Lau, Sin Heng. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 17). / Abstracts in English and Chinese.

圖像相似性度量準則是一個傳統的研究領域。大量經典的圖像處理技術被用來為各種類型的圖像設計相似性度量準則，這些圖像包括了線條圖，灰度圖，彩圖以及高動態範圍圖像。儘管已有的度量準則在指定的條件下可以實現優良的圖像相似度比較，這些度量準則極少系統地考慮或檢驗自身與人類視覺感知之間的一致性。而與人類知覺的一致性是由大量實際應用提出的共同需求。隨著三維立體設備的廣泛應用，圖像的相似性已經不只是傳統的可視差別，更包括了人眼利用三維立體設備同時觀看兩張不同的圖片時的視覺可接受度。 / 非嚴謹對準形狀相似性度量準則（AISS）可以比較兩幅具有固定尺寸的線條圖的形狀相似度。對於該度量準則，兩幅待比較圖像的形狀不要求完全對齊，同時，又會考慮到圖像的形變，例如位置，方向和縮放上的變化。 / 雙目觀看舒適度預測器（BVCP）是另一個度量準則。當人的雙眼同時觀看兩幅不同的圖像時，該準則可用以預測視覺的舒適度。根據著名的双眼單视理論，人的視覺可以將兩幅具有細節、對比度以及亮度差別的圖像合成一幅圖像，只要這些差別在限定的程度之內。在計算機圖形學領域，BVCP 首次嘗試去預測雙目的圖像差別會否引起觀看的不舒適。 / 在本論文中，實用的應用程序也被提出用以衡量AISS 和BVCP。AISS 被用在了一個名為“基於結構的ASCII 藝術的應用程序中，該應用程序可以利用ASCII 字符的形狀近似地表現參考圖像的線條結構信息。而BVCP 則被用在一個創新地應用框架中，該框架可以從單幅高動態範圍圖像中生成一組（兩幅）低動態範圍圖像。當這一組低動態範圍圖像組被人的雙眼同時觀看時，可以比傳統的單幅低動態範圍圖像保留更多的人類可感知視覺信息。可信的結果和使用者研究也用來證明SSIM 和BVCP 的有效性以及與人類知覺的一致性。 / Image similarity metric is a traditional research field. Classical image processing techniques are used to design similarity metrics for all kinds of images, such as line drawings, gray or color image and even high-dynamic range (HDR) images. While existing metrics perform well for the tasks of comparing images in specified situations, few of them have systematically considered or examined the consistency with human perception required by practical applications. With the blooming of stereo devices, the similarity to be measured is not only the traditional visual difference between two images, but also the visual acceptance of two images when they are viewed simultaneously with 3D devices. This thesis presents two image similarity metrics motivated by perceptual principles, also with applications to demonstrate their novelty and practical values. / Alignment-Insensitive Shape Similarity Metric (AISS) measures shape similarity of line drawings. This metric can tolerate misalignment between two shapes and, simultaneously, accounts for the differences in transformation such as, position, orientation and scaling. / Binocular Viewing Comfort Predictor (BVCP) is another metric proposed to measure visual discomfort when human's two eyes view two different images simultaneously. According to a human vision phenomenon - binocular single vision, human vision is able tofuse two images with differences in detail, contrast and luminance, up to a certain limit. BVCP makes a first attempt in computer graphics to predict such visual comfort limit. / Applications are also proposed to evaluate AISS and BVCP. AISS is utilized in an application of Structure-based ASCII Art, which approximates line structure of the reference image content with the shapes of ASCII characters. BVCP is utilized in a novel framework - Binocular Tone Mapping which generates a binocular low-dynamic range (LDR) image pair from one HDR image. Such binocular LDR pair can be viewed with stereo devices and can preserve more human-perceivable visual content than traditional one single LDR image. Convincing results and user studies are also shown to demonstrate that both AISS and BVCP are consistent with human perception and effective in practical usage. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Linling. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 122-132). