a special linear combination of the XYZ CMFs which are orthogonal and are in unit length—the discovered Luther-filter is also the filter that maximizes the Vora-Value. A key advantage of using the Luther-condition formulation to maximize the Vora-Value is that it is both simpler to implement and converges to its optimal answer more quickly. Experiments validate our method.

Designing a Color Filter via Optimization of Vora-Value for Making a Camera more Colorimetric

Previous work has proposed to solve for a filter which, when placed in front of a camera, improves the colorimetric property by best satisfying the Luther condition. That is, the filtered spectral sensitivities of a camera - after a linear transform - are as close to the color matching functions of the human visual system as possible. By construction, the prior art solves for a filter for a given set of human visual sensitivities, e.g.the XYZ color matching functions or the cone response functions. However, depending on the target spectral sensitivity set, a different optimal filter is found. In this paper, we set out a method to solve for a filter that works equally well for all possible target sensitivity sets of the human visual system. We observe that the cone fundamentals, the CIE XYZ color matching functions or any linear combination thereof, span the same vector space. Thus, we solve for a filter that makes the vector space spanned by the filtered camera sensitivities as similar as possible to the space spanned by human vision sensors. We argue that the Vora-Value is a suitable way to measure subspace similarity and we develop an optimization method for finding a filter that maximizes the Vora-Value measure. Experiments demonstrate that our new optimization leads to the filtered camera sensitivities which have a significantly higher Vora-Value and improved colorimetric performance compared with antecedent methods.

A Correspondence-Free Color Chart Design for Color Calibration

Colorimetric calibration computes the necessary color space transformation to map a camera's device-specific color space to a device-independent perceptual color space. Color calibration is most commonly performed by imaging a color rendition chart with a fixed number of color patches with known colorimetric values (e. g., CIE XYZ values). The color space transformation is estimated based on the correspondences between the camera's image and the chart's colors. We present a new approach to colorimetric calibration that does not require explicit color correspondences. Our approach computes a color space transformation by aligning the color distributions of the captured image to the known distribution of a calibration chart containing thousands of colors. We show that a histogram-based colorimetric calibration approach provides results that are onpar with the traditional patch-based method without the need to establish correspondences.

Designing a physically-feasible colour filter to make a camera more colorimetric

Previously, a method has been developed to find the best colour filter for a given camera which results in the new effective camera sensitivities that best meet the Luther condition. That is, the new sensitivities are approximately linearly related to the XYZ colour matching functions. However, with no constraint, the filter derived from this Luther-condition based optimisation can be rather non-smooth and transmit very little light which are impractical for fabrication. In this paper, we extend the Luther-condition filter optimisation method to allow us to incorporate both the smoothness and transmittance bounds of the recovered filter which are key practical concerns. Experiments demonstrate that we can find physically realisable filters which are smooth and reasonably transmissive with which the effective 'camera+filter' becomes significantly more colorimetric.

Characterization of the Caput Mortuum purple hematite pigment and synthesis of a modern analogue

This investigation addressed the characterization and the production methods of the purple pigmentCaput Mortuum used since pre-historic times until the eighteenth century. Literature hypotheses for its production after heating of ochres/Fe-hydroxides, with addition of white minerals of different composition has been experimentally reproduced, and disproved. An original synthesis after massive hematite that underwent fine grinding, followed by high temperature (900–1100 °C) annealing under oxidative conditions was carried out.Several natural and synthetic starting Fe-oxides and hydroxides were tested with these procedures, followed by compositional (X-Ray Powder Diffraction), spectroscopic (Reflectance spectroscopy, colorimetric measurements and Lab CIE color space), microscopic (Scanning Electron Microscopy coupled with Energy Dispersive Spectrometry), and magnetic characterization.The color changes undergone by hematite from red to purple could be mainly traced back to the grain dimensions resulting from the annealing process. The experiments on synthetic starting materials allowed excluding that the final color is affected by impurities. Moreover, it was determined that a purple ochre could not be obtained by thermal treatment of natural earths and that the purple pigment could only be manufactured by starting from hematite and not from red ochre.Finally, magnetic measurements further discriminated among different Caput Mortuum types.

