CIELAB Space Research Articles

Performance of select color-difference formulas in the blue region.

The main objective of this work was to test the performance of major formulas for assessment of small suprathreshold color differences in the blue region. The models examined include CIELAB color space based equations, including CIELAB, CIE94, CIEDE2000, CMC (l:c), BFD (l:c), and formulas based on more uniform color spaces, such as DIN99d, CAM02-SCD, CAM02-UCS, OSA-GP, and OSA-Eu in comparison against data obtained via visual assessments. For this purpose, a dataset around the CIE high-chroma blue color center, hereafter called NCSU-B2, was developed. The NCSU-B2 dataset comprised 65 textile substrates and a standard, with a mean ΔE(ab)* color difference of 2.72, ranging from 0.54-5.72. Samples were visually assessed by 26 subjects against the reference gray scale in three separate trials with at least 24 h between assessments. A total of 5070 assessments were obtained. The standardized residual sum of squares (STRESS) index was used to examine the performance of various formulas for this dataset, as well as a previously developed NCSU-B1 low-chroma blue dataset [Color Res. Appl. 36, 27, 2011], and blue centers from other established visual datasets. Results show that formulas based on more recent uniform color spaces provide better agreement with perceptual data compared with models based on CIELAB space.

The influence of color grouping on users’ visual search behavior and preferences

The article investigates how the various colors and color pairs used as grouping factors affect the visual search process and direct manipulation activities in the context of toolbar-like graphical panels. Red, green, and blue colors having the same perceptual distance in the CIELab space are used. The results demonstrate significant influence of the examined color-related factors on the speed and accuracy. The color preattentive property depends strongly on the grouping pattern: layouts with smaller colored areas were operated worse than panels divided into larger parts. Meaningful differences were also observed between panels with single and two colored backgrounds.Preferences were examined by pairwise comparisons before and after performing the ‘search and select’ tasks. Subjective judgments were significantly differentiated by the toolbar background color pattern both prior to the performance tasks and after them. The initial relative weights structure changed decidedly after the performance experience being more consistent with the ‘search and select’ results. The location factor was irrelevant for the speed and accuracy as well as for preferences. Objective and subjective findings are compared and discussed. Linear regression models showing the preference structure change and the relationship between mean acquisition times and mean preference weights are developed and discussed.

The Image Recognition of Mobile Robot Based on CIE Lab Space

The image recognition of mobile robot is to extract the effective target information. The essence of image extraction is image segmentation. By extracting and distinguishing planar objects and three-dimensional objects, we propose two new algorithms. The color image is extracted by using CIE Lab Space. Then we propose a comparison method through the collection of two image samples. According to the principle of geometric distortion in the geometric space, we can easily distinguish the planar object in the environment. Therefore, Experimental results show that the combination of these two methods is accurate and fast in the color image recognition.

Research on the Color-Difference Evaluation of Food Package Printing Matter Based on the Human Visual Characteristics

In order to improve for the inadequacy of traditional evaluation methods, this paper researched a kind of color-difference evaluation method for the food package printing matter based on human visual characteristics. Research method is as follow: the reference image and the target image were transformed to the opposite color space, and were dealt with the human eye Contrast Sensitive Function (CSF) spatial filter. The modified three opposite color component of images were transformed into the CIE XYZ space image after CSF spatial filtering processed; finally the image was transformed to the CIELAB space image. The color-difference of the target image was calculated according to color-difference formula. The color-difference result of image is the calculation result with human visual characteristics filtering processed; it combines subjective evaluation with objective evaluation. The research could provide practical and effective evaluation method for the field of food package printing matter.

Perceptual color hit-or-miss transform: application to dermatological image processing

The hit-or-miss transform is a mathematical morphological processing designed to find objects in image. Its extension to grayscale domain is not unique, but Barat’s method is the most appropriate to find specific objects with bandwidth in space and color evolutions. This tolerance is possible with the use of non-flat structuring elements. In this paper, a color extension of the Barat’s method is presented. For this purpose, a new mathematical morphology method, based on the concept of convergence in the CIELAB space and where the definition of non-flat structuring elements is possible, is used. A comparison with the existing approaches in the literature is done. Results are given and commented on synthetic and real images.

