The human visual system gathers information about three-dimensional object shape from a wide range of sources. How effectively we can use these sources, and how they are combined to form a consistent and accurate percept of the 3D world is the focus of much research. In complex scenes inter-reflections of light between surfaces (mutual illumination) can occur, creating chromatic illumination gradients. These gradients provide a source of information about 3D object shape, but little research has been conducted into the capabilities of the visual system to use such information. The experiments described here were conducted with the aim of understanding the influence of chromatic gradients from mutual illumination on 3D shape perception. Psychophysical experiments are described that were designed to investigate: If the human visual system takes account of mutual illumination when estimating 3D object shape, and how this might occur; How colour shading cues are integrated with other shape cues; The relative influence on 3D shape perception of achromatic (luminance) shading and chromatic shading from mutual illumination. In addition, one chapter explores a selection of mathematical models of cue integration and their applicability in this case. The results of the experiments suggest that the human visual system is able to quickly assess and take account of colour mutual illuminations when estimating 3D object shape, and use chromatic gradients as an independent and effective cue. Finally, mathematical modelling reveals that the chromatic gradient cue is likely integrated with other shape cues in a way that is close to statistically optimal.

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The human visual system gathers information about three-dimensional object shape from a wide range of sources. How effectively we can use these sources, and how they are combined to form a consistent and accurate percept of the 3D world is the focus of much research. In complex scenes inter-reflections of light between surfaces (mutual illumination) can occur, creating chromatic illumination gradients. These gradients provide a source of information about 3D object shape, but little research has been conducted into the capabilities of the visual system to use such information. The experiments described here were conducted with the aim of understanding the influence of chromatic gradients from mutual illumination on 3D shape perception. Psychophysical experiments are described that were designed to investigate: If the human visual system takes account of mutual illumination when estimating 3D object shape, and how this might occur; How colour shading cues are integrated with other shape cues; The relative influence on 3D shape perception of achromatic (luminance) shading and chromatic shading from mutual illumination. In addition, one chapter explores a selection of mathematical models of cue integration and their applicability in this case. The results of the experiments suggest that the human visual system is able to quickly assess and take account of colour mutual illuminations when estimating 3D object shape, and use chromatic gradients as an independent and effective cue. Finally, mathematical modelling reveals that the chromatic gradient cue is likely integrated with other shape cues in a way that is close to statistically optimal.

<p>The purpose of this master’s thesis was to study the possibility to use computer vision methods to detect and classify objects in the front passenger seat in a car. This work presents different approaches to solve this problem and evaluates the usefulness of each technique. The classification information should later be used to modulate the speed and the force of the airbag, to be able to provide each occupant with optimal protection and safety.</p><p>This work shows that computer vision has a great potential in order to provide data, which may be used to perform reliable occupant classification. Future choice of method to use depends on many factors, for example costs and requirements on the system from laws and car manufacturers. Further, evaluation and tests of the methods in this thesis, other methods, the ABE approach and post-processing of the results should also be made before a reliable classification algorithm may be written.</p>

<p>Virtually all diurnal birds have tetrachomatic vision based on four different colour receptors. As a result, birds are potentially able to perceive their environment in twice as many colours as humans and four times as many colours compared to most other mammals, which are dichromatic. In addition to the spectrum visible to humans, birds are able to detect ultraviolet (UV) light. Signals with a UV component have been shown to be important to birds both in foraging and colour signalling. Because of the superior colour discrimination of the avian eye, UV sensitivity, but especially owing to its tetrachromacy, we cannot know what birds look like to those that matter, i.e. other birds.</p><p>In my thesis I describe a new molecular method with which it is possible to identify the vision system of birds only using a small amount of DNA, without the need to keep or sacrifice the animal. It thereby facilitates large screenings, including rare and endangered species. The method has been used to increase the number of species with identified vision system type from 19 to 66. I show that raptors and songbirds have different vision systems, giving songbirds the possibility of a secret channel for colour signalling, and that male songbirds in coniferous forest take advantage of this to be significantly more cryptic to raptors than to females songbirds. I show that gulls have gained a vision system enabling them to detect the UV signals of fish when the fish swim close to the surface.</p><p>Even though we tend to be rather self-satisfied with the quality of our colour vision, we are colour-blind when compared to birds. My work shows that human colour vision is inadequate for judging animal coloration, and that there is much more going on in bird colour signalling than meets our eye.</p>

Virtually all diurnal birds have tetrachomatic vision based on four different colour receptors. As a result, birds are potentially able to perceive their environment in twice as many colours as humans and four times as many colours compared to most other mammals, which are dichromatic. In addition to the spectrum visible to humans, birds are able to detect ultraviolet (UV) light. Signals with a UV component have been shown to be important to birds both in foraging and colour signalling. Because of the superior colour discrimination of the avian eye, UV sensitivity, but especially owing to its tetrachromacy, we cannot know what birds look like to those that matter, i.e. other birds. In my thesis I describe a new molecular method with which it is possible to identify the vision system of birds only using a small amount of DNA, without the need to keep or sacrifice the animal. It thereby facilitates large screenings, including rare and endangered species. The method has been used to increase the number of species with identified vision system type from 19 to 66. I show that raptors and songbirds have different vision systems, giving songbirds the possibility of a secret channel for colour signalling, and that male songbirds in coniferous forest take advantage of this to be significantly more cryptic to raptors than to females songbirds. I show that gulls have gained a vision system enabling them to detect the UV signals of fish when the fish swim close to the surface. Even though we tend to be rather self-satisfied with the quality of our colour vision, we are colour-blind when compared to birds. My work shows that human colour vision is inadequate for judging animal coloration, and that there is much more going on in bird colour signalling than meets our eye.