Robust Chromatic Adaptation Based Color Correction Technology for Underwater Images

Recovering correct or at least realistic colors of underwater scenes is a challenging issue for image processing due to the unknown imaging conditions including the optical water type, scene location, illumination, and camera settings. With the assumption that the illumination of the scene is uniform, a chromatic adaptation-based color correction technology is proposed in this paper to remove the color cast using a single underwater image without any other information. First, the underwater RGB image is first linearized to make its pixel values proportional to the light intensities arrived at the pixels. Second, the illumination is estimated in a uniform chromatic space based on the white-patch hypothesis. Third, the chromatic adaptation transform is implemented in the device-independent XYZ color space. Qualitative and quantitative evaluations both show that the proposed method outperforms the other test methods in terms of color restoration, especially for the images with severe color cast. The proposed method is simple yet effective and robust, which is helpful in obtaining the in-air images of underwater scenes.

An efficient nonlinear polynomial color characterization method based on interrelations of color spaces

AbstractA well‐known color characterization method is to take an image of a color chart and then to find the mapping matrix from the digital RGBs to the corresponding known CIEXYZs. However, the prediction errors are generally large in CIELAB color space because of the nonlinear transformation from CIEXYZs to CIELABs. In this article, we propose an efficient and simple nonlinear method for the color characterization of input devices. The approach for deriving a colorimetric mapping between digital RGB signals and CIELAB tristimulus values uses the polynomial modeling by considering the interrelations among the standard CIE color spaces. Furthermore, to improve the accuracy of solution, we take the polynomial root terms extension. Our algorithm is simple to implement because only a least‐squares mapping should be solved. Various computational results are given to demonstrate the efficiency and capability of the proposed method.

Optical effect of spraying l-menthol on gastric intestinal metaplasia visualized by linked color imaging.

Linked color imaging (LCI) enables noninvasive detection of gastric intestinal metaplasia (GIM) as a lavender color sign (LCS), and there has been a recent report that l-menthol enhanced GIM with LCI. We measured color values of GIM and surrounding mucosa with white light imaging (WLI), LCI and LCI after spraying l-menthol (Mint-LCI) and investigated the effect of l-menthol on gastric mucosa. Endoscopic images of the antrum with WLI, LCI and Mint-LCI from 18 patients were prepared. Each of six regions of interest (three points of GIM and three points of surrounding mucosa) was selected for each modality, and CIE1976 (L*a*b*) color space was used to measure the color values. The primary endpoint was color differences (ΔE) between GIM and surrounding mucosa in each modality. For surrounding mucosa, the mean a* value with Mint-LCI was significantly higher than the mean values with WLI and LCI (P < 0.01). The mean b* value of GIM with LCI was significantly lower than that of surrounding mucosa, and spraying l-menthol decreased the b* values of GIM with a change to a deeper lavender color (LCI: 10.0 ± 5.8, Mint-LCI: 3.7 ± 6.1, P < 0.01). However, there was no significant difference in mean ΔE values between LCI and Mint LCI (LCI: 21.1 ± 6.6, Mint-LCI: 22.7 ± 5.4, NS). After spraying l-menthol, the microstructure of GIM changed to translucent and microvessels were obscured. As shown by LCI, spraying l-menthol optically enhances the color of GIM in the antrum.

Design and investigation of a digital photocolorimeter

In this study, a digital photocolorimeter was developed based on a detector matched with an intrinsic operational color space and a set of optical filters. The color space M2′N2′P2′ with properties similar to the curves of the CIE XYZ 1931 system was used. Software was developed for processing of black-and-white images to operate the digital colorimeter. The image processing algorithm in the CIE LAB system is explained and the experimental procedure for determining the color coordinates of samples in the M2′N2′P2′ color space using X1X2Y1Z1 detectors is described herein. The color difference between green, yellow–green, and yellow optical filters was determined for an objective assessment of the quality of the developed system. Subsequently, an analysis of the experimental values was performed, and our system exhibited satisfactory results. The possible applications of the developed photocolorimeter are also proposed.