Functional properties of sodium and calcium caseinate antimicrobial active films containing carvacrol

Active edible films were prepared by adding carvacrol into sodium caseinate (SC) and calcium caseinate (CC) matrices plasticized with two different glycerol concentrations (25 and 35wt%) prepared by solvent casting. Functional characterisation of these bio-films was carried out by determination of some of their physico-chemical properties, such as colour, transparency, oxygen barrier, wettability, dye permeation properties and antibacterial effectiveness against Gram negative and Gram positive bacteria. All films exhibited good performance in terms of optical properties in the CIELab space showing high transparency. Carvacrol was able to reduce CC oxygen permeability and slightly increased the surface hydrophobicity. Dye diffusion experiments were performed to evaluate permeation properties. The diffusion of dye through films revealed that SC was more permeable than CC. The agar diffusion method was used for the evaluation of the films antimicrobial effectiveness against Escherichia coli and Staphylococcus aureus. Both SC and CC edible films with carvacrol showed inhibitory effects on both bacteria.

Colour spaces effects on improved discrete wavelet transform‐based digital image watermarking using Arnold transform map

The most digital image watermarking algorithms have nearly always been realised in red, green and blue (RGB) colour space. In this study, a secure, robust and imperceptible CDMA image watermarking scheme which uses discrete wavelet transform is proposed and tested in eight colour spaces RGB, YCbCr, JPEG-YCbCr, YIQ, YUV, hue, saturation, intensity, hue, saturation, value and CIELab to determine which colour space is more effective in watermarking algorithms based on correlation techniques and provides a result which does not differ immeasurably from the original with respect to imperceptibility and robustness. In the proposed scheme, a scrambled binary image by Arnold transform map, after encryption, is embedded into sub-images of the first channel wavelet decomposition of intended colour space using block processing technique. The experimental results show that the proposed approach provides extra imperceptibility, security and robustness against JPEG compression and different noise attacks compared to the similar proposed methods in earlier works.

Log-Gabor Filters and Lda Based Facial Expression Recognition

This project introduces a tensor perceptual color framework (TPCF) for facial expression recognition (FER), which is based on information contained in color facial images. The TPCF enables multilinear image analysis in different color spaces, and demonstrates that color components provide additional information for robust FER. Using this framework, the components (in either RGB, YCbCr, CIELab space) of color images are unfolded to 2-D tensors based on multilinear algebra and tensor concepts, from which the features are extracted by Log-Gabor filters. The mutual information quotient method is employed for feature selection. These features are classified using a multiclass linear discriminant analysis classifier. The effectiveness of color information on FER using low-resolution and facial expression images with illumination variations is assessed for performance evaluation. Experimental results demonstrate that color information has significant potential to improve emotion recognition performance due to the complementary characteristics of image textures. Furthermore, the perceptual color space CIELab are better overall for FER than other color spaces, by providing more efficient and robust performance for FER using facial images with illumination variation.

CHARACTERIZATION OF COLOMBIAN QUESILLO CHEESE BY SPECTROCOLORIMETRY

Rationale: The colour of food is one of the major attributes which affect a consumer’s perception of its quality, and it is also a powerful tool for quality control and marketing. The Quesillo cheese is a typical Colombian cheese. The observed colour in Quesillo cheese is a composite of many contributing factors. Objectives: The objective of the current work was to characterize the colour of Quesillo cheese using parameters L*, a* and b* of the CIE (Commission Internationale d’Eclairage) system by spectrocolorimetry. Methods: The collection of data with colorimeters was used for the instrumental characterization of colour in Quesillo cheese. Colour parameters L*, a* and b* were measured in triplicate using CIE-LAB space for fourteen commercial Quesillo cheese and seven manufactured cheeses. Using the mean values of colour in the analysed cheeses, parameters of chroma metric (C*), hue (H*), colour differences (ΔE), whiteness index (WI) and yellowness indix (YI) were determined. Results: The general mean values obtained were, L*= 78.13, a*= -0.96, b* = 22.95, C*= 22.97 and H*= 92.38°. These can be estimated as the reference values for Quesillo cheese, which could be used in quality control in the manufacturing process. Different factors are discussed that can change or influence the colour in the final product. Conclusions:

