Large Color Differences Research Articles

A pilot study on evaluating common appearance and a colour naming approach to measure it

If an image, for example a company logo is shown on different devices the degree of colour consistency amongst this set of stimuli can be defined as common appearance (CA). Because of the expanding number of devices with high dynamic range of imaging and with highly varying colour gamuts this issue becomes more and more important. Unfortunately conventional and established colourimetry, where usually two patches or images are compared side by side or through a media relative approach, is not sufficient, because the used metrics are developed for small colour distances. Establishing a measurement-tool for large colour differences and multiple reproductions side by side requires approaches that go beyond classic colourimetry. In this paper we designed a psychophysical experiment to measure if CA can be measured and we show a first approach for establishing a metric for CA through colour naming.

Color Difference Evaluation for Digital Pictorial Images Using the Magnitude Estimation Method

A new set of color difference data using complex images was collected including small and large color differences. Using 13 images, 182 test images were generated to have various average lightness, chroma or hue values compared to the original images. Twenty observers estimated the overall color difference between the reference and manipulated images shown on an sRGB monitor with 250 cd/m2 as a peak white in a dark room. The magnitude estimation technique was adopted for the visual assessment. The parametric factors of CMC(l:c), and CIEDE2000(l:c) were optimized using the color difference data set. Results showed that CIEDE2000 performs better than CMC. The best ratio for CMC(l:c) is (4:3), while (3.5:1) is the best for CIEDE2000(l:c) for overall color difference prediction.

Introducing WLab—Going from Wpt (Waypoint) to a uniform material color equivalency space

AbstractA set of invertible non‐linear transforms was derived that adjusts Wpt (Waypoint) coordinates (based on Wpt normalization) to and from a perceptually more uniform coordinate system (WLab or Waypoint‐Lab) than that provided by Wpt that allows for the advantageous features of Wpt to be directly applied to situations where other standard color spaces are typically used. The proposed transformations were found by optimizing for perceptual uniformity over both large and small color difference scales. The Munsell color order system was used as a representation for optimizing large‐scale perceptual uniformity. Correlations with Munsell value, chroma and hue along with comparisons with CIELAB and CAM02‐UCS were used to correct and assess overall large‐scale uniformity. The ΔE*94 color difference formula was used for optimization purposes for small‐scale uniformity. A STRESS analysis was applied to compare color differences based on Euclidean WLab distances with color differences based upon ΔE*ab, ΔE*94, ΔE00, DIN99o, CIECAM02, and CAM02‐UCS. It was found that WLab is a reasonably uniform material color equivalency space with small Euclidean WLab distances not being statistically different from ΔE*94, ΔE00, and Euclidean distances of DIN99o and CAM02‐UCS under reference observing conditions. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 550–563, 2015

A Similarity Measure for Large Color Differences

Hundreds of large color differences, of magnitude 20 ΔE00, were generated and used in a visual sorting experiment. The process of generating these color differences and two specific experiments are described in detail. The results show that small color difference metrics, such as ΔE00, do not consistently model the visually sorted differences for large differences. A new similarity measure, based on a cosine similarity between categorical vectors of colors, is described and used to more consistently model large color differences. This similarity metric can be used to better characterize large color errors during reproduction, for image processing operations such as segmentation or as a feature for content retrieval. The new measure can also be applied to visual phenomena, such as categorical perception, in which within category color differences are perceived as smaller than across category differences.

국내 시판 생막걸리의 이화학적 특성

This study was examined the quality characteristics of 20 types of non-sterilized commercial Makgeolli. These samples are classified according to firm size, enterprise Makgeolli(4 samples), prize-winning Makgeolli(6) and local Makgeolli(10). The alcohol contents of Makgeolli was determinded as follows: enterprise Makgeolli(6.18%), local Makgeolli(7.11%), and award-winning( 7.87%). Enterprise Makgeolli(0.24%) showed higher total acidity than award-winning and local Makgeolli(0.21%). In addition, pH levels were as follows: local Makgeolli(3.75), award-winning Makgeolli(3.77), and enterprise Makgeolli(4.09). Enterprise Makgeolli had the lowest sugar content. According to the sensory evaluation, three grades were identified based on balance and taste(5 points). The upper grade(more than 3 points) showed a higher pH, reducing sugar, higher aminoacidity, more soluble solids, and larger color differences than other grades. There were no significant differences in the level of acidity across the grades. The alcohol and volatile acid contents of the upper grade were lower than the middle(2.0-2.9 points) and lower(under 2.0 points) grades. Further research should provide a quality analysis of leavening agents and fermentation conditions, and a sensory evaluation.

