Effects of texture on color difference evaluation of surface color

The parametric effects of texture on supratheshold color tolerance thresholds were investigated in two psychophysical experiments using simulated textures presented on a CRT. Textured images were created from scanned photographs of physical texture samples with semi-random textured pattern. Differences in appearance were created by varying the illumination geometry during the image capture stage. Two conditions were simulated: diffuse illumination of a standard light booth and directional lighting which accentuates texture relief. In the first experiment observers matched average perceived lightness of grayscale textured images by adjusting the lightness of a uniform gray field. Images varied in their average L*. The results showed that, on average, there was no statistically significant difference between the observer match and the average L of the image. The only exception was found for darker images of coarse texture. In the second experiment, an array of color images was created from three texture patterns: one simulating diffuse lighting conditions and two simulating directional illumination. The CTELAB coordinates of the images were centered around the five CEE color centers recommended for color tolerance research. Color differences were varied in the lightness, chroma, and hue dimensions. Color tolerance thresholds were measured in each dimension for each texture type and uniform patches. An adaptive psychophysical technique, QUEST, was utilized to determine color tolerances in a greater than/less than task using test pairs in comparison to a fixed anchor pair of 1 unit AE*94. The results indicated that the presence of texture increases tolerance thresholds for hue irrespective of the texture pattern. The chroma dimension remained unaffected. Less conclusive results were found for lightness dimension with a strong trend toward increased tolerance thresholds for textured stimuli. When the different textures were compared, it was found that the L* thresholds were significantly higher for the images simulating directional lighting compared to the images of diffusely illuminated surface. No differences in tolerances for chroma and hue were found in that case

Uniform color spaces based on CIECAM02 and IPT color difference equations

Color difference equations based on the CIECAM02 color appearance model and IPT color space have been developed to fit experimental data. There is no color space in which these color difference equations are Euclidean, e.g. describe distances along a straight line. In this thesis, Euclidean color spaces have been derived for the CIECAM02 and IPT color difference equations, respectively, so that the color difference can be calculated as a simple color distance. Firstly, the Euclidean line element was established, from which terms were derived for the new coordinates of lightness, chroma, and hue angle. Then the spaces were analyzed using performance factors and statistics to test how well they fit various data. The results show that the CIECAM02 Euclidean color space has performance factors similar to the optimized CIECAM02 color difference equation. To statistical significance, the CIECAM02 Euclidean color space had superior fit to the data when compared to the CIECAM02 color difference equation. Conversely, the IPT Euclidean color space performed poorer than the optimized IPT color difference equation. The main reason is that the line element for the lightness vector dimension could not be directly calculated so an approximation was used. To resolve this problem, a new IPT color difference equation should be designed such that line elements can be established directly

Preferences and tolerances in color image reproduction

Observer preferences in the color reproduction of pictorial images have been a topic of debate for many years. Through a series of three psychophysical experiments we are trying to better understand the differences and trends in observer preferences for pictorial images, determine if cultural biases on preference exist, and finally generate a set of preferred color reproduced images for future experimentation and evaluation. The first experiment was a survey of observers rating the importance of commonly used image characteristics terms in correlation to color image quality. The data collected demonstrated that observer preferences remain relatively constant while judging color attributes between different media and for various image content. Experiment I also aided in the decision to utilize five dimensions of manipulation to generate preferred color reproductions, for Experiments II and in. The dimensions were, lightness (gamma adjustment to L*), contrast (sigmoid adjustment to L*), chroma (multiplicative factor on Cab* at a given hab), hue rotation, and color balance (additive adjustments to a* and b*). The second experiment was a rank order of image preference conducted at several research facilities around the world. The results yielded that statistical difference between peak preferences of image quality between cultures may exist but that the cultural difference is most likely not of practical significance for most applications. Furthermore, the shape of the preference curves across cultures is very similar so any cultural bias present is small. The final experiment was an adjustment experiment, in which observers were asked to generate the most preferred image possible. The observer variability (inter-observers) and repeatability (intra-observer) in generating preferred images were analyzed. The analysis of Experiment HI yielded that the intra-observer repeatability of an observer is about half of the variation between observers. Furthermore the analysis demonstrated that preferences on images with faces have a much tighter range of preference in comparison to images without faces. Finally, a cross analysis of Experiment II and HI was completed by the generation of preferred image sets from the results of the two experiments. The resultant images proved to be a good visualization of the range of variability in making preferred images from the color dimensions provided, and also visually demonstrated that the two techniques, (making one color adjustment at a time verses compounding color adjustments) of generating preferred images result in similar solutions

