Original Color Research Articles

Relationships between colorization and pseudo-colorization of monochrome images

This paper investigates the relationship between colorization and pseudo-colorization techniques for converting grayscale images to color. Colorization strives to create visually believable color versions of monochrome images, either replicating the original colors or generating realistic, alternative color schemes. In contrast, pseudo-colorization maps grayscale intensities to pre-defined color palettes to improve visual appeal, enhance content understanding, or aid visual analysis. While colorization is an ill-posed problem with infinitely many RGB solutions, pseudo-colorization relies on mapping functions to deterministically assign colors. This work bridges these techniques by exploring the two following operations: first - deriving pseudo-color from colorized images - this allows for creating stylized or abstract representations from existing colorizations, and second - enriching color diversity in pseudo-colored images - this enhances visual appeal and attractiveness of pseudo-colored images. The paper emphasizes the centrality of decolorization (rgb-to-gray) models in both processes. It focuses on the theoretical underpinnings of these problems but complements them with illustrative examples for clarity.

Physically Based Rendering of Animated Point Clouds for EXtended Reality

Abstract Point cloud 3D models are gaining increasing popularity due to the proliferation of scanning systems in various fields, including autonomous vehicles and robotics. When employed for rendering purposes, point clouds are typically depicted with their original colors acquired during the acquisition, often without taking into account the lighting conditions of the scene in which the model is situated. This can result in a lack of realism in numerous contexts, especially when dealing with animated point clouds used in eXtended reality applications, where it is desirable for the model to respond to incoming light and seamlessly blend with the surrounding environment. This paper proposes the application of physically based rendering (PBR), a rendering technique widely used in real-time computer graphics applications, to animated point cloud models for reproducing specular reflections, and achieving a photo-realistic and physically accurate look under any lighting condition. To achieve this, we first explore the extension of commonly used animated point cloud formats to incorporate normal vectors and PBR parameters, like roughness and metalness. Additionally, the encoding of the animated environment maps necessary for the PBR technique is investigated. Then, an animated point cloud model is rendered with a shader implementing the proposed PBR method. Finally, we compare the outcomes of this PBR pipeline with traditional renderings of the same point cloud produced using commonly used shaders, taking into account different lighting conditions and environments. Through these comparisons, we demonstrate how the proposed PBR method enhances the visual integration of the point cloud with its surroundings. Furthermore, it will be shown that using this rendering technique, it is possible to render different materials, by exploiting the features of PBR and the encoding of the surrounding environment.

Palmar reconstruction using full-thickness skin grafts from the groin and lateral malleolus regions: A comparison of long-term outcomes.

Using the skin of the lateral malleolus region for reconstruction of smaller areas of the palm may yield better outcomes than using the skin of the groin region. However, no previous study has provided long-term data comparing the groin and lateral malleolus regions as donor sites for full-thickness skin grafts (FTSGs) in palmar reconstruction. Therefore, this study aimed to compare the groin and lateral malleolus regions as donor sites for FTSGs in palmar reconstruction over a long-term follow-up period. The patients were classified into groin and lateral malleolus region groups (n = 15 each). Measurements were obtained at the graft site, the contralateral site corresponding to the graft site, and the donor site. A chromameter was used to measure skin color, and the Patient and Observer Scar Assessment Scale (POSAS) was used to evaluate the scar at the skin graft site. Compared to the groin region group, the lateral malleolus region group showed skin colors that were closer to the original color of the palm in terms of lightness and red/green values. Additionally, the lateral malleolus region group received better esthetic ratings in the POSAS. Our results revealed that using the lateral malleolus region for FTSGs in palmar reconstruction resulted in better outcomes than using the groin region, even over a long period.