DURABILITY OF TANNIN-BORON-TREATED TIMBER

Tannin-boron wood preservatives were investigated for their resistance against outdoor agents. This work focused on the analysis of the causes that affect the durability of the tannin-hexamine-treated samples. In particular, dimensional stability, resistance to leaching, and resistance to biological agents were investigated. The combined effect of deterioration agents was evaluated by subjecting the treated samples to simulated and natural weathering tests. The study of the appearance and of the color components (L*, a*, and b*) according to CIELAB space of the exposed samples was monitored to assess the efficacy of the tannin-boron formulations for outdoor applications. Significant resistance against the action of water (EN 84, ENV 1250-2) and insects (EN 47) has been demonstrated in specific tests. Conversely, the continuous stress due to artificial and natural weathering deteriorates the color and the visible features of the treated specimens. The combined effect of moisture modifications, solar exposition, and leaching cycles damages the structure of the tannin-based polymeric network and subsequently it negatively affects its preservation properties.

Dependence of the color appearance of some flowers on illumination

Seven flower colors perceived by five color experts using visual color measurement under 2800 K warm white fluorescent lamps, 3500 K plant growth lamps, and 6500 K light‐emitting diodes (LEDs) were compared with those under 6500 K fluorescent lamps, which represented illuminants in florist shops. Fluorescent lamps (6500 K, 1000 lx) were found to be effective for displaying flower colors and were used as the standard condition. The colors of flowers generally shifted in the same direction as those of the illuminants in CIELAB space. The color differences were highest under the 3500 K fluorescent lamp at both 500 and 2000 lx. At 500 lx, the ΔE values under the 6500 K LED were higher than those under the 2800 K lamp. The C* and ΔE values revealed that the 2800 K lamp was unsatisfactory for purple‐blue and purple flowers and was more suitable for floral displays at lower illuminance. Under the 3500 K lamp, the highest color distortion occurred in cool‐colored flowers, but C* increased for purple‐blue and purple flowers. The 6500 K LED tended to decrease C* for warm‐colored flowers under both illuminances, but it was effective for displaying purple‐blue and purple flowers with increased C*. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 28–36, 2014

Functional colored ceramic coatings obtained by thermal spray for decorative applications

Abstract Many inorganic pigments consist of a ceramic matrix doped with transition metal cations, which act as chromophore agents in the ceramic material and provide intense colors. Cassiterite and malayaite are the pigments most commonly used to replace pigments that contain cadmium in the ceramic industry, and are normally deposited using techniques such as CVD, sputtering, sol–gel and spray-pyrolysis. The aim of this study was to produce and characterize SnO 2 -based coatings for decorative applications employing a cost-effective technology (APS). The effects of spraying conditions on the crystallinity and microstructure of the coatings were studied. Tests revealed interesting results in terms of the structural features of the coatings, whose optical properties changed. The intrinsic color of the coatings was controlled and compared by reflectivity measurements in the CIELab space, and a change from red-pink to dark-gray was observed for the sample with the highest amount of amorphous cassiterite. The key factor seems to be the percentage of crystalline malayaite, which correlated with the redness value of the color space.