Visual determination of hue suprathreshold tolerances

A visual experiment was performed to generate suprathreshold tolerances sampling the direction of CIELAB hue, thereby extending the RIT-Dupont dataset. Thirty nine color centers including three complete hue circles at different lightness or chroma levels and three CIE recommended colors (red, green, blue) were evaluated for hue discrimination. Forty five observers participated in the pass/fail experiments. A total of 32,226 visual observations were made. The statistical method, logit analysis with 3-dimensional normit function, was used to determine the hue discrimination suprathreshold for each color center. The results indicated that the hue discrimination suprathresholds of observers varied with hue angle. The suprathreshold also increased with the chroma position of a given color center. The results were compared with current color-difference formulae, CMC, BFD and CIE94. A mathematical equation was derived from the present dataset

Effect of Toothbrushing on Surface Roughness and Shade of Extrinsically Stained Pressable Ceramic Restorations

The purpose of this study was to investigate the effects of toothbrushing on surface roughness and shade change of extrinsically stained pressable ceramic restorations. Materials and Methods: Two materials, IPS Empress Esthetic and IPS e.max Press, were studied. For each material, 24 disc-shaped specimens, 10mm (diameter) x 3mm (height) were fabricated. Three different methods (n=8) of applying extrinsic stain was performed on each material: Glazed (G): glazed only (control); Stain then Glaze (SG): stained and fired, then glazed and fired. Stained and Glazed (T): glazed and stained together. Samples where brushed using a multi-station brushing machine. Each specimen was brushed for 72, 144, 216 and 288 h (equivalent to 3, 6, 9 and 12 years of simulated toothbrushing twice a day for 2 min) with a force of 200 g at a rate of 90 strokes/min using a soft, straight Oral-B #35 toothbrush and a 1:1 toothpaste and distilled water slurry. Roughness and color were evaluated at baseline and every 3 year equivalent up to 12 years of simulated toothbrushing. Results: No significant difference was found for surface roughness or shade change over time irrespective of technique for the IPS Empress Esthetic (EE) groups. IPS e.max Press (EP) demonstrated an increase roughness over time (P\u3c.01) irrespective of technique (P=.709). Shade change over time depended on the technique (P=.005). The stain then glaze (EP-SG) behaved better over time (P=.039). Conclusions: Within the limitations of this study it can be concluded that no clinically significant shade change for both IPS Empress Esthetic and IPS e.max Press should be expected after 12 years of toothbrushing. IPS Empress Esthetic stains and glaze were more resistant to toothbrush abrasion

Estimating Color-Concept Associations from Image Statistics

To interpret the meanings of colors in visualizations of categorical information, people must determine how distinct colors correspond to different concepts. This process is easier when assignments between colors and concepts in visualizations match people's expectations, making color palettes semantically interpretable. Efforts have been underway to optimize color palette design for semantic interpretablity, but this requires having good estimates of human color-concept associations. Obtaining these data from humans is costly, which motivates the need for automated methods. We developed and evaluated a new method for automatically estimating color-concept associations in a way that strongly correlates with human ratings. Building on prior studies using Google Images, our approach operates directly on Google Image search results without the need for humans in the loop. Specifically, we evaluated several methods for extracting raw pixel content of the images in order to best estimate color-concept associations obtained from human ratings. The most effective method extracted colors using a combination of cylindrical sectors and color categories in color space. We demonstrate that our approach can accurately estimate average human color-concept associations for different fruits using only a small set of images. The approach also generalizes moderately well to more complicated recycling-related concepts of objects that can appear in any color.Comment: IEEE VIS InfoVis 2019 ACM 2012 CSS: 1) Human-centered computing, Human computer interaction (HCI), Empirical studies in HCI 2) Human-centered computing, Human computer interaction (HCI), HCI design and evaluation methods, Laboratory experiments 3) Human-centered computing, Visualization, Empirical studies in visualizatio

A Colorimetric analysis of color variation due to changes in simulated ink trapping

The purpose of this study was to address, through colorimetric analysis, color variation as it relates to the efficiency of trapping. A developing awareness of colorimetric analysis in the graphic arts, as well as the realization of some of the limitations of densitometry when applied to color analysis provided impetus for such a study

A Study of High-Chroma Inks for Expanding CMYK Color Gamut

The number of possible reproducible colors in a printing method is called the color gamut. The need to satisfy the growing quality demands and produce color match has given rise to the use of expanded color gamuts. There are many ways to achieve an expanded color gamut, including printing with Cyan, Magenta, Yellow, Black (CMYK) plus additional inks, printing with higher ink film thickness (IFT), and printing with high-chroma inks. The purpose of this research is to study the relationship between color gamut volume, metric chroma (C*), IFT, and solid ink density (SID) for regular and high-chroma inks in offset printing process. This is done by performing ink drawdowns to understand the behavior of high-chroma and regular inks in order to determine IFT and corresponding ink saturation densities using the Tollenaar and Ernst equation. Subsequently, the research compares color gamut volume between regular and high-chroma inks using Presstek 52DI offset printing process. The measurement is carried out with i1 Pro 2 spectrophotometer and X-Rite i1 Isis2

