Color Reproduction Research Articles

A Color Calibration Method Based on Color Component Projection for Suppression of False Color Caused by Iterative Distribution Transfer

Different imaging conditions often result in different color reproductions. Hence, color reproductions must be calibrated when images are captured under different imaging conditions. Herein, a new color calibration method based on iterative distributed transfer (IDT) is proposed. IDT is used to preliminarily calibrate color reproductions, and the results are known as preliminary results. Because IDT may result in unnatural colors, namely false colors, the projected color components of the input image are used to suppress the false colors, and the results are the final results. To obtain the final results, a series of projection coefficients must be calculated. By minimizing the objective function, in which the preliminary results are used as the target for the final results, the projection coefficients are calculated. Simultaneously, the weight associated with the false color is incorporated into the objective function such that the final results do not depend significantly on the preliminary results when the IDT yields false colors. Meanwhile, to quantitatively evaluate the false color, a false color index is proposed herein. The proposed method can suppress false colors and offers high color-adjustment capabilities. The effectiveness of the method is verified based on evaluation indexes and the observation of experimental results.

The Color Improvement of Underwater Images Based on Light Source and Detector.

As one of the most direct approaches to perceive the world, optical images can provide plenty of useful information for underwater applications. However, underwater images often present color deviation due to the light attenuation in the water, which reduces the efficiency and accuracy in underwater applications. To improve the color reproduction of underwater images, we proposed a method with adjusting the spectral component of the light source and the spectral response of the detector. Then, we built the experimental setup to study the color deviation of underwater images with different lamps and different cameras. The experimental results showed that, a) in terms of light source, the color deviation of an underwater image with warm light LED (Light Emitting Diode) (with the value of being 26.58) was the smallest compared with other lamps, b) in terms of detectors, the color deviation of images with the 3×CMOS RGB camera (a novel underwater camera with three CMOS sensors developed for suppressing the color deviation in our team) (with the value of being 25.25) was the smallest compared with other cameras. The experimental result (i.e., the result of color improvement between different lamps or between different cameras) verified our assumption that the underwater image color could be improved by adjusting the spectral component of the light source and the spectral response of the detector. Differing from the color improvement method with image processing, this color-improvement method was based on hardware, which had advantages, including more image information being retained and less-time being consumed.

An Exploration into Color Reproduction for Inkjet FDM Color 3D Printing

Advancing in inkjet fused deposition modeling (FDM) color 3D printing enables to create dedicated aesthetical appeal. However, the complete fabrication of a target color remains limited due to the unusual mismatch in 3D color management systems. In particular, the 3D aspect that makes the 3D color systems different from standard 2D printing, such as ink and substrate characteristics, viewing conditions, and base materials. Therefore, to the best of our knowledge, there is no suitable established method that supports color reproduction for inkjet FDM color 3D printing. In this paper, we analyze the color profile of an inkjet FDM color 3D printer to obtain a color model that could bridge the gap between a digital design (as an input) and the actual 3D printed results (as an output). We then created the color model by reproducing each color mapped to every possible color pair to determine the closest color between the target and printing colors on the basis of the color difference value, which can be rendered in lieu of the original printing colors. We verify our proposed color model by printing the mapped color and conduct a color measurement to compare it with the target colors. From the experimental results, we showed that our mapped colors can represent those desired by the user with an 80% success rate, which can be matched through controlled conditions.

DePhaseNet: A deep convolutional network using phase differentiated layers and frequency based custom loss for RGBW image sensor demosaicing

Panchromatic Color Filter Arrays with white signal were introduced a while ago, such as RGBW Kodak (CFA2.0) array, assuming to have better resolution in lowlight due to panchromatic signal. However, there is no successful RGBW image sensor in the industry targeting mobile cameras until now. In this work, we introduce a novel Samsung RGBW image sensor and we study its performance in a popular remosaic scenario. We propose a DePhaseNet - a deep fully convolutional network to solve RGBW remosaicing or demosaicing problem. We propose to have 3 layers of phase differentiated inputs and custom frequency based loss function for each layer. Proposed method successfully suppress False Colors inherent to RGBW sensor due to heavily under-sampled colors. By using this method, we were able not only to increase details preservation, but also increased color reproduction by 2% over conventional method. We found that RGBW sensor is beneficial not only in low light scenarios, but also in widely spread remosaic scenarios. Experiments show improvement in image quality, yielding CPSNR of 42dB for Kodak dataset, reaching the bar of Bayer CFA demosaicing result. Proposed method advances state-of-the-art in RGBW demosaic, by 6dB in CPSNR.