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Acknowledgement --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Alignment-Insensitive Shape Similarity Metric --- p.8 / Chapter 2.1 --- Related Work --- p.10 / Chapter 2.2 --- Design of AISS --- p.13 / Chapter 2.2.1 --- Misalignment Tolerance --- p.14 / Chapter 2.2.2 --- Transformation Awareness --- p.16 / Chapter 2.2.3 --- Parameter Setting --- p.17 / Chapter 2.3 --- Results and Discussion --- p.18 / Chapter 2.4 --- Discussion --- p.20 / Chapter 3 --- Application for AISS: Structure-based ASCII Art --- p.21 / Chapter 3.1 --- Overview --- p.24 / Chapter 3.2 --- Optimization --- p.28 / Chapter 3.3 --- User Study and Discussion --- p.35 / Chapter 3.3.1 --- Metrics Comparison --- p.35 / Chapter 3.3.2 --- Comparison to Existing Work --- p.38 / Chapter 3.3.3 --- User Study --- p.40 / Chapter 3.4 --- Summary --- p.44 / Chapter 4 --- Binocular Viewing Comfort Predictor --- p.48 / Chapter 4.1 --- Background --- p.51 / Chapter 4.2 --- Design of BVCP --- p.54 / Chapter 4.2.1 --- Fusional Area --- p.55 / Chapter 4.2.2 --- Contour Fusion --- p.58 / Chapter 4.2.3 --- Contour and Regional Contrasts --- p.68 / Chapter 4.2.4 --- Failure of Rivalry --- p.70 / Chapter 4.2.5 --- The Overall Fusion Predictor --- p.74 / Chapter 4.3 --- User Study --- p.77 / Chapter 4.4 --- Discussion and Limitations --- p.84 / Chapter 5 --- Application for BVCP: Binocular Tone Mapping --- p.86 / Chapter 5.1 --- Framework --- p.90 / Chapter 5.1.1 --- Overview --- p.90 / Chapter 5.1.2 --- Optimization --- p.93 / Chapter 5.2 --- Results and Discussion --- p.96 / Chapter 5.2.1 --- Results --- p.96 / Chapter 5.2.2 --- User Study --- p.103 / Chapter 5.2.3 --- Incorporating Stereopsis --- p.106 / Chapter 5.2.4 --- Limitations --- p.109 / Chapter 5.3 --- Summary --- p.112 / Chapter 6 --- Conclusion --- p.113 / Chapter A --- User Study for ASCII art --- p.117 / Bibliography --- p.122

No description available.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 225-237. / by William Eric Leifur Grimson. / Ph.D.

Despite their small brains, insects are capable of incredible navigational feats. Even Drosophila melanogaster (the common fruit fly) uses visual cues to remember locations in the environment. Investigating sophisticated navigation behaviors, like visual place learning, in a genetic model organism enables targeted studies of the neural circuits that give rise to these behaviors. Recent work has shown that the ellipsoid body, a midline structure deep within the fly brain, is critical for certain navigation behaviors. However, nearly all aspects of visual place learning remain mysterious. What visual features are used to encode place? What is the site of learning? How do the learned actions integrate with the core navigation circuits? To begin to address these questions I have established an experimental platform where I can measure neural activity using a genetically encoded calcium indicator in head-fixed behaving Drosophila. I further developed a virtual reality paradigm where flies are conditioned to prefer certain orientations within a virtual environment. In dendrites of ellipsoid body neurons, I observe a range of specific visual responses that are modified by this training. Remarkably, I find that distinct calcium responses are observed during presentation of preferred visual features. These studies reveal learning-associated neural activity changes in the inputs to a navigation center of the insect brain.

No description available.