Illuminant estimation for color constancy: why spatial-domain methods work and the role of the color distribution.

Color constancy is a well-studied topic in color vision. Methods are generally categorized as (1) low-level statistical methods, (2) gamut-based methods, and (3) learning-based methods. In this work, we distinguish methods depending on whether they work directly from color values (i.e., color domain) or from values obtained from the image's spatial information (e.g., image gradients/frequencies). We show that spatial information does not provide any additional information that cannot be obtained directly from the color distribution and that the indirect aim of spatial-domain methods is to obtain large color differences for estimating the illumination direction. This finding allows us to develop a simple and efficient illumination estimation method that chooses bright and dark pixels using a projection distance in the color distribution and then applies principal component analysis to estimate the illumination direction. Our method gives state-of-the-art results on existing public color constancy datasets as well as on our newly collected dataset (NUS dataset) containing 1736 images from eight different high-end consumer cameras.

Extracting Golden Area from Image Based on Otsu Algorithm

The paper suggested an algorithm to extract the golden region with tone change in an image as a printing plate information of metallic ink. It is based on HSV color space. A statistical hue range of golden color was used to separate the golden regions from the image, and Otsu algorithm was applied to acquire the tone of golden regions. The golden target regions are acquired by multiplication pixel by pixel between processed H values and the processed S values. The experiments were carried out on various images with different textures and background characteristics, and the segmentation effect were compared and analyzed also. They showed that the suggested algorithm is suitable for both simple and complex texture area. The color difference between image’s background and target influences the result of extraction, he large color difference is more suitable for segmentation.

Geometrical structure of perceptual color space is affine

Color spaces (e.g., CIE, Macleod-Boynton, and CIELUV) are invaluable for specifying colors. However, CIE and M-B space only predict which spectral distributions will match, while CIELUV deals with the discrimination of small color differences. There is much more to color perception than matching and discrimination. For example, similarities between colors (Zaidi & Bostic, 2008) and between color changes (Zaidi, 1998) can be used to identify materials across illuminants. Uniform color spaces based on multi-dimensional scaling of similarity ratings do exist, but these rely on Euclidean assumptions shown to be untenable (Wuerger, et al, 1995). We investigated the geometrical structure underlying relative similarity judgments. In a metric space, the distance between chromaticities would represent their magnitude of similarity, but even in a weaker affine space, ratios of distances between colors on a line would provide measures of relative similarity, and parallelism would define similarity between color changes. We tested whether affine geometry holds for a mid-point setting task. We chose two large quadrilaterals in the M-B equiluminant color plane. On each trial, observers viewed three colored patches, two of which were the endpoint colors forming one side of the quadrilateral. Observers were instructed to consider the color change between the test patches in terms of "reddish-greenish" and "bluish-yellowish" components and to set the color of the middle patch, by adjusting its hue and saturation, to the combined midpoint of the change on the two dimensions. After finding the mid-point for the four sides, observers set the midpoints between the two pairs of facing mid-points. For four observers, the two final mid-points for each quadrilateral coincided, thus satisfying Varignon’s Theorem and passing the affine test. A perceptual color space based on relative similarities across large color differences thus has an affine structure. Meeting abstract presented at VSS 2013

A high quality color imaging system for computerized tongue image analysis

In order to improve the quality and consistency of tongue images acquired by current imaging devices, this research aims to develop a novel imaging system which records human tongue information faithfully and precisely for medical analysis. A thorough demand analysis is firstly conducted to summarize requirements for reliable rendering of all possible medical clues, i.e., color, texture and geometric features. Then a series of system design criteria are illustrated accordingly, and by following them, three hardware modules of the imaging system, including illuminant, lighting path and imaging camera, are optimally proposed. Moreover, one built-in software module, the color correction process, is also provided to compensate color variations caused by system components. Finally, several important performance indicators, including illumination uniformity, system reproducibility and accuracy, are elaborately tested. Experimental results show that captured images are in high quality and keep stable when acquisitions are repeated. The largest color difference between any two acquired images is 1.6532, which is hardly to be distinguished by human observation. Compared to existing devices, the proposed system could provide much more accurate and stable solution for tongue image acquisition. Besides, this developed imaging system has been evaluated by doctors of Traditional Chinese Medicine for almost three years and over 9,000 tongue images have been collected, analysis results based these data also validate the effectiveness of the proposed system.