Colour Recognition Algorithm Based on Colour Mapping Knowledge for Wooden Building Image

In the cross-media image reproduction technology, the accurate transfer and reproduction of colour between different media are an important issue in the reproduction process, and the colour mapping technology is the key technology to effectively maintain the image details and improve the level of colour reproduction. Wooden structure in the image colour and colour piece is different, the image of each colour of visual perception is not independent, and every colour in the image pixels is affected by the surrounding pixels, but in the process of image map, without thinking of the pixel space, adjacent pixels of mutual influence in particular, do not let a person particularly be satisfied with the resulting map figure. In the process of image processing by traditional colour mapping algorithm, the colour distortion caused by colour component is ignored and the block diagram of colour mapping system is constructed. With the continuous development of mapping recognition algorithms, the maximum and minimum brightness values in the image are mapped to the maximum and minimum brightness values of the display device by linear mapping algorithm according to the flow of the established recognition algorithm. By establishing the colour adjustment method of the colour mapping image, the processing effect of the mapping algorithm is analysed. The results show that the brightness deviation of the image is reduced and the colour resolution is improved by the colour brightness compensation.

ColorPolarNet: Residual Dense Network-Based Chromatic Intensity-Polarization Imaging in Low-Light Environment

Polarization imaging provides more dimensional information than traditional intensity imaging and has been widely used in both military and civil areas, such as battlefield reconnaissance, environmental monitoring, autonomous driving and so on. With the rapid development of color polarization imaging sensors, polarization detection that allows simultaneous acquisition of multiple images (intensity maps modulated by different polarizers) and real-time extraction of polarization information is becoming increasingly mature. However, the imaging quality of color polarization camera is always unsatisfactory in low light environment with low-photon count. In this paper, we present a residual dense blocks-based multi-task convolutional network, called ColorPolarNet, to extract and enhance the intensity and polarization information from four RGB polarized light intensity images captured in low light environment with different polarization orientations (0°,45°,90° and 135°). This proposed network consists of two parts: (1) an intensity network for initial denoising and color deviation correction of the four polarized light intensity maps; (2) a polarization difference network used to enhance the details of the total intensity ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) map, the degree of linear polarization (DoLP) map and the angle of polarization (AoP) map. Also, to train the model, we collect a low light chromatic polarization (LLCP) dataset that contains 300 paired datasets of low-normal light images captured indoors and outdoors. Both qualitative and quantitative experimental results show that the proposed ColorPolarNet outperforms other conventional low light image enhancement methods in terms of signal fidelity, contrast enhancement and color reproduction. Our codes and the LLCP dataset are available at https://github.com/MinjieWan/ColorPolarNet.

Image Enhancement Algorithm Based on GAN Neural Network

Deep underwater color images have problems such as low brightness, poor contrast, and loss of local details. In order to effectively enhance low-quality underwater images, this paper proposes an enhancement method based on GAN (Generative Adversarial Network). This paper studies low-light image enhancement algorithms, aiming to improve the quality of low-light images by studying some technical means and methods, and restore the original scene information of low-quality images, so as to obtain natural and clear images with complete details and structural information. In order to verify the effectiveness of this method, image databases such as DIARETDB0 and SID are used as the research object, combined with multi-scale Retinex color reproduction contrast-constrained adaptive histogram equalization to compare the performance of the enhanced algorithm. The results show that the processed image is better than other image enhancement methods in terms of color protection, contrast enhancement, and image detail enhancement. The proposed method significantly improves the indicators proposed in the article.