The purpose of this master’s thesis was to study the possibility to use computer vision methods to detect and classify objects in the front passenger seat in a car. This work presents different approaches to solve this problem and evaluates the usefulness of each technique. The classification information should later be used to modulate the speed and the force of the airbag, to be able to provide each occupant with optimal protection and safety. This work shows that computer vision has a great potential in order to provide data, which may be used to perform reliable occupant classification. Future choice of method to use depends on many factors, for example costs and requirements on the system from laws and car manufacturers. Further, evaluation and tests of the methods in this thesis, other methods, the ABE approach and post-processing of the results should also be made before a reliable classification algorithm may be written.

The digital world is acquiring more space in today’s society. With this being said, it is important to keep the web content interpretable for everyone, despite any kind of disability. This study focuses on colour vision deficiency and how to implement a real-time colour correction instantly in the web browser, without any additional assistive technologies needed. Two almost identical webpages have been developed for this project, with the difference being that one is with a colour correction function and one without, who then are measured in page-loading time to see if there is any greater loss of performance when executing the colour conversion.

There has been limited research done to determine the impact of the use of colour on communication displays in the facilitation of graphic symbol location within an overlay. As many Augmentative and Alternative Communication systems are pictorial in nature, it is of importance that interventionists are aware of the potential impact that colour can have on the accuracy and rate of symbol location. The present study is based on a study by Wilkinson, Carlin and Jagaroo (2006) and used the same testing material (colour conditions) whilst modifying the type of exposure to these colour conditions. This study investigated the effect of sequential exposure of colour conditions on the rate and accuracy of graphic symbol location. The study used a comparative, non-experimental group design using sixty participants who conformed to specific selection criteria. Each participant was exposed to three colour conditions that were placed in a specific sequential order. The participants were required to match a target, graphic symbol within an array of symbols in the differing colour conditions. Two different types of graphic symbols were used meaningful (Type A) and arbitrary (Type B). Two different colour sets were also used with the colour conditions varying in each set. Set 1 were the sequentially ordered colour conditions of same colour, mixed colour and unique colour symbols (difficult to easy) while Set 2 were the sequentially ordered colour conditions of unique colour, mixed colour and same colour symbols (easy to difficult). The major findings of the study were as follows. In terms of rate, there was a significant interaction noted between the two symbol types and their sequential ordering. The time taken (rate) for the location of the nonreferential forms was slower than that taken for the meaningful symbols. The reasoning behind this result could be that the non-referential forms were not as familiar to the participants as the meaningful symbols were. Thus, the rate recording of the meaningful symbols and the non-referential forms described in the three colour conditions was different and could be noted in the results. In terms of accuracy, a significant impact was noted between the two symbol types when the first manner of sequential ordering was used, however, there were no significant differences noted when the second manner of sequential ordering was used. This implies greater accuracy was recorded when the second manner of sequential ordering was used as this ordering appeared to be “visually easier” for the location of symbols. / Dissertation (MA)--University of Pretoria, 2009. / Centre for Augmentative and Alternative Communication / unrestricted

With increasing demand placed on online accessibility, a tool that enables developers to more easily build accessible websites for colour vision deficient (CVD) internet users becomes a crucial consideration. An extension was developed for the web browser, Google Chrome, and issues for CVD internet users were identified. The identification was based on the luminance and colour contrast between different objects next to each other on a web page, such as fonts and their background. The extension calculated how a CVD internet user would experience the colours and then checked the contrast between them. The extension's calculations and reliability was assessed through a evaluation with CVD internet users and the results suggested that it would be possible to reliably detect issues related to CVD internet users with a algorithm implemented in a Chrome extension. / Med ökande krav på tillgänglighet på internet så ökar behovet av ett verktyg som underlättar för utvecklare att bygga hemsidor för personer med defekt färgseende. Ett tilläggsprogram utvecklades för webbläsaren Google Chrome, och problem för personer med defekt färgseende identifierades. Identifikationen baserades på luminanskontrast och färgkontrast mellan olika närliggande objekt på en hemsida, så som fonter och deras bakgrund. Tilläggsprogrammet beräknade hur en person med defekt färgseende upplever färgerna på hemsidan och kontrollerar kontrasten mellan dem. Tilläggsprogrammets tillförlitlighet bedömdes med hjälp av en utvärdering genomförd med personer med defekt färgseende. Utvärderingen indikerade att det är möjligt att tillförlitligt identifiera problem relaterade till personer med defekt färgseende med hjälp av en algoritm implementerad i ett Chrome tilläggsprogram.