Structural, Morphological and Photoluminescence Studies of Pure ZrO2 and ZrO2: Eu+3 Nanophosphors Synthesised by Microwave-Assisted Hydrothermal Technique

The luminescence properties of pure and ZrO2: Eu+3 nanophosphors with different concentration of the Eu+3 is synthesised and studied. A novel and environment benign microwave-induced hydrothermal process is used to synthesise the nanoparticles. As-formed pure ZrO2 nanoparticles were X-ray amorphous, and upon calcination at higher temperatures, they crystallise to a combination of both cubic and tetragonal phases. However, the ZrO2: Eu+3 nanophosphors prepared through the same technique under similar conditions yield exclusively cubic ZrO2, and it entirely depends on the concentration of Eu+3 as revealed by XRD studies. The nanoparticles are found to be spherical, non-porous and agglomerated as observed by SEM. The surface area of the nanoparticles of pure ZrO2 is found to be 30 m2/g for as-formed samples and 130 m2/g for calcined samples by BET studies. The increase in the surface area for calcined sample is due to the escaping of the adsorbed hydroxyl groups from the surface of the nanoparticles. The photoluminescence properties of the pure and Eu+3-doped ZrO2 nanoparticles were measured under 251 nm excitation wavelength. Under this excitation, pure ZrO2 gives the emissions at 394 nm, whereas Eu+3-doped nanoparticles gives the emissions at 613 nm, which corresponds to inter-f-f transition from 5D0 ➔7F2 (613 nm) and is arising due to electronic dipole in the Eu+3 activator ion. CIE colour space (x, y) coordinates corresponding to 613 nm in the CIE chromaticity diagram is 0.680, 0.319.

The effect of sugar type and baking condition on formation of acrylamide in industrial rotary moulded biscuit

The purpose of current study is to monitor the Acrylamide (AA) contents in biscuits produced on the industrial scale. Effect of sugar types, inverted sugar syrup and sucrose, and baking conditions including time and temperature on the AA formation were studied in rotary moulded biscuit at the industrial scale. The AA content and the correlation between AA concentration and CIE color space parameters of L*a*b* and C index was studied. The AA formation was effectively decreased by replacement of the inverted sugar syrup of 2% w/w with sucrose of 1% w/w. The least AA content was found in samples made with 5% inverted sugar and 15% sucrose and the highest concentration of AA was observed in samples made with 9% inverted sugar and 13% sucrose. The effect of sugar on acrylamide formation was pronounced for inverted sugar and sucrose, expectedly. To assess the effect of baking condition, increasing the mean temperature of three zones of tunnel oven from 307 to 320 °C led to rising AA concentration, while the amount of AA reduced with increasing the mean oven temperature from above 320 °C. The results of the color analysis of biscuit samples revealed that a significant correlation was observed between AA concentration and brightness parameter L*, while parameters a*, b* and C did not show significant differences. The overall results suggest that the industrial rotary moulded biscuit without any difference in overall acceptability, but having the lowest acrylamide content can be manufactured by decreasing the baking mean temperature for a long time and also replacing inverted sugar syrup with sucrose.

Chroma-hue controllable color and thermocolor-added deoxyribonucleic acid films

Deoxyribonucleic acid (DNA) is a useful scaffolding material for the alignment of nanomaterials with specific functionalities. Here, we fabricated multi-layered (e.g., single, triple, and quintuple) color-added DNA films with a different color in each layer on substrates as well as a self-supported film with a mixture of different colors. A color-added DNA thin film on a substrate was prepared by either drop-casting or spin-coating, and a self-supporting DNA film was constructed by an oven-drying procedure. The optical characteristics of DNA films with various color dye concentrations were studied through transmittance and absorption. In addition, color profiles (i.e., chroma and hue angle) of the self-supporting DNA films were investigated by considering reflectance to obtain International Commission on Illumination LAB (CIELAB) values (where L, A, and B represent the brightness, x-axis (green-red), and y-axis (yellow-blue) in the CIE color space, respectively). Color profiles were obtained by L, A, and B. The chroma of the self-supporting DNA film with more colors were relatively small, indicating a dark achromatic characteristic of the samples. The hue angle of each film corresponded to the characteristic colors. Finally, the reversibility of the color change of DNA films embedded with thermochromatic dyes was demonstrated by varying the temperature to verify use in practical applications.