СРАВНИТЕЛЬНАЯ ХАРАКТЕРИСТИКА ИНСТРУМЕНТАЛЬНЫХ И АППАРАТНЫХ МЕТОДОВ ОПРЕДЕЛЕНИЯ ЦВЕТА ЗУБОВ (ОБЗОР ЛИТЕРАТУРЫ) / COMPARATIVE CHARACTERISTICS OF CONVENTIONAL VISUAL METHODS AND INSTRUMENTAL DIGITAL METHODS FOR TOOTH COLOR DETERMINATION

Shade matching in is a challenging step and major objective in esthetic and restorative dentistry. On many occasions, production of the accurate, target color will not be achieved due to errors in registration of the target color, or errors in composing the appropriate color of the restoration in the dental laboratory. Thus, the accurate and correct shade matching of tooth and restoration is is one of the most important quality criteria for the patient and the key to successful results for the dentist. Conclusion: Spectrophotometers, colorimeters, intraoral scanners and imaging systems are useful and relevant tools for tooth color measurement and analysis, and for quality control of color reproduction. Combination of visual and instrumental methods of tooth color determination will complement each other and can lead towards predictable esthetic results .

Кольоровідтворення відбитків цифрового та офсетного друку

Кольоровідтворення відбитків цифрового та офсетного друку

Adsorption of a Spiropyran on a Layered Clay Mineral

Adsorption of a photochromic dye, spiropyran, on a layered clay mineral, a synthetic hectorite, was investigated. Spiropyrans are well-known photochromic molecules due to its fast and reproducible color change resulting from the photoisomerization between hydrophobic closed-ring spiropyran and hydrophilic open-ring merocyanine. The photochemical reaction of the adsorbed spiropyran in the modified hectorite was also examined.

패키지 인쇄에 있어서 Kubelka-Munk Model 유래의 산란 및 흡수 계수를 이용한 색상 재현성 예측

With the development of package printing technology, the package has expanded from the basic function of protecting products to the marketing function through package design. Color, the visual element that composes the package design, is delivered to the consumer most quickly and effectively. As color marketing of these package designs expands, accurate color reproduction that the product wants to express is becoming more important. The color of an object is transmitted by absorption and scattering of light. Spectral reflectance refers to the intensity of light reflected by an object at different wavelengths by the spectral effect. As a result, the color of the object is expressed in various colors. Packaged printing inks have their own absorption and scattering coefficients, and the Kubelka-Munk model for color reproduction and prediction defines the relationship between these correlation coefficients through reflectance. In the Kubelka-Munk model for color reproduction and prediction, the relationship between the absorption and scattering coefficients (K/S) of printed material is predicted as the sum of the K/S values according to the mixing ratio of all color ink used. In this study, the reflectance of the measured print is reversely calculated at the mixing ratio of print ink using the Kubelka-Munk model. Through this, the relationship value of the ink-specific absorption/scattering coefficient constituting the final printed material is predicted. Delta E is derived through the predicted reflectance, and the similarity between the measured value and the predicted value is confirmed.

Powerful Direct C-H Amidation Polymerization Affords Single-Fluorophore-Based White-Light-Emitting Polysulfonamides by Fine-Tuning Hydrogen Bonds.

The development of white-light-emitting polymers has been actively pursued because of the importance of such polymers in various applications, such as lighting sources and displays. To generate white-light, numerous research efforts have focused on synthesizing multifluorophore-based random copolymers to effectively cover the entire visible region. However, due to their intrinsic synthetic and structural features, this strategy has limitations in securing color reproducibility and stability. Herein, we report the development of single-fluorophore-based white-light-emitting homopolymers with excellent color reproducibility. A powerful direct C-H amidation polymerization (DCAP) strategy enabled the synthesis of defect-free polysulfonamides that emit white-light via excited-state intramolecular proton-transfer (ESIPT). To gain structural insights for designing such polymers, we conducted detailed model studies by varying the electronic nature of substituents that allow facile tuning of the emission colors. Further analysis revealed precise control of the thermodynamics of the ESIPT process by fine-tuning the strength of the intramolecular hydrogen bond. By applying this design principle to polymerization, we successfully produced a series of well-defined polysulfonamides with single-fluorophore emitting white-light. The resulting polymers emitted consistent fluorescence, regardless of their molecular weights or phases (i.e., solution, powder, or thin film), guaranteeing excellent color reproducibility. With these advantages in hand, we also demonstrated practical use of our DCAP system by fabricating a white-light-emitting coated LED.

