Female Misumenoides formosipes crab spiders, unlike their highly mobile, short-lived male counterparts, are relatively sedentary predators that forage long after the males have died off. Associated with their foraging ability is a phenomenon rare amongst animals: the capacity for a reversible change in body color. This color change ability, exhibited by several species of crab spiders, has historically been interpreted as an adaptation providing enhanced crypsis during movement between hunting substrates (inflorescences). Misumenoides formosipes females were relocated onto matched and mismatched substrates in the field to assess their propensity for color change, the rate at which it occurs, and any impact on foraging success. Yellow females transferred to white inflorescences were the only category that did not remain in their new location. White females changed to yellow over a 9 day period. We found conflicting evidence as to whether or not foraging success was enhanced for females on matched backgrounds. / Department of Biology

This creative project explored and determined the visual characteristics of drawings and paintings of vegetables. The project consisted of a painting and a drawing of the following vegetables: a potato. a pea and pod, a tomato, a carrot, and an onion. The paintings were done in glazes of oil paint and the drawings in colored pencils. Fundamental to this creative investigation was the control of subject matter, composition and color variables. These variables were controlled in order to understand the way in which the media and techniques differentiated the visual appearance of the drawings and paintings.

Colours influence numerous aspects of an animal’s ecology and the adaptive significance of colour variation has been intensively studied in diverse taxonomic groups. This study was motivated by the question: Why do garter snakes vary in colour? To answer this question, I focused on Western Terrestrial Garter Snakes, Thamnophis elegans, which exhibit geographic variation in colouration (dark morph vs. light morph), and two different species of garter snake that occur in the same geographic region but vary in colour –light T. elegans and the Common Garter Snake, T. sirtalis. My work provides an objective quantification and analysis of snake colour and evaluates the influence of colour variation on ecological processes such as thermoregulation, crypsis, and antipredator behaviour. I compared body temperatures (Tbs) with available thermal opportunities, both in wild snakes and in a field experiment, to determine how snakes with contrasting colours differ in thermoregulation and temperature-dependent behaviours. Gravid females of the light and dark colour morphs of T. elegans exhibited comparable thermoregulatory behaviour at high temperatures; however, dark T. elegans maintained elevated Tbs when available temperatures dropped. In the field, dark-coloured snakes were more likely to be moving when first detected when Tbs were high, but this trend was reversed in light T. elegans. I quantified crypsis of snakes, in terms of colour and brightness, by measuring the spectral reflectance of snakes and the surrounding habitat. These data were visually modeled from the perspective of potential snake predators and human researchers. Overall, snakes selected basking sites that maximized crypsis and both colour morphs of T. elegans were equally cryptic. There was evidence suggesting that T. sirtalis was more cryptic than light T. elegans to snake predators. I collected a series of behavioural measurements for snakes pre- and post-capture. Light T. elegans were more likely to be moving when originally detected in the field than dark snakes. Distance to cover and injuries were important factors in explaining the antipredator behaviour of snakes in the field. Snakes became generally faster with increasing Tbs, but differences attributable to colour morph were not straightforward. A higher proportion of T. elegans of both colour morphs exhibited some type of movement when exposed to a simulated predatory attack. Thamnophis sirtalis, on the other hand, hung limp and motionless in the air. The less cryptic light T. elegans had a higher probability of having an injury than T. sirtalis but injury patterns between the equally cryptic light and dark T. elegans differed by sex. The relationships between colour and these various traits were complex, but, taken together, they highlighted how thermal ecology, crypsis, and anti-predator behaviours were related to a snake’s visual appearance. These results therefore provide an ecological underpinning for future genetic studies to identify potential candidate genes that may be responsible for the control of colour pattern in garter snakes. / Graduate / 0329 / 0306 / 0472

No description available.

Introduction Nearly all flat panel video display monitors have luminance and colour variations as the angle of view varies from the monitor’s perpendicular. The new MicrotileTM displays developed by Christie Digital are no exception to this general finding. A review of any book on colour science will show that there is substantial amount of literature on just noticeable colour differences within various colour spaces. Despite the wealth of data on the topic, there is no general consensus across different industries as to which colour space and colour difference equations are appropriate. Several factors like the background colour, object size, texture of the stimulus are different for different studies; these factors make it very difficult to determine precisely the effect of viewing angle on the perception of coloured images on the Microtiles display based on previous research. Hence, the objective of this thesis was to quantify the measured colour shifts of a Microtile display at different viewing angles, in steps of perceptible thresholds and to evaluate the acceptability of distortions at different viewing angles for complex scenes. Methods A preliminary experiment was setup to study the behaviour of Microtile display primaries as a function of viewing angle. The aim was to measure the shift in hue and luminance of the three primaries at different eccentricities (from 0o to 40o). The measured trend was used to simulate Microtile shifts on complex images for the rating task. In the first part of the perceptibility experiment, three reference colours were picked and 12 vectors heading towards the blue-yellow region of the L*a*b* colour space (pertaining to the colour shifts noticed with the Microtile displays). A uniform reference colour was presented in three of the four quadrants on the CRT monitor and one quadrant changed colour in the direction of the sampled vector. An adaptive, four alternate forced choice procedure was employed to determine thresholds for each of the 3 reference colours. The adaptive technique used was a ZEST paradigm. In the second part of the perceptibility experiment, eighteen directions were sampled around each reference colour. The rating task was based on simulating the measured attenuations of the Microtile primaries on complex scenes. Subjects rated the images both in terms of acceptability/unacceptability and as percentage image degradation. The simulation was presented on three static complex images, car, landscape and portrait. A total of 60 subjects participated in the study, 20 subjects for each experiment. All subjects were between the age group of 15 to 35 years of age and underwent battery of colour vision tests before being included in the study. All subjects included had average to superior colour discrimination as categorized using the FM-100 Hue discrimination test. Results Study1: The preliminary study on Microtile display characteristics as a function of viewing angle showed that all the three primaries decreased in luminance with change in viewing angle. The red primary decreased at a faster rate compared to the other two primaries. The trend presents as a decrease in luminance with the hue shifting towards the blue-green region of the CIE1974 L*a*b* space. Study 2: Results from both the first and second parts of the perceptibility experiment showed that the vectors sampled in different directions approximated to ellipsoids in the L*a*b* colour space. This finding was consistent with the colour discrimination literature. Vectors on the equi-luminance plane were significantly longer than the vectors on the non equi-Luminance plane. Results showed that the average perceptibility thresholds in the non equi-luminance direction were lower than 1∆ELab¬¬¬¬. Study 3: Results from the rating experiments showed that irrespective of the complexities in the images, distortions greater than five times thresholds were less than 50% acceptable and were rated to be at least 30% degraded. This corresponds to a viewing angle greater than 10o for a Microtile display. The relationship between the stimulus (ΔE) and subjective Image degradation judgements followed a linear relationship, with the portrait and landscape having similar functions, whereas the car was rated more degraded at lower ΔEs and less degraded at higher ΔEs compared with the other two scenes. Conclusion Perceptibility thresholds for different reference colours showed that the conventionally used calibration precision of 1 ΔELab is a lenient criterion. Perceptibility thresholds are at least 25% less for the Microtile display reference condition. From the results of the rating data a distortion greater than five times thresholds is less than 50% acceptable and appears to be at least 30% degraded for static complex images. However, the image quality judgments appear to be related to scene context, which requires further study.