Multisource Classification of Color and Hyperspectral Images Using Color Attribute Profiles and Composite Decision Fusion

In this work, we treat the problem of combined classification of a high spatial resolution color image and a lower spatial resolution hyperspectral image of the same scene. The problem is particularly challenging, since we aim for classification maps at the spatial resolution of the color image. Contextual information is obtained from the color image by introducing Color Attribute Profiles (CAPs). Instead of treating the `R', `G', and `B' bands separately, the color image is transformed into CIE-Lab space. In this color space, attribute profiles are extracted from the `L' band, which corresponds to the Luminance, while the `a' and `b' bands, which contain the color information, are kept intact, and the resulting images are transformed back into RGB space. The spectral information is obtained from the hyperspectral image. A Composite Decision Fusion (CDF) strategy is proposed, combining a state-of-the-art kernel-based decision fusion technique with the popular composite kernel classification approach. Experiments are conducted, using simulated data and a real multisource dataset containing airborne hyperspectral data and orthophotographic data from a suburban area in Belgium. These experiments show that our CAPs perform well with respect to other approaches for extracting attribute profiles from high resolution color images, and that the proposed CDF strategy produces meaningful results with respect to concatenation and the highlighted state-of-the-art approaches for combining multisource data.

A note about the abnormal hue angle change in CIELAB space

Liu et al. [Color Res Appl 1995;20:245–250] compared the CIELAB hue angles under CIE illuminants D65 and A for quantifying the color appearance changes for gem materials. They found that CIELAB hue angle for some gem materials under illuminant D65 was larger than under A, which is contrary to the perceived blue and purple appearances under daylight and incandescent light sources, respectively. They called this phenomenon as the abnormal hue angle change in the CIELAB space for the gem materials. In this article, we note the proper way to quantify the appearance changes is to use chromatic adaptation transforms (CATs), since we are only concerning the color change of the illumination. At the same time, it is found that the chromatic adaptations in the sharper sensor space and in the cone fundamental space provide different results, the ones related to the latter being in better agreement with current blue‐to‐purple color appearance change. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 322–327, 2013

Lighting spectrum to maximize colorfulness

The spectrum of modern illumination can be computationally tailored considering the visual effects of lighting. We investigated the spectral profiles of the white illumination maximizing the theoretical limits of the perceivable object colors. A large number of metamers with various degrees of smoothness were generated on and around the Planckian locus, and the volume in the CIELAB space of the optimal colors for each metamer was calculated. The optimal spectrum was found at the color temperature of around 5.7×10(3) K, had three peaks at both ends of the visible band and at around 510 nm, and was 25% better than daylight and 35% better than Thornton's prime color lamp.

Adaptive color contrast enhancement for digital images

Noncanonical illumination that is too dim or with color cast induces degenerated images. To cope with this, we propose a method for color-contrast enhancement. First, intensity, chrominance, and contrast characteristics are explored and integrated in the Naka-Rushton equation to remove underexposure and color cast simultaneously. Motivated by the comparison mechanism in Retinex, the ratio of each pixel to its surroundings is utilized to improve image contrast. Finally, inspired by the two color-opponent dimensions in CIELAB space, a color-enhancement strategy is devised based on the transformation from CIEXYZ to CIELAB color space. For images that suffer from underexposure, color cast, or both problems, our algorithm produces promising results without halo artifacts and corruption of uniform areas.

Development of color density concept with color difference formulas in respect to human vision system

The aims of this study are to develop the color density concept and to propose the color density based color difference formulas. The color density is defined using the metric coefficients that are based on the discrimination ellipses and the locations of the colors in the color space. The ellipse sets are the MacAdam ellipses in the CIE 1931 xy-chromaticity diagram and the chromaticity-discrimination ellipses in the CIELAB space. The latter set was originally used to develop the CIEDE2000 color difference formula. The color difference can be calculated from the color density for the two colors under consideration. As a result, the color density represents the perceived color difference more accurately, and it could be used to characterize a color by a quantity attribute matching better to the perceived color difference from this color. Resulting from this, the color density concept provides simply a correction term for the estimation of the color differences. In the experiments, the line element formula and the CIEDE2000 color difference formula performed better than the color density based difference measures. The reason behind this is in the current modeling of the color density concept. The discrimination ellipses are typically described with three-dimensional data consisting of two axes, the major and the minor, and the inclination angle. The proposed color density is only a one-dimensional corrector for color differences; thus, it cannot capture all the details of the ellipse information. Still, the color density gives clearly more correct estimations to perceived color differences than Euclidean distances using directly the coordinates of the color space.

