Eye tracking observers during color image evaluation tasks

This thesis investigated eye movement behavior of subjects during image-quality evaluation and chromatic adaptation tasks. Specifically, the objectives focused on learning where people center their attention during color preference judgments, examining the differences between paired comparison, rank order, and graphical rating tasks, and determining what strategies are adopted when selecting or adjusting achromatic regions on a soft-copy display. In judging the most preferred image, measures of fixation duration showed that observers spend about 4 seconds per image in the rank order task, 1.8 seconds per image in the paired comparison task, and 3.5 seconds per image in the graphical rating task. Spatial distributions of fixations across the three tasks were highly correlated in four of the five images. Peak areas of attention gravitated toward faces and semantic features. Introspective report was not always consistent with where people foveated, implying broader regions of importance than eye movement plots. Psychophysical results across these tasks generated similar, but not identical, scale values for three of the five images. The differences in scales are likely related to statistical treatment and image confusability, rather than eye movement behavior. In adjusting patches to appear achromatic, about 95% of the total adjustment time was spent fixating only on the patch. This result shows that even when participants are free to move their eyes in this kind of task, central adjustment patches can discourage normal image viewing behavior. When subjects did look around (less than 5% of the time), they did so early during the trial. Foveations were consistently directed toward semantic features, not shadows or achromatic surfaces. This result shows that viewers do not seek out near-neutral objects to ensure that their patch adjustments appear achromatic in the context of the scene. They also do not scan the image in order to adapt to a gray world average. As demonstrated in other studies, the mean chromaticity of the image influenced observers\u27 patch adjustments. Adaptation to the D93 white point was about 65% complete from D65. This result agrees reasonably with the time course of adaptation occurring over a 20 to 30 second exposure to the adapting illuminant. In selecting the most achromatic regions in the image, viewers spent 60% of the time scanning the scene. Unlike the achromatic patch adjustment task, foveations were consistently directed toward achromatic regions and near-neutral objects as would be expected. Eye movement records show behavior similar to what is expected from a visual search task

Quantification of impacts of colour on affective quality of images

Most consumer images serve emotional functions as well as informational ones. The impression of an image can be affected not only by physical properties e. g. size, colour and media but also by the context of images, aesthetic properties and social/personal backgrounds of observers. However in traditional frameworks in image quality studies, the impacts of colour-appearance attributes on image quality have focused on maximising the informational functions of images, considering an image as a reproduced copy of a real scene. Thus, a new approach was adopted in this study in an attempt to investigate the emotional aspect of an image. The goal of this research is to study the impact of colour-appearance attributes of an image on emotional responses, and to develop quantitative models for predicting emotional response considering the context of the image. To achieve this goal, three sets of psychophysical and physiological experiments have been conducted. First, the relationship between colour-appearance attributes and overall affective response to images was investigated for four different types of image contents. It was found that image colourfulness and lightness contrast had a consistent influence on these relationships for all types of images. The relationships between emotional responses of image pleasantness and excitement were significantly different between positive images and negative images. Accordingly, quantitative models of image pleasantness and excitement were developed as a function of image colourfulness and contrast separately for the two groups of images. Finally, models of image pleasantness and excitement for positive and negative images were developed as a linear equation based on models developed for each colour attribute. The relationships between colour-appearance attributes and responses on colour-emotion scales, active-passive, heavy-light and warm-cool, were also studied for four different types of image content. Quantitative models of the three colour-emotion scales were developed as a function of colour attributes of images such as lightness, colourfulness and lightness contrast. As an application of using the colour-emotion model developed for images, the relationships between colouremotion scales and image emotion were investigated and quantitative models of image pleasantness and excitement were developed as functions of three colouremotion scales for two groups of images: positive and negative. The model performance based on the colour-emotion scales was compared with the performance of models based on the colour attributes. As a result, the latter model performed better than former. The impact of image content and colour attributes of an image on emotional responses to images was investigated by measuring physiological responses to images which were compared with the psychophysical responses. It was found that the activities in skin conductance and heart rate showed significantly greater responses for the images with personal meanings and significances. For the effect of colour attributes in images, it was found that more chromatic images generated higher activity in skin conductance responses. It was also found that lower contrast images generated higher activity in corrugator EMG responsesEThOS - Electronic Theses Online ServiceGBUnited Kingdo