Extraction of Soluble Salts and Iron Sulfides from the Wood of the “Huaguangjiao I” Shipwreck

Shipwreck wood often contains soluble salts and iron sulfides, which pose a threat to its stability. Therefore, desalination treatment must be carried out during protection. In this study, deionized water and ethylene diamine tetraacetic acid disodium salt (EDTA-2Na) solution were used to extract soluble salts and iron sulfides from the 511 wood components of the “Huaguangjiao I” shipwreck. The extraction lasted for 1120 days, during which extraction progress was monitored by measuring the electrical conductivity and iron content of the soaking solution. The results indicated that the extraction experiment reached its endpoint when the conductivity of the soaking solution was maintained at 80~100 μs/cm and the iron content was maintained at 8~15 mg/L. More than 143.35 kg of iron were extracted from the wood of the “Huaguangjiao I” shipwreck. After extraction, the content of soluble salt ions in the wood were less than 5 μg/g, with an iron content below 5%. The wood has returned to its original color and with a certain degree of degradation. “Huaguangjiao I” was the first large-scale marine shipwreck to complete the desalination treatment of all wooden components. This study provides guidance for the desalination treatment of large-scale wooden shipwrecks.

Visual Features for Improving Endoscopic Bleeding Detection Using Convolutional Neural Networks.

The presented paper investigates the problem of endoscopic bleeding detection in endoscopic videos in the form of a binary image classification task. A set of definitions of high-level visual features of endoscopic bleeding is introduced, which incorporates domain knowledge from the field. The high-level features are coupled with respective feature descriptors, enabling automatic capture of the features using image processing methods. Each of the proposed feature descriptors outputs a feature activation map in the form of a grayscale image. Acquired feature maps can be appended in a straightforward way to the original color channels of the input image and passed to the input of a convolutional neural network during the training and inference steps. An experimental evaluation is conducted to compare the classification ROC AUC of feature-extended convolutional neural network models with baseline models using regular color image inputs. The advantage of feature-extended models is demonstrated for the Resnet and VGG convolutional neural network architectures.

A versatile CuCo@PDA nanozyme-based aptamer-mediated lateral flow assay for highly sensitive, on-site and dual-readout detection of Aflatoxin B1

Mycotoxin contaminations in food and environment seriously harms human health. Constructing sensitive and point-of-test early-warning tools for mycotoxin determination is in high demand. In this study, a CuCo@PDA nanozyme-based aptamer-mediated lateral flow assay (Apt-LFA) has been elaborately designed for on-site and sensitive determination of mycotoxin Aflatoxin B1 (AFB1). Benefiting from the rich functional groups and excellent peroxidase-like activity, the CuCo@PDA with original dark color can be conjugated with the specific recognition probe (i.e., aptamer), generating colorimetric signal on the test lines of Apt-LFA via a competitive sensing strategy. The signal can further be amplified in-situ by catalytic chromogenic reaction. Therefore, a visual and dual-readout detection of AFB1 has been realized. The developed Apt-LFA provides a flexible detection mode for qualitative and quantitative analysis of AFB1 by naked-eyes observation or smartphone readout. The smartphone-based LFA platform shows a reliable and ultrasensitive determination of AFB1 with the limit of detection (LOD) of 2.2 pg/mL. The recoveries in the real samples are in the range of 95.11–113.77% with coefficients of variations less than 9.84%. This study provides a new approach to realize point-of-test and sensitive detection of mycotoxins in food and environment using nanozyme-based Apt-LFAs.

Dyeing of doyo fiber (Curculigo latifolia) using teak leaf extract (Tectona grandis) as a natural coloring material

The Dayak Benuaq tribe uses natural dyes to give color to the Ulap Doyo woven fabric made from an endemic plant, namely Doyo (Curculigo latifolia). The purpose of this study was to carry out the extraction process and identify the phytochemical compounds in teak leaves, to carry out the fixation process on doyo fiber that had been treated with mordant, to measure the color fastness on doyo fiber. The extraction process uses the decoction method with 1 L distilled water as a solvent. Phytochemical testing using a UV-Vis Spectrophotometer. Brightness and color discoloration were measured using the Colorimeter WR10 FRU. The test results show teak leaves have the potential as a red natural dye on doyo fiber. The phenol content contained in the teak leaf extract solution was 29.46 GAE/mg extract. Then the flavonoid content contained was 3.74 µg CE/mg extract. Furthermore, the anthocyanin content contained was 0.181 mg/g extract. lime (CaCO3) mordant is to maintain the original color, the alum (Al2(SO4)3) mordant is to increase the brightness of the colors, and the tunjung (FeSO4) mordant is to give a dark color to the doyo fibers. Color fastness with dye heat testing (40°C) showed color direction values is good/4.

