We present a generalized extensible framework for automated recognition of swarming activities in video sequences. The trajectory of each individual is produced by the visual tracking sub-system and is further analyzed to detect certain types of high-level grouping behavior. We utilize recent findings in swarming behavior analysis to formulate a problem in terms of the specific distance function that we subsequently apply as part of the two-stage agglomerative clustering method to create a set of swarming events followed by a set of swarming activities. In this paper we present results for one particular type of swarming: shopper grouping. As part of this work the events detected in a relatively short time interval are further integrated into activities, the manifestation of prolonged high-level swarming behavior. The results demonstrate the ability of our method to detect such activities in congested surveillance videos. In particular in three hours of indoor retail store video, our method has correctly identified over85% of valid '"shopper-groups'" with a very low level of false positives, validated against human coded ground truth.

The paper presents a fusion-tracker and pedestrian classifier for color and thermal cameras. The tracker builds a background model as a multi-modal distribution of colors and temperatures. It is constructed as a particle filter that makes a number of informed reversible transformations to sample the model probability space in order to maximize posterior probability of the scene model. Observation likelihoods of moving objects account their 3D locations with respect to the camera and occlusions by other tracked objects as well as static obstacles. After capturing the coordinates and dimensions of moving objects we apply a pedestrian classifier based on periodic gait analysis. To separate humans from other moving objects, such as cars, we detect, in human gait, a symmetrical double helical pattern, that can then be analyzed using the Frieze Group theory. The results of tracking on color and thermal sequences demonstrate that our algorithm is robust to illumination noise and performs well in the outdoor environments.

This paper outlines the theoretical background and presents a new approach to human body tracking with monocular static camera. A novel "view-based representation" is introduced at the feature extraction stage. We show that ambiguities in correspondence, such as the ones that occur as the result of occlusion, can be resolved by using this approach. In particular, we store color information for each object in a vector of views, where the number of elements is determined online, using unsupervised clustering followed by the cluster validity assessment. Based on this representation a tracking system was developed. The prelimiary results presented show the discriminative potential of the proposed system.

This paper describes a pattern recognition approach to determine readability of text labels in augmented reality systems. In many augmented reality applications, one of the ways in which information is presented to the user is to place a text label over the area of interest. However, if this information is placed over very busy and textured backgrounds, this can affect the readability of the text. The goal of this work was to identify methods of quantitatively describing conditions under which such text would be readable or unreadable. We used texture properties and other visual features to determine if a text placed on a particular background would be readable or not. Based on these features, a supervised classifier was built that was trained using data collected front human subjects' judgment of text readability. Using a rather small training set of about 400 human evaluations over 50 heterogeneous textures the system is able to achieve a correct classification rate of over 85%.

Automatic classification of an image as a photograph of a real-scene or as a painting is potentially useful for image retrieval and Web site filtering applications. The main contribution of the paper is the proposition of several features derived from the color, edge, and gray-scale-texture information of the image that effectively discriminate paintings from photographs. For example, we found that paintings contain significantly more pure-color edges, and that certain gray-scale-texture measurements (mean and variance of Gabor filters) are larger for photographs. Using a large set of images (12000) collected from different Web sites, the proposed features exhibit very promising classification performance (over 90%). A comparative analysis of the automatic classification results and psychophysical data is reported, suggesting that the proposed automatic classifier estimates the perceptual photorealism of a given picture.

We compare the properties of intensity and color edges in photographs of real scenes and paintings. We demonstrate that paintings contain significantly more color-only edges, whereas the amount of intensity-only edges does not differ significantly between the two classes. In addition, color edge strength is significantly higher for paintings. The differences between paintings and photographs are more accentuated when high-resolution, losslessly compressed images are used. These distinguishing features can be used for the automatic differentiation between the two classes of images.