Pedestrian lane and obstacle detection for blind people

Pedestrian lane and obstacle detection have been a big problem for a blind person. The person has to use special tool or assistant to do daily activities. This work has utilized camera function, connected with data processing (mini PC) to process information captured by a camera. At first, RGB image, which was captured camera, was converted into XYZ colour system. This colour system was very useful to highlight pedestrian lane to reduce other objects. Then, colour filter was implemented to remove unnecessary objects, followed by close morphology to expose pedestrian lane. The result is white region which represent pedestrian lane. Major axis was then calculated using moments and its angle (calculated counter clockwise with reference to x-axis) was sent to the user to notify him/her which direction he/she can go. In the process of obstacle detection, some samples of RGB images has been used to train a neural network. The model was then used as obstacle detector. RGB images captured by camera were then used as test data. The result > 0.7 was considered as obstacle. The experiment shows that under illumination of <15000 lux, the method can achieve 89.7 percentage accuracy on pedestrian lane detection and 100 percentage accuracy on obstacle detection.

Simple and affordable imaging of multiple physiological parameters with RGB camera-based diffuse reflectance spectroscopy.

We propose a simple and affordable imaging technique to evaluate transcutaneously multiple physiological parameters by using a digital red-green-blue camera. In this method, the RGB-values were converted into tristimulus values in the CIE (Commission Internationale de l'Eclairage) XYZ color space, which is compatible with the common color spaces. Monte Carlo simulation for light transport in biological tissue was then performed to specify the relationship among the XYZ-values and the concentrations of oxygenated hemoglobin, deoxygenated hemoglobin, bilirubin, and melanin. The concentration of total hemoglobin and tissue oxygen saturation were also calculated from the estimated concentrations of oxygenated and deoxygenated hemoglobin. In vivo experiments with bile duct ligation in rats demonstrated that the estimated bilirubin concentration increased after ligation of the bile duct and reached around 22 mg/dl at 116 h after the onset of ligation, which corresponds to the ground truth value of bilirubin measured by a commercially available transcutaneous bilirubinometer. Experiments with rats while varying the fraction of inspired oxygen demonstrated that oxygenated hemoglobin and deoxygenated hemoglobin decreased and increased, respectively, as the fraction of inspired oxygen decreased. Consequently, tissue oxygen saturation dramatically decreased. We further extended the method to a non-contact imaging photo-plethysmograph and estimation of the percutaneous oxygen saturation. An empirical formula to estimate percutaneous oxygen saturation was derived from the pulse wave amplitudes of oxygenated and deoxygenated hemoglobin. The estimated percutaneous oxygen saturation dropped remarkably when a faction of inspired oxygen was below 19%, indicating the onset of hypoxemia due to hypoxia, whereas the tissue oxygen saturation decreased gradually according to the reduction of the faction of inspired oxygen. The results in this study indicate the potential of this method for imaging of multiple physiological parameters in skin tissue and evaluating an optical biomedical imaging technique that enables cost-effective, easy-to-use, portable, remotely administered, and/or point-of-care solutions.

Light amplification in tunable multicolor liquid crystalline system

Multicolor emission exhibited by complex organic systems is interesting and desired phenomenon for many optical applications. Laser devices capable to emit the light in the spectral range of three fundamental colors (red, green and blue) can revolutionize the modern display and lighting technologies. In this paper we demonstrate a multicolor stimulated emission (STE) phenomenon obtained in dye doped, liquid crystalline (LC) material. The polychromatic STE was obtained for LC cell, filled with nematic mesophase doped with three luminescent dyes. The CIE XYZ chromaticity diagram (1931) demonstrates effective color modulation with respect to relative concentration of utilized dyes and applied voltage. The precise color adjustment can be provided by applying the external electric DC fields, with voltages ranging from 0 to 20 V.

Comparison of n-LSB embedding approach in different color spaces

Today, secure communication is one of the biggest goals that people want to achieve. There are many different methods to ensure security in data communication. Steganography is one of the methods that can be used in secure data communication. In this study, n-LSB embedding method based on reducing the amount of distortion generated by the classical Least Significant Bit substitution method that we introduced in another study has been applied in both RGB color space and HSI, XYZ and YCbCr color spaces. In the embedding process, 3 message bits were embedded in each color channel. 7.94 kb data is embedded on 3 different cover images. The obtained results were compared with the PSNR criterion, which is the criterion of image quality evaluation, and it is seen that proposed n-LSB approach gives better results in HSI color space for 3 cover images. The highest PSNR value obtained was 83.907 dB.