Influence of the surface characteristics of corrugated cardboard on the quality of inkjet printing

This paper investigates the quality of inkjet printing on corrugated cardboard with various characteristics such as the presence of surface coating, the type of cardboard structure, the corrugated layer profile, and the corrugated cardboard height. The color characteristics of the corrugated board surface of studied samples were analyzed in the CIE Lab system; the value of the discrepancy in the shade of white was established when compared with the reference values of the ISO 12647 standard. During the study, the main criteria for assessing the quality of color reproduction of inkjet imprints were analyzed: an indicator of the general contrast level (K), the value of color differences for the basic tone shades (ΔE), and the volume of the body color coverage (ΔE2). It was found that when printing on various types of corrugated cardboard, there is a general decrease in the overall contrast value. The actual level of color differences is ΔE=10...45 and exceeds the permissible standards for the color reproduction quality. This adversely affects the reproduction of different color tones in the printed image. In general, the quality of color reproduction differs for the test samples of corrugated cardboard in terms of the magnitude of the spread in the values of color distortions on the tone shades. The influence of the main characteristics of the investigated samples of corrugated cardboard on the quality indicators of inkjet printing has been analyzed. In particular, a significant influence of the index of color characteristics of the surface of corrugated cardboard L* and the type of corrugated board structure on the quality of color reproduction has been established. The study results reported here could make it possible to reasonably approach the selection of the corrugated board structure that is optimal in composition, increase the productivity of the technological process for manufacturing containers, and stabilize the quality of printing on corrugated cardboard

Исследование цветовых отличий при воспроизведении памятных цветов на устройствах визуализации

This work is devoted to the study of changes in color coordinates on various visualization devices during color reproduction, in particular smartphones, as one of the most commonly used devices in the modern world, which is associated with the hardware dependence of the color reproduction system. The purpose of the work is to select visualization tools, determine their technical characteristics, determine test colors for visualization on various devices, determine the tolerances in reproduction of each color when using various viewing devices. To achieve the goal, such tasks were set as the selection of images containing memorable colors. These colors are fundamental in determining the tolerances in color reproduction, since information about them is inherent in each person on the basis of his life experience and knowledge, and a change in the reproduction of memorable colors, a violation in color rendering, is the most visually noticeable. Memorable colors are converted into samples – test objects, which are used to determine coordinates in a device-independent color space. Determination of tolerances is made when changing color reproduction through the use of selective (color) correction. When solving the problem, it was noted that there are colors in which, with small changes in color coordinates, the visual component changes to a sufficiently strong degree, while other colors, with a numerically identical change, do not visually change. For the selected colors on various visualization tools, the difference in color reproduction is calculated and the calculations of color differences for different models of viewing devices with a visual difference in perception are given.

Automated Functional Color Field Tester (FCFTester) Trends and Reproducibility – A Multicenter Pilot Study

Background: The present study was designed to assess a protocol for investigating normative trends of kinetic color visual field sizes and reproducibility of such utilizing the Automated Functional Color Field Tester (FCFTester). Methods: The participants were recruited at three clinical sites. The participants were screened for the study based on a questionnaire designed by the authors to help assess the inclusion and exclusion criteria. There were 116 adult-only participants, however, only those reporting White race (n = 106) were used for statistical analysis. The mean age was 35.8 (std = 14) and nearly 70% of the sample was female. Results: This study demonstrated that kinetic visual field sizes across all four color isopters are not influenced by gender (p = 0.96) nor eye tested (p = 0.46). Only a slight difference in mean visual field sizes was found between the three clinical sites ranging from less than 2.5 degrees when the target was blue or green to less than 1.5 degrees for white or red targets. Overall, age had limited, yet significant, influence on kinetic field sizes likely related to the relatively young age of our participants. A significant difference in mean field size existed when comparing the four color isopters with an ascending order of green, red, blue, and white. This pattern was consistent across the three testing sites. Variability in field size for each color isopter was slight across the three clinical sites. Conclusion: The present pilot study shows promise that a protocol can be established to provide reproducible data and normative trends in kinetic color visual field testing. The authors recognize that this should be achievable with further refinement of the current testing protocol.