Colour Separation and Aversion

Aversion to achromatic patterns is well documented but relatively little is known about discomfort from chromatic patterns. Large colour differences are uncommon in the natural environment and devi...

Color Processing Methods of Different Seasonal SPOT5Images before Mosaic

With only few images for choice,how to mosaic images of different seasonal and produce good mosaic image is a very common technological problem.The main difficulty for this problem is how to minish the color difference between mosaicing images.In this paper,taking two SPOT5 satellite images of Xiamen city,with different seasonal,acquired in different year and with large color difference,as a case,we used several image processing methods,including rescale,raster fill,extraction of feature information and classification etc.to decrease the color difference of two kind ground features:patch one and irregular pieces one.The methods proposed in this paper make possible produce good mosaic images and they are very practical.

Evaluation of colour‐difference formulae for different colour‐difference magnitudes

AbstractMost of the colour‐difference formulae were developed to fit data sets having a limited range of colour‐difference magnitudes. Hence, their performances are uncertain when applying them to a range of colour differences from very small to very large colour differences. This article describes an experiment including three parts according to the colour‐difference magnitudes: large colour difference (LCD), small colour difference (SCD), and threshold colour difference (TCD) corresponding to mean ΔE values of 50.3, 3.5, and 0.6, respectively. Three visual assessment techniques were used: ratio judgement, pair comparison, and threshold for LCD, SCD, and TCD experiments, respectively. Three data sets were used to test six colour‐difference formulae and uniform colour spaces (CIELAB, CIE94, CIEDE2000, CAM02‐SCD, CAM02‐UCS, and CAM02‐LCD). The results showed that all formulae predicted visual results with great accuracy except CIELAB. CIEDE2000 worked effectively for the full range of colour differences, i.e., it performed the best for the TCD and SCD data and reasonably well for the LCD data. The three CIECAM02 based colour spaces gave quite satisfactory performance. © Wiley Periodicals, Inc. Col Res Appl, 2012

Quality of electrophotographic prints on foil substrates

Electrophotographic printing uses many types of substrates, our study focuses on plastic substrates. Six types of regular and self-adhesive foil substrates were chosen to be printed using two electrophotographic presses: Xerox Colour 1000 Press and Canon imagePress C7000VP. A test chart containing tone value scales and a set of samples for profiling was created, spectrophotomety and densitometry was applied to obtain the optical and colorimetric properties of the substrates investigated. Xerox Color 1000 Press produced larger densities and tone value increase on every type of substrate. The largest TVI values and reproducible colour gamut was observed on the smoothest foil in case of both presses. Large colour differences were found between patches of full tone process colors on the different substrates investigated.

Comparing large colour‐difference data sets

AbstractThis study investigated the differences between different large colour‐difference (LCD) data sets (with a mean ΔE value about 10). Six data sets were studied. For each data set, various CIELAB based colour difference models were derived to fit the data. These models were compared to shed light on the difference between the different data sets. It was found that all data sets have very similar characteristics except for the Munsell data. Detailed investigation showed that the discrepancy is mainly due to the balance between the lightness and chromatic differences used previously for the Munsell data set. It was found that one unit of Munsell Value appears to be three times as large colour difference as one unit of Munsell Chroma at least under the experimental conditions for the data sets studied here. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011

Estimating the properties of the chromatic mechanisms mediating the processing of large color differences

Estimating the properties of the chromatic mechanisms mediating the processing of large color differences

Enhanced visualization of oral cavity for early inflamed tissue detection

We describe a color image reconstruction method that enables both direct visualization and direct digital image acquisition from one oral tissue by using various light sources and color compensating filters. In this method, the image of the oral tissue with white light emitting diodes (LEDs) with blue color compensating filter has a larger color difference between the normal and inflamed tissues. The enhanced visualization comes from the white light color mixing between the red normal tissue and bluish white light from the LEDs. With our method, we evaluate the perceived tissue reflectance in each pixel of the image and color reproduction with different illuminated spectra. Our approach to enhancement of visually perceived color difference between normal and inflamed oral tissue involves optimization of illumination and observation conditions by allowing a significant optical contrast of illuminated spectrum to reach the observer's eyes. In comparison with a conventional daylight LED flashlight, a LED with blue filter as the illuminant for oral cavity detection enhances the color difference between normal and inflamed tissues by 32%.