群體行為分析是一個跨學科的研究課題.理解群體協作行為的形成機制，是社會科學和自然科學的根本問題之一.群體行為分析的研究可以為很多關鍵的工程應用提供支持和解決方案，比如智能視頻監控系統，人群異常檢測和公共設施優化.在這篇論文中，說們通過研究和分析真實場景中採集的視頻數據，對群體行為提出了有效的計算框架和算法，來分析這視頻中出現的動態群體模式和行為. / 在第一個章節中，我們提出了一個基於馬爾科夫隨機場的圖模型框架，來分析場景中與群體行為相閥的語羲區域. 這個模型利用馬爾科夫隨機場來聯繫行人軌跡的時空關係，可以從高度分散的行人軌跡中進行數據挖掘，以形成完整的群體行為語義區域.其得到的這些語義區域完整地反映出了不同群體行為的進行模式，具有良好的準確性. 這項研究工作已經在IEEE 計算機視覺和模式識別會議(CVPR)2011 發表. / 為了探索語義區域形成的行為學機制，在第二個章節中，我們提出了一個新穎的動態行人代理人混合模型，來分析擁擠場景中出現的人群動態協作行為.每一種行人協作行為模式被建模成一個線性動態系統，行人在場景中的起始和結束位置放建模成這個動態系統的起始和結束狀態. 這個模型可以從高端分散的行人軌跡中分析出共有的協作行為模式。通過模擬行人的行動決策過程，該模型不僅可以分類不同的群體行為，還可以模擬和預測行人的未來可能路徑和目的地.這項研究工作已經在IEEE 計算機視覺和模式織別會議(CVPR) 2012 作為口頭報告發表. / 在第三個章節中，我們首先在協作動態運動中發現了一個先驗定律: 協作領域關係不變性.根據這個先驗定律，我們提出了一個簡單有效的動態聚類技術，稱為協作濾波器.這個動態聚類技術可以運用在多種動態系統中，並且在高密度噪聲下具有很強的魯棒性.在不同視頻中的實驗證明了協作領域關係不變性的存在以及協作濾波器的有效性.這項研究工作已經投稿歐洲計算機視覺會議(ECCV) 2012. / Crowd behavior analysis is an interdisciplinary topic. Understanding the collective crowd behaviors is one of the fundamental problems both in social science and natural science. Research of crowd behavior analysis can lead to a lot of critical applications, such as intelligent video surveillance, crowd abnormal detection, and public facility optimization. In this thesis, we study the crowd behaviors in the real scene videos, propose computational frameworks and techniques to analyze these dynamic patterns of the crowd, and apply them for a lot of visual surveillance applications. / Firstly we proposed Random Field Topic model for learning semantic regions of crowded scenes from highly fragmented trajectories. This model uses the Markov Random Field prior to capture the spatial and temporal dependency between tracklets and uses the source-sink prior to guide the learning of semantic regions. The learned semantic regions well capture the global structures of the scenes in long range with clear semantic interpretation. They are also able to separate different paths at fine scales with good accuracy. This work has been published in IEEE Conference on Computer Vision and PatternRecognition (CVPR) 2011 [70]. / To further explore the behavioral origin of semantic regions in crowded scenes, we proposed Mixture model of Dynamic Pedestrian-Agents to learn the collective dynamics from video sequences in crowded scenes. The collective dynamics of pedestrians are modeled as linear dynamic systems to capture long range moving patterns. Through modeling the beliefs of pedestrians and the missing states of observations, it can be well learned from highly fragmented trajectories caused by frequent tracking failures. By modeling the process of pedestrians making decisions on actions, it can not only classify collective behaviors, but also simulate and predict collective crowd behaviors. This work has been published in IEEE Conference on Computer Vision and Pattern Recognition (CVPR) 2012 as Oral [71]. The journal version of this work has been submitted to IEEE Transactions on Pattern Analysis and Machine Intelligence (PAMI). / Moreover, based on a prior defined as Coherent Neighbor Invariance for coherent motions, we proposed a simple and effective dynamic clustering technique called Coherent Filtering for coherent motion detection. This generic technique could be used in various dynamic systems and work robustly under high-density noises. Experiments on different videos shows the existence of Coherent Neighbor Invariance and the effectiveness of our coherent motion detection technique. This work has been published in European Conference on Computer Vision (ECCV) 2012. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhou, Bolei. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 67-73). / Abstracts also in Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background of Crowd Behavior Analysis --- p.1 / Chapter 1.2 --- Previous Approaches and Related Works --- p.2 / Chapter 1.2.1 --- Modeling Collective Motion --- p.2 / Chapter 1.2.2 --- Semantic Region Analysis --- p.3 / Chapter 1.2.3 --- Coherent Motion Detection --- p.5 / Chapter 1.3 --- Our Works for Crowd Behavior Analysis --- p.6 / Chapter 2 --- Semantic Region Analysis in Crowded Scenes --- p.9 / Chapter 2.1 --- Introduction of Semantic Regions --- p.9 / Chapter 2.1.1 --- Our approach --- p.11 / Chapter 2.2 --- Random Field