Drawing on Architecture: The Object of Lines, 1970–1990

Drawing on Architecture: The Object of Lines, 1970–1990

Smartphones&amp;#x2019; Skin Colour Reproduction Analysis for Neonatal Jaundice Detection

Abstract In recent years, smartphone-based colour imaging systems are being increasingly used for Neonatal jaundice detection applications. These systems are based on the estimation of bilirubin concentration levels that correlates with newborns’ skin colour images corresponding to total serum bilirubin (TSB) and transcutaneous bilirubinometry (TcB) measurements. However, the colour reproduction capacity of smartphone cameras are known to be influenced by various factors including the technological and acquisition process variabilities. To make an accurate bilirubin estimation, irrespective of the type of smartphone and illumination conditions used to capture the newborns’ skin images, an inclusive and complete model, or data set, which can represent all the possible real world acquisitions scenarios needs to be utilized. Due to various challenges in generating such a model or a data set, some solutions tend towards the application of reduced data set (designed for reference conditions and devices only) and colour correction systems (for the transformation of other smartphone skin images to the reference space). Such approaches will make the bilirubin estimation methods highly dependent on the accuracy of their employed colour correction systems, and the capability of reducing device-to-device colour reproduction variability. However, the state-of-the-art methods with similar methodologies were only evaluated and validated on a single smartphone camera. The vulnerability of the systems in making an incorrect jaundice diagnosis can only be shown with a thorough investigation of the colour reproduction variability for extended number of smartphones and illumination conditions. Accordingly, this work presents and discuss the results of such broad investigation, including the evaluation of seven smartphone cameras, ten light sources, and three different colour correction approaches. The overall results show statistically significant colour differences among devices, even after colour correction applications, and that further analysis on clinically significance of such differences is required for skin colour based jaundice diagnosis.

The impact of the Helmholtz-Kohlrausch effect on the appearance of near-white paper colours

This paper investigates the impact of the Helmholtz-Kohlrausch effect on near-white substrate colours. As the luminance of the test colour (or its simulated reflectance in a softproof setup) approaches that of the adapting white point the viewing mode changes from 'surface mode' to 'aperture mode', and the appearance of the test colour becomes self-luminous. However, some substrates with optical brighteners fall close to this threshold between viewing modes, since the OBAs not only increase the perceived reflectance but also increase the H-K effect, where it is very prominent in bluish colours. For graphic arts content shown on a display system, this essentially breaks the soft-proofing paradigm. The practical application of this work relates to cross-media colour reproduction, where the lightness appearance of some substrates is not adequately described by their colorimetric values, and this may impact on choice of proofing strategies.

Analysis of chromatic aberrations influence on operation of the tunable AOTF-based source

Developing a source with the possibility of tuning in wavelengths based on an acousto-optical tunable filter (AOTF), an essential factor is the ability to provide accurate color coordinates of the simulated color (in the case of developing a color standard for colorimetry) or the required wavelength (in the case of an application for spectral studies). As shown earlier, the choice of the principal layout – confocal or parallel beam path - primarily determines the dimensions and efficiency of using the luminous flux. However, these schemes also need to be analyzed for color or wavelength fidelity, considering other components used in the scheme. The analysis performed allows to identify the optimal scheme to ensure the required color reproduction accuracy and establish the requirements for correcting chromatic aberrations of the components.

Influence of Ink Curing in UV LED Inkjet Printing on Colour Differences, Ink Bleeding and Abrasion Resistance of Prints on Textile

Digital printing techniques are increasingly present in the field of textile printing. Particularly prominent is the inkjet printing technique using water-based inks, UV LED inkjet printing also increasingly being in use. UV LED inkjet is primarily not intended for direct clothing printing; however, it can be used especially as a hybrid solution in the soft signage market. It is a great option for the printers that are not engaged only in textile printing, and want a more versatile print portfolio, extending it to non-clothing textile products, e.g. soft signage and non-wearable products. As these types of products often require colour reproduction of logos, accurate colour reproduction, good ink adhesion and sharpness are important just like in other printing technologies. In order to evaluate the impact of UV LED radiation amount on colour differences, ink bleeding and abrasion resistance, six different fabric samples (five woven and one nonwoven) were printed using a UV LED inkjet printer. Based on the results of colour difference, it was established that a reduction of UV radiation (by half the manufacturer’s recommended amount) had no effect on this parameter. However, perceptible colour differences were observed with the use of different M measurement conditions defined by the international standard ISO 13655-2017. Reducing the amount of UV radiation had no effect on the adhesion and durability of the printed ink. Small differences detected in these two parameters were mainly a consequence of the properties of textile materials and not of decreased UV radiation.