Thin colorimetric film array for rapid and selective detection of v-type nerve agent mimic in potentially contaminated areas

The expeditious detection and quantification of V-series nerve agents (VX) on potentially contaminated surfaces are crucial for the prevention of regional conflict incidents, acts of terrorism, or illicit activities. However, the low volatility and high toxicity of VX make these tasks challenging. Herein, we designed two novel colorimetric thin polymeric films to rapidly and sensitively detect demeton-S, a VX mimic, in contaminated areas. The polymeric films were specifically engineered to include a coordination site for Au (III) ions. Initially, these films were coordinated with Au (III), causing a discernible alteration in color due to enhancement in intramolecular charge transfer process. In the presence of demeton-S, the Au (III) ligands in the films are displaced with demeton-S, resulting in the restoration of the original color of the film, as the enhanced intramolecular charge transfer process is inhibited and thereby serving as an indicator of the presence of demeton-S. The polymeric films exhibit remarkable selectivity toward demeton-S compared to G-type nerve agents and other interference. The reusability of the polymeric films for demeton-S detection was achieved owing to the reversibility of the films during the alternative exposure of Au (III) and demeton-S. The polymeric films demonstrated their applicability for demeton-S detection and quantification in several contaminated areas, including different water, soil, and skin, rendering them highly suitable for on-site measurements.

A novel sulfhydryl-modified superparamagnetic photonic crystal sensing material for the simultaneous heavy metal ions detection and adsorption treatment

A novel superparamagnetic photonic crystal (Fe3O4@SiO2@Sulfhydryl SPC) was successfully created for simultaneous visual detection and absorption of harmful heavy metal ions. This SPC was made by combining photonic crystal and superparamagnetic nanosphere technologies. During detection, Fe3O4@SiO2@Sulfhydryl nanospheres can move in the liquid sample and fully absorb the target substances. The detection range is from 1 μg/L to 5 mg/L, which corresponds to the critical concentration range for heavy metal ions in drinking water and sewage. The detection limit is 1 μg/L. In the detection process, the signal responded rapidly and remained stable when analyzed with a fiber optic spectrometer. Notably, the signal intensity decreased significantly, with a reduction of 62.22 a.u. for Hg2+ and 124.31 a.u. for Ag+. Simultaneously, the visual results were striking. The SPC changed color from orange (PC structural color) to the original reddish-brown color of the solution with the formation of magnetic aggregates (PC structural color disappeared). This SPC exhibits excellent sensitivity, offers a clear visual display, possesses strong absorption detection capabilities, is easy to use, cost-effective, and, importantly, does not cause secondary pollution. Furthermore, the harmful heavy metal ions absorbed by the SPC can be easily removed from the water sample using an external magnetic field, overcoming challenges related to efficient separation of the adsorbent material from wastewater. As a result, this SPC holds great promise for real-time visual monitoring and practical sewage purification processes.

An RGB Pseudo-Colorization Method for Filtering of Multi-Source Graphical Data

Artificial colorization (pseudo-colorization) is a commonly used method to improve the readability of images obtained from sources (sensors) that do not reflect the original color of the object of observation (e.g., X-ray). It is designed to draw the observer’s attention to the important details of the analyzed image (e.g., disease changes in medical imaging). Analogous needs occur in the process of assessing the emission security (EMSEC) of imaging devices used to process classified information, which is made on the basis of the analysis of images reproduced from compromising emanations related to the operation of these devices. The presence of many graphic elements in an image may reduce the level of perception of the information contained in it. Such images may be very noisy or contain overlapping graphic symbols, the source of which is devices processing graphic information operating in close proximity to each other. The use of various types of measures enabling data filtration at various stages of their processing, e.g., the use of a directional antenna, frequency filtering, point filtering or contextual contrast modification, does not always prove effective. The solution to the filtration problem is the pseudo-colorization of the image. However, the image colorization used based on the typical “Hot”, “Radar” or “Cold” color palettes does not meet the requirements for filtering graphic data from many sources. It is necessary to use a filter that will allow the sharp cut-off of graphic data at the border between the background and the graphic symbol. For the pseudo-colorization process itself, the exponential function as a function of transforming the amplitudes of image pixels from the gray color space to the RGB color space is sufficient. However, the smooth transition of the function shape from zero values to values greater than zero results in a low efficiency of filtering graphic data from noise. In this article, a method of filtering an image based on the pseudo-colorization of its content, i.e., reproduction of a compromising emanation signal level in the RGB value of image pixel color components, was proposed. A quadratic function was proposed as the transformation function. The higher effectiveness of the method based on the use of a square function (compared to the exponential function) was shown by conducting tests on many images, some of which are presented in this article. The proposed solution is a universal approach and can be used in various fields related to image analysis and the need for their filtration. Its universality is related to the possibility of changing function parameters affecting its position on the value axis from 0 to 255, its width, its minimum and its maximum value for each RGB channel.