Topic Model --- p.12 / Chapter 2.2.1 --- Pairwise MRF --- p.14 / Chapter 2.2.2 --- Forest of randomly spanning trees --- p.15 / Chapter 2.2.3 --- Inference --- p.16 / Chapter 2.2.4 --- Online tracklet prediction --- p.18 / Chapter 2.3 --- Experimental Results --- p.18 / Chapter 2.3.1 --- Learning semantic regions --- p.21 / Chapter 2.3.2 --- Tracklet clustering based on semantic regions --- p.22 / Chapter 2.4 --- Discussion and Summary --- p.24 / Chapter 3 --- Learning Collective Crowd Behaviors in Video --- p.26 / Chapter 3.1 --- Understand Collective Crowd Behaviors --- p.26 / Chapter 3.2 --- Mixture Model of Dynamic Pedestrian-Agents --- p.30 / Chapter 3.2.1 --- Modeling Pedestrian Dynamics --- p.30 / Chapter 3.2.2 --- Modeling Pedestrian Beliefs --- p.31 / Chapter 3.2.3 --- Mixture Model --- p.32 / Chapter 3.2.4 --- Model Learning and Inference --- p.32 / Chapter 3.2.5 --- Algorithms for Model Fitting and Sampling --- p.35 / Chapter 3.3 --- Modeling Pedestrian Timing of Emerging --- p.36 / Chapter 3.4 --- Experiments and Applications --- p.37 / Chapter 3.4.1 --- Model Learning --- p.37 / Chapter 3.4.2 --- Collective Crowd Behavior Simulation --- p.39 / Chapter 3.4.3 --- Collective Behavior Classification --- p.42 / Chapter 3.4.4 --- Behavior Prediction --- p.43 / Chapter 3.5 --- Discussion and Summary --- p.43 / Chapter 4 --- Detecting Coherent Motions from Clutters --- p.45 / Chapter 4.1 --- Coherent Motions in Nature --- p.45 / Chapter 4.2 --- A Prior of Coherent Motion --- p.46 / Chapter 4.2.1 --- Random Dot Kinematogram --- p.47 / Chapter 4.2.2 --- Invariance of Spatiotemporal Relationships --- p.49 / Chapter 4.2.3 --- Invariance of Velocity Correlations --- p.51 / Chapter 4.3 --- A Technique for Coherent Motion Detection --- p.52 / Chapter 4.3.1 --- Algorithm for detecting coherent motions --- p.53 / Chapter 4.3.2 --- Algorithm for associating continuous coherent motion --- p.53 / Chapter 4.4 --- Experimental Results --- p.54 / Chapter 4.4.1 --- Coherent Motion in Synthetic Data --- p.55 / Chapter 4.4.2 --- 3D Motion Segmentation --- p.57 / Chapter 4.4.3 --- Coherent Motions in Crowded Scenes --- p.60 / Chapter 4.4.4 --- Further Analysis of the Algorithm --- p.61 / Chapter 4.5 --- Discussion and Summary --- p.62 / Chapter 5 --- Conclusions --- p.65 / Chapter 5.1 --- Future Works --- p.66

The flash-lag effect is an illusion in which a moving object is perceived advanced beyond an aligned flash. The majority of research into the effect has been directed at specifying its source, though a small body of literature simply makes use of flash-lag to answer diverse questions about perception – without necessarily arbitrating between competing accounts of its nature. The current thesis expands on this little-explored potential of the flash-lag effect with the presentation of three papers reporting programmes of research that exploit the phenomenon to address issues unrelated to its cause. In the first paper it is shown that, like in visual flash-lag, a similar motion direction based anisotropy is evident in the motor version of the effect, in which one's unseen limb is perceived ahead of a flash. Specifically, the effect is greater for motion towards, rather than away from fixation. Furthermore, Paper I also demonstrates for the first time a motor flash-drag effect, in which one's unseen moving hand ‘drags' the perceived position of a nearby flash. It is argued that both of these findings are evidence of parallels between vision and action systems. Paper II takes advantage of the explicitly perceptual nature of the flash-lag effect to investigate whether the visuospatial perception of threatening objects is different to that of non-threatening objects. It is ultimately shown that when a moving stimulus is threatening, the flash-lag effect is greater, regardless of its direction of motion. Paper III shows that gamma movement (the apparent contraction of disappearing stimuli) adds to and subtracts from the forward displacement of contracting and expanding stimuli, respectively. Prior to these papers, however, an overview chapter reviews the flash-lag literature, and argues that the effect can be a useful tool for psychophysics, even without a consensus on its origin.