Investigating the effect of texture on the performance of color difference formulae

AbstractTo predict the perceived color differences, the effect of the surface texture on the performance of the color difference formulae was investigated. To this end, knitted polyester fabrics with eight different textures were prepared. The fabrics were dyed by seven dyestuffs in five different depths. The selected pairs from the five samples with different depths in each hue covered small to large color differences. The assessed pair of samples had the same texture and hue, but different depths. A panel of 23 observers assessed the color differences of the pairs by gray scale method. The results showed that for the textile samples with different texture structures, the CIEDE2000 (2:1:1) performed the best followed by CMC (2:1:1), CIE94 (2:1:1), and CIELAB with approximately same performance. In addition, the magnitude of color difference influenced the ability of the formulae to predict the visual assessments and the best performance obtained for medium color differences. The comparison between eight different texture groups indicated that the texture structures of the pairs significantly affected the performance of the color difference formulae. For instance, the PF/3 measures obtained for the eight texture groups by CIEDE2000 (2:1:1) color formula could be varied between 21.98 and 33.37 PF/3 units. © 2009 Wiley Periodicals, Inc., Col Res Appl, 2010.

Spectrophotometric Analysis of Tooth Color Reproduction on Anterior All‐Ceramic Crowns: Part 2: Color Reproduction and Its Transfer from In Vitro to In Vivo

Color reproduction of an anterior tooth requires advanced laboratory techniques, talent, and artistic skills. Color matching in a laboratory requires the successful transfer from in vivo with careful considerations. The purpose of this study was to monitor and verify the color reproduction process for an anterior all-ceramic crown in a laboratory through spectrophotometric measurements. Furthermore, a crown insertion process using composite luting cements was assessed, and the final color match was measured and confirmed. An all-ceramic crown with a zirconia ceramic coping for the maxillary right central incisor was fabricated. There was a significant color difference between the prepared tooth and the die material. The die material selected was the closest match available. The ceramic coping filled with die material indicated a large color difference from the target tooth in both lightness and chromaticity. During the first bake, three different approaches were intentionally used corresponding with three different tooth regions (cervical, body, and incisal). The first bake created the fundamental color of the crown that allowed some color shifts in the enamel layer, which was added later. The color of the completed crown demonstrated an excellent color match, with Delta E 1.27 in the incisal and 1.71 in the body. In the cervical area, color match with Delta E 2.37 was fabricated with the expectation of a color effect from the underlying prepared tooth. The optimal use of composite luting cement adjusted the effect from the underlying prepared tooth color, and the color match fabricated at a laboratory was successfully transferred to the clinical setting. The precise color measurement system leads to an accurate verification of color reproduction and its transfer. CLINICAL SIGNIFICANCE The use of a dedicated dental spectrophotometer during the fabrication of an all-ceramic crown allows the dentist and the laboratory technician to accurately communicate important information to one another about the shade of the tooth preparation, the shade of the contralateral target tooth, and the influence of luting cement on the final restoration, thereby allowing the technician better control over the outcome of their tooth color matching efforts and the final color match of an all-ceramic restoration.

Perceptual prominence of Hering's chromatic primaries

Reported are results of an experiment involving perceptual assessment of very large color differences using samples representing approximate mean Hering opponent generic unique hues (guHs) based on subject selections, intermediate hues (iHs) using Munsell samples intermediate between guHs, and pairings of both guHs and iHs with a neutral gray. Sample pairs were assessed by 28 color normal subjects twice, with a gap of at least 24 hours between assessments. Results were calculated for individual subjects and the entire group. The hypothesis was that perceived chromatic differences of Hering's guHs are larger than those of iHs, and this was found to be statistically valid at the 99% confidence level based on a t-test. In addition, gray as a percept was found to have prominence comparable to that of generic unique hues.

Complexities of cuticular pigmentation in insects

Complexities of cuticular pigmentation in insects