«Rimpiango proprio che l’umidità m’abbia per sempre guastata una fotografia». Elio Modigliani, le fotografie dell’isola di Nías (1886-1889) e la colorazione automatica di immagini antropologiche. Spunti e ricerche

Elio Modigliani collected images from the island of Nías, which he then published in A journey to Nías (1890). Many of these images refer to materials held and exhibited by the Museum of Anthropology and Ethnology of the University of Florence. Here we conducted some trials on the use of artificial intelligence (AI) not only to colorize them, but also to retrieve information from the images useful for restoration and conservation. Modigliani's photographs are of particular interest. They illustrate and integrate his reflections on the use of photography for anthropological field research, offer valuable information on shooting techniques and on the original condition and colors of the artifacts. Although AI may not always reconstruct with absolute fidelity the original colors, especially for clothing, our results provides important guidelines for analysis and allows a cogent discussion of the possibilities of AI technology in anthropological research.

New dispersions for pigment printing binders in the manufacture of light industry goods

Pigment printing using screen technology has certain problems associated with the limited use of domestic raw materials. The expansion of the range of printing inks fills the need for small-circulation production of textile products with original artistic and color design and the use of modern printing equipment. In this work, the possibility of using new aqueous polyurethane dispersions as binders in pigment printing was explored for the first time. This will expand the range of thickeners through the use of polyurethane dispersions, ensuring the production of strong and elastic polymer films during low-temperature processing. Such dispersions are environmentally friendly products, since toxic solvents are not used. We propose the application of new polyurethane thickeners in compositions with polyurethane dispersions as a rheological modifier. The rheological parameters of printed compositions and the physical and mechanical properties of films of polyurethane dispersions were determined and it was found that the dispersions used are capable of forming a soft and plastic film. This confirms the suitability of these film-forming preparations for use in pigment printing. The new binders based on polyurethane dispersions make possible to create effective printing compositions, to improve the quality of prints and to impart improved performance properties.

Visual mental imagery of atypical color objects attracts attention to an imagery-matching object.

Mental imagery attracts attention to imagery-matching stimuli. However, it remains unknown whether voluntarily imagined atypical color also attracts attention to a stimulus that matches the imagery when the imagined stimuli are color-diagnostic objects, which are strongly associated with typical color. This study investigated whether people can voluntarily imagine atypical colors of such objects and attend to imagery-matching stimuli. Participants in the imagery group were instructed to imagine an atypical color of the black-white objects according to the instructed color or voluntarily selected color, whereas participants in the control group were instructed to attend to the objects without any instruction of imagery. Thereafter, they detected a color target in a visual search task. Results revealed that participants in the imagery group directed attention to the imagery-matching atypical color, not to the original color of the object in the search. Meanwhile, participants in the control group did not demonstrate any attentional guidance. These results suggest that voluntarily imagining atypical color can attenuate mental representations of the original color imagery and change attention to a stimulus that matches imagery.