Red radish anthocyanin extract (RAE) was investigated for coloring brined cherries as an alternative to FD&C Red No. 40. Red radish (Raphanus sativus L.) anthocyanins were extracted from liquid nitrogen powdered epidermal tissue using acetone, partitioned with chloroform, and isolated using C-18 resin. The monomeric anthocyanin content was determined by pH differential to be 154 ± 13 mg/100 g of epidermal tissue (on pelargonidin-glucoside basis). The major pigments were identified as pelargonidin-3-sophoroside-5-glucoside monoacylated with p-coumaric or ferulic acids by HPLC and spectral analyses. Primary and secondary bleached cherries were sweetened to 40° Brix (pH of 3.50), and colored using two concentrations of RAE (600 and 1200 mg/L syrup, designated Cl and C2) and FD&C Red No. 40 (200 ppm). Color was measured for both cherries and syrup. Reflectance measurements (CIE L*, a*, b*), chroma and hue angle, showed that RAE imparted red color to the cherries and syrup extremely close to that of FD&C Red No. 40. RAE C2 gave the primary bleached cherries the closest color characteristics (L*= 18.20, a*= 20.00, b*= 8.47) to FD&C Red No. 40 (L*= 18.00, a*= 24.35, b*= 12.13). RAE Cl gave the secondary bleached cherries the closest color characteristics (L*= 15.27, a*= 16.21, b*= 5.21) to FD&C Red No. 40 (L*= 16.38, a*= 19.91, b*= 8.99). Color and pigment stability of secondary bleached cherries were evaluated during a year of storage in the dark at 25°C. Monomeric anthocyanin degradation followed first-order kinetics and the half-lives were 29 and 33 weeks for syrups colored with RAE Cl and RAE C2, respectively. However, cherry color showed no significant changes in hue, color intensity nor lightness during storage. Color changes of syrup samples over time were dependant on anthocyanin concentration, higher anthocyanin concentration exerted a protective effect on color stability. Haze formation was observed in syrup samples colored with RAE, possibly due to pigment polymerization. Syrup samples colored with RAE and FD&C Red No. 40 were also exposed to light for a year at 25°C. Light had a small but significant effect on L*, a*, and monomeric anthocyanin content. From color and pigment stability data and visual observations we concluded that RAE was effective in coloring secondary bleached cherries with results very similar to those of FD&C Red No. 40 for 6 months of storage. / Graduation date: 1995

Single image matting refers to the problem of accurately estimating the foreground object given only one input image. It is a fundamental technique in many image editing applications and has been extensively studied in the literature. Various matting techniques and systems have been proposed and impressive advances have been achieved in efficiently extracting high quality mattes. However, existing matting methods usually perform well for relatively uniform and smooth images only but generate noisy alpha mattes for complex images. The main motivation of this thesis is to develop a new matting approach that can handle complex images. We examine the color sampling and alpha propagation techniques in detail, which are two popular techniques employed by many state-of-the-art matting methods, to understand the reasons why the performance of these methods degrade significantly for complex images. The main contribution of this thesis is the development of two novel matting algorithms that can handle images with complex texture patterns. The first proposed matting method is aimed at complex images with homogeneous texture pattern background. A novel texture synthesis scheme is developed to utilize the known texture information to infer the texture information in the unknown region and thus alleviate the problems introduced by textured background. The second proposed matting algorithm is for complex images with heterogeneous texture patterns. A new foreground and background pixels identification algorithm is used to identify the pure foreground and background pixels in the unknown region and thus effectively handle the challenges of large color variation introduced by complex images. Our experimental results, both qualitative and quantitative, show that the proposed matting methods can effectively handle images with complex background and generate cleaner alpha mattes than existing matting methods.

Graduation date: 1951

Graduation date: 1984

Graduation date: 1998