Värit kiertotaloudessa

This thesis presents a research that explores the possibilities of colours in the circular economy of textiles. Waste fabrics of various origins serve as a starting point: their colours’ potential for circularity is studied and possible areas of application are evaluated. The research is conducted as part of the EU-funded, multi-disciplinary project Trash2Cash, and uses the recently developed cellulose dissolution and regeneration process Ioncell-F as a key method to demonstrate colour circulation from discarded textile to fibres of the next generation. Methods used in this research include a literature overview that addresses key issues of sustainability in modern cellulosic material production and textile dyeing. The literature overview also offers theoretical background knowledge of the circular economy and the role of colour in various areas of fashion. Dyeing and fibre remanufacturing practices that could be applied to regenerated dyed textiles are charted through interviews and personal communication with professionals. Prototypes demonstrate various regeneration behaviours of textile dyes. These behaviours are examined and some of them are placed into a speculative context. The result is a theoretical dye concept, which is intended to be applied to both pre-consumer and post-consumer textiles. The concept provides guidelines for the minimal use of virgin materials and dyestuff and contributes to the systemic regenerative principles of circular economy. This study could help to define the parameters of a circular economy product more accurately in terms of its efficiency in remanufacturing. Dyed fabrics could be seen not only as raw material for the next generation of fibres, but as their colorant as well. Future colour designers could get creative with mixing and coordinating colours: creating colour stories from existing discarded textiles might be an interesting and challenging new job description for a professional working closely with colour design or colour forecasting. The research at hand could thus cater to the constant demand for new colours without compromising principles of sustainability.Tässä opinnäytetyössä tutkitaan värejä tekstiilien kiertotaloudessa. Työn lähtökohtana ovat värjätyt kankaat, tekstiilivärien kierrätys materiaalikierrätyksen yhteydessä sekä sen mahdolliset sovellusalueet. Tutkimus on toteutettu osana EU-rahoitteista, monialaista hanketta Trash2Cash. Tutkimuksen testiosuudessa käytetään hiljattain kehitettyä selluloosan liuotukseen ja regenerointiin perustuvaa Ioncell-F -prosessia havainnollistamaan värien kiertoa hävitettävästä tekstiilistä uuden sukupolven kuituun. Tutkimusmenetelmiin kuuluu kirjallisuuskatsaus, jossa käsitellään mm. selluloosamateriaalien tuotantoon sekä tekstiilivärjäämiseen liittyvät ympäristöongelmat. Kirjallisuudesta haetaan myös tietoa kiertotaloudesta ja värien roolista muodin eri aloilla. Tekstiilivärjäämiseen ja kuitujen talteenottoon liittyviä käytänteitä pyritään selvittämään haastatteluilla ja keskusteluilla alan ammattilaisten kanssa.Testiosuudessa valmistetaan prototyyppejä, jotka havainnollistavat tekstiilivärien käyttäytymistä kemiallisessa uusiovalmistuksessa. Prototyyppien käsittelyssä tapahtuvat väri-ilmiöt dokumentoidaan ja niistä muutama sijoitetaan spekulatiiviseen kontekstiin. Työssä esitetään värikonsepti, joka perustuu edellä mainituin keinoin kerättyyn tietoon ja on suunniteltu sovellettavaksi sekä käyttämättömiin jätekankaisiin että kulutuskäytössä olleeseen tekstiilijätteeseen. Konsepti ohjaa neitseellisten raaka-aineiden ja väriaineiden käytön minimointiin, sekä keskittyy kiertotalousajattelulle ominaiseen uusiutuvuuteen. Tämä tutkimus voi määrittää tarkemmin kiertotaloustuotteen parametrit. Värjätyt kankaat voivat toimia raaka-aineen lisäksi myös väriaineena seuraavan sukupolven kuiduille. Tutkimuksessa kehitetyt värikonseptiehdotukset pyrkivät antamaan ohjeita hävitettävien tekstiilimateriaalien uudelleenvalmistukselle ja värisuunnittelijat voivat sen yhteydessä soveltaa luovuuttaan uusien värien sekoittamisessa sekä värimaailmojen ideoimisessa. Konsepti enteilee mielenkiintoista ja haastavaa uutta työnkuvaa asiantuntijoille, jotka työskentelevät värien tai väriennustamisen parissa. Uusia värejä kaivataan jatkuvasti, ja tämä tutkimus voisi tarjota lähestymistavan niiden tuottamiseen tekstiileissä kestävän kehityksen periaatteet huomioiden

A Colorimetric investigation of soft proofing

The color proof has become one of the most important tools for quality control in the printing industry today3. Customers, publishers, separators, and printers depend upon its accuracy for indicating the quality of separations. The color proof is the most practical method for communicating how the color should appear and is easy to understand and use for comparison. The analog color proof is compared to the original to determine if the desired result has been achieved. The proof is sent to the customer to indicate how the image will appear when printed. If this proof is accepted, it is sent to the press room to indicate what is expected in the final reproduction. The color proof visually simulates how a set of films will print on the final production press with the production inks and stock. However, all too often, what is seen on the proof is not what the customer receives