Effect of the spatial location of boundary on colour overflow in Gamut conversion

The colour gamut is an important indicator of the colour performance of a terminal display. Due to the variety of gamut standards and display devices, it is often necessary to convert the gamut to achieve a standardised display when using a terminal to display an image, but gamut conversion can lead to many problems such as colour overflow. This paper examines the problem of colour overflow in gamut conversion for terminal displays. First, a gamut model of the terminal display is established based on the CIE colorimetric principles, and the gamut conversion principles are briefly described based on the gamut model. Secondly, the geometric representation of the gamut boundary surface is obtained by Bessel fitting of the gamut boundary. On this basis, the geometric relationship between the boundary surface of the target colour gamut and the original colour gamut is analysed, the causes and conditions of overflow are analysed, and the overflow ratio is calculated to provide theoretical guidance for the correction of colour overflow in the process of colour gamut conversion of the display terminal.

ARiRTN: A Novel Learning-Based Estimation Model for Regressing Illumination.

In computational color constancy, regressing illumination is one of the most common approaches to manifesting the original color appearance of an object in a real-life scene. However, this approach struggles with the challenge of accuracy arising from label vagueness, which is caused by unknown light sources, different reflection characteristics of scene objects, and extrinsic factors such as various types of imaging sensors. This article introduces a novel learning-based estimation model, an aggregate residual-in-residual transformation network (ARiRTN) architecture, by combining the inception model with the residual network and embedding residual networks into a residual network. The proposed model has two parts: the feature-map group and the ARiRTN operator. In the ARiRTN operator, all splits perform transformations simultaneously, and the resulting outputs are concatenated into their respective cardinal groups. Moreover, the proposed architecture is designed to develop multiple homogeneous branches for high cardinality, and an increased size of a set of transformations, which extends the network in width and in length. As a result of experimenting with the four most popular datasets in the field, the proposed architecture makes a compelling case that complexity increases accuracy. In other words, the combination of the two complicated networks, residual and inception networks, helps reduce overfitting, gradient distortion, and vanishing problems, and thereby contributes to improving accuracy. Our experimental results demonstrate this model's outperformance over its most advanced counterparts in terms of accuracy, as well as the robustness of illuminant invariance and camera invariance.

Early modern knitted caps (fifteenth to sixteenth centuries): analyzing dyes in archaeological samples using microspectrofluorimetry complemented by HPLC–MS

The knitted cap was the ubiquitous and most visible garment men wore throughout early modern society, from apprentices to royals. Documentary evidence also suggests that red was a conventional color for specific garments in the sixteenth century, including knitted caps. However, most knitted caps in museum collections are now a muddy brown characteristic of archaeological textiles, and their original color has seldom been studied. Considering the potential of microspectrofluorimetry for analyzing dyes in ancient textiles and manuscript illuminations, this technique was tested on six caps dating from the fifteenth to sixteenth centuries examined in the Knitting in Early Modern Europe research project. The colors are in good preservation condition in two samples, whereas the others show extensive degradation. The emission and excitation spectra acquired allowed the identification of the similarities and differences between samples, grouping them into different dye sources such as cochineal-based and madder-based (RED1 and RED2, respectively). For the coif cap and split-brimmed cap in good condition, analysis through HPLC–MS confirmed the sources of the dyes as Rubia tinctorum and cochineal. It also disclosed the source for another coif cap as Kermes vermilio (RED4). The other knitted items are possibly madder-based (RED3), but HPLC–MS did not allow confirmation of the madder source. The continuing development of a database of excitation and emission spectra acquired from historical textiles, such as the knitted caps, will support the identification of dye sources and specific formulations. Although this technique demands a comprehensive database of references for comparison with the complex signals identified, it allows for rapid spectra acquisition, providing tremendously valuable information.

Accelerated thermal aging of Kraft papers impregnated with dielectric liquids

Accelerated thermal aging was conducted on Kraft papers impregnated with mineral insulating oil (MO) and palm insulating oil (PO), and the effect of aging time on the oils and Kraft papers was observed. Each sample consisted of insulating oil, dried Kraft paper, and weighed metal catalysts (copper, iron, zinc, and aluminum) in a bottle. Prior to aging, the bottles were left for 24 h at room temperature for impregnation to take place. The thermal aging experiments were carried out at 130 °C for 250, 500, and 750 h. The properties of the MO and PO (moisture content, acidity, and ultraviolet-visible absorption spectra) and the properties of the Kraft papers (tensile strength and colour) were determined. Results showed that the aged PO had higher moisture content compared with the aged MO. However, the Kraft papers impregnated with PO had better tensile strength after 750 h of aging, which may be attributed to the affinity of PO to moisture. This slows down the hydrolytic degradation mechanism. In terms of colour, the Kraft papers were darker than their original colour as the tensile strength decreased. To conclude, the Kraft paper impregnated with PO had higher tensile strength compared with those impregnated with MO.