In order to rapidly get the gist of new scenes or recognise objects, the brain must have mechanisms to process the large amount of visual information which enters the eye. Previous research has shown that observers tend to extract the average feature from briefly seen sets of multiple stimuli that vary along a dimension (e.g., size), a phenomenon called ensemble perception. This thesis investigates ensemble perception of hue. Paper 1 (Maule, Witzel & Franklin, 2014) demonstrates that human observers have memories biased towards the mean hue of a rapidly-presented ensemble of colours. Paper 2 (Maule & Franklin, 2015) further shows that observers are able to identify the mean hue from a distractor fairly reliably, provided the range of hues is manageable. Paper 3 provides evidence that, while observers' settings of the mean hue converge quite closely on the true mean across many trials, the precision of those settings is low and does not support claims that ensemble perception can surpass the limits of visual working memory. Paper 4 found that adults with autism have an enhanced ability to discriminate members from non-members of multi-hue ensembles, and a similar ability to extract the mean hue compared to typical adults, but are worse at averaging small sets. Finally, paper 5 investigated colour afterimages in adults with autism and whether they are affected by top-down gist of a scene. It was found that afterimages were no different in autism compared to a typical group. Overall these studies provide the first comprehensive exploration of ensemble perception of hue, showing that observers can extract and estimate the mean hue of a rapidly-presented multi-colour ensemble with a small hue variance. The ability to average hue may be driven by a sub-sampling mechanism, but results from autistic adults suggests that it can be modulated by processing style.

Visual impairment is a global and potentially devastating affliction. Sensory substitution devices have the potential to lessen the impact of blindness by presenting vision via another modality. The chief motivation behind each of the chapters that follow is the production of more useful sensory substitution devices. The first empirical chapter (chapter two) demonstrates the use of interactive genetic algorithms to determine an optimal set of parameters for a sensory substitution device based on an auditory encoding of vision (“the vOICe”). In doing so, it introduces the first version of a novel sensory substitution device which is configurable at run-time. It also presents data from three interactive genetic algorithm based experiments that use this new sensory substitution device. Chapter three radically expands on this theme by introducing a general purpose, modular framework for developing visual-to-auditory sensory substitution devices (“Polyglot”). This framework is the fuller realisation of the Polyglot device introduced in the first chapter and is based on the principle of End-User Development (EUD). In chapter four, a novel method of evaluating sensory substitution devices using eye-tracking is introduced. The data shows both that the copresentation of visual stimuli assists localisation and that gaze predicted an auditory target location more reliably than the behavioural responses. Chapter five explores the relationship between sensory substitution devices and other tools that are used to acquire real-time sensory information (“sensory tools”). This taxonomy unites a range of technology from telescopes and cochlear implants to attempts to create a magnetic sense that can guide further research. Finally, in chapter six, the possibility of representing colour through sound is explored. The existence of a crossmodal correspondence between (equi-luminant) hue and pitch is documented that may reflect a relationship between pitch and the geometry of visible colour space.