Goniocolorimetry: From measurement to representation in the CIELAB color space

AbstractThe classical definitions of color are well adapted to diffusing objects, whose color is almost independent of the viewing angle, and to very glossy object observed in the specular direction in respect to the light source. For glossy or iridescent objects, the color is difficult to characterize due to its dependence on the viewing direction. In order to cope with such objects and to represent their angle‐dependent colors in a colorimetric space, we adapt the CIELAB space to “goniocolorimetric” measurements. A crucial point when defining this space is the statement of the viewing solid angle. First, we suggest performing a BRDF measurement at high angular resolution in order to characterize the gloss of the specimen. Then, since for the definition of colors the CIE recommends cones of half‐angle of 2° or 10°, we propose to convert the measured BRDF into a reflectance factor defined in respect to these solid angles. This procedure is eased by a planar multispectral image of the BRDF, where solid angles are specified by the pixel size. At last, the reflectance factors are converted into CIELAB coordinates. By using this procedure, the perfect white diffuser but also the perfect mirror can be represented in this colorimetric space. © 2010 Wiley Periodicals, Inc. Col Res Appl, 36, 169–178, 2011;

Mean Shift Segmentation을 이용한 수채화 효과 생성 기법

본 논문에서는 영상처리에서 많이 사용하는 양방향 필터링(bilateral filtering)과 평균 이동 분할(mean shift segmentation)을 이용하여 일반적인 사진을 수채화 효과가 나도록 하는 리터칭 기법에 대하여 제안한다. 먼저 양방향 필터링을 이용하여 사진의 외곽선 부분은 보존하면서 고주파 성분을 약화시키도록 한다. 그리고 양방향 필터링된 영상에서 각각 DoG(Difference of Gradient) 에지 추출과 평균 이동 분할을 수행한다. 이때 DoG 에지 추출은 원영상의 RGB 색상 공간을 CIELAB 공간으로 변환 후 휘도(luminance) 성분만 이용하여 추출하도록 하며 두 결과를 결합하여 최종 영상을 생성한다. 본 논문에서 제안하는 기법으로 다양한 사진에 대하여 실험한 결과 수채화 효과가 잘 나타나는 것을 확인하였으며 특히 주광에서 촬영한 풍경 사진들에 대하여 보다 우수한 성능을 보임을 확인하였다. We propose a retouching method that converts a general photography to a watercolor painting image using bilateral filtering and mean shift segmentation which are mostly used in image processing. The first step is to weaken high frequency components of the image, while preserving the edge of image using the bilateral filtering. And after that we perform DoG(Difference of Gradient) edge extraction and mean shift segmentation respectively from the bilateral filtered image. The DoG edge extraction is performed using luminance component of the image whose RGB color space is transformed into CIELAB space. Experimental result shows that our method can be applied to various types of image and bring better result, especially against the photo taken in daylight.

Objective evaluation of color image fusion methods

A measure for objectively assessing the performance of color image fusion methods is proposed. Two different aspects are considered in establishing the proposed measure-namely, the amount of common information between the source images and the final fused image as well as the distribution of color information in the final image in order to achieve optimal color representation. Mutual information and conditional mutual information are employed in order to assess information transfer between the source images and the final fused image. Simultaneously, the distribution of colors in the final image is explored by means of the hue coordinate in the perceptually uniform CIELAB space. The proposed measure does not depend on the use of a target-fused image for the objective performance evaluation. It is employed experimentally for objective evaluation of fusion methods in the cases of medical imaging and night vision data.