Comparison of different drying techniques for Zanthoxylum bungeanum leaves: Changes in color, microstructure, antioxidant capacities, and volatile components

Herein, the effects of different drying methods, namely, indoor natural drying (ND), vacuum freeze drying (FD), vacuum drying (VD), hot air drying (AD), and heat-pump drying (PD) on the qualities of Zanthoxylum bungeanum leaves were investigated. The VD-treated Z. bungeanum leaves retained their original color to a greater extent. The microstructure was significantly affected by the temperature, as evidenced by scanning electron microscopy. In addition, FD, and AD both led to high and relatively similar contents of the various components, including the total phenols, flavonoids, proteins, and sugars. The strongest antioxidant capacities resulted from AD treatment, with total phenolic and flavonoid contents as high as 65.07 mg GAE/g dw and 133.2 mg RE/g dw, respectively. Moreover, 107 volatile organic compounds (VOCs) were identified using headspace solid-phase microextraction–mass spectrometry coupled with gas chromatography–mass spectrometry and classified into eight types according to their structures. The different drying methods were found to produce variations in the number and relative contents of the VOCs, which were mainly olefins and alcohols. A comprehensive evaluation of the economic value and product quality concluded that AD is the most suitable drying method for Z. bungeanum leaves, owing to its high efficiency, low cost, and good product quality.

Effects of ultra-high pressure, thermal pasteurization, and ultra-high temperature sterilization on color and nutritional components of freshly-squeezed lettuce juice

The aim of this study was to evaluate the effects of ultra-high pressure (UHP, 600 MPa/2 min), thermal pasteurization (TP, 95 °C/1 min) and ultra-high temperature (UHT, 115 °C/5 s) sterilization on the color, sensory evaluation, microorganisms, physicochemical characteristics and nutritional components of freshly-squeezed lettuce juice (FLJ). Results showed that three sterilization methods demonstrated desirable inactivation effects on total aerobic bacteria, yeast and mold, and there were no significant changes in the main nutritional components, including ash, protein, carbohydrate and total dietary fiber. However, UHT and TP significantly affected the color of FLJ from bright green to light brown and made chlorophyll, β-carotene and vitamins (VE, VC, VK1, VB6, VB12, and folic acid) contents markedly decreased. By contrast, UHP maintained the original color, fresh-like sensory qualities, vitamins, and carotene of FLJ to the greatest extent. Our results provide a promising application of UHP in the large-scale processing of FLJ.

Exploring alternatives for securing anatomical structures in capturing digital images: A comparative analysis.

Teaching veterinary anatomy using digital platforms requires improved image quality, which may influence the fixation process. This study aimed to compare four embalming solutions for high-colour-quality images of different tissues compared to the original image. Four equine left pelvic limbs were cut into metameres and divided equally for application of 10% formaldehyde, 96% glycerine, 33% hypersaturated NaCl solution and modified Larssen solution, respectively, which was maintained for 3 days. After drying for 3 days at room temperature, photographs were obtained at time 0 (T0), without any fixation process (original colour); time 1 (T1), immediately after removal from the solutions; and every 24 h for 3 days (T2-T4). The image colour quality was investigated by digitally evaluating the cortical bone, tendon and bone marrow using histograms and CIEDE2000 as well as by 10 specialists in an online survey. CIEDE2000 and histograms revealed that all fixation solutions changed the original tissue colour at all the time points (p < 0.0001). According to the specialists, the 33% saline solution produced the best results compared to the original one. The modified Larssen solution demonstrated better results for the tendon, marrow and cortical bone at T3 (p = 0.0015). Considering the colour of digital images, the modified Larssen solution provided the best results; however, the visual evaluation by the specialists revealed the 33% saline solution as the best.