Caching internet data is an application that illustrates data structure speed. I have developed a sequence of assignments for teaching about lists, hash tables and trees using caches for internet sourced stock prices.

This Tips and Techniques sections will demonstrate that teaching about queues implemented as circularly linked lists becomes easy when an extra link is used.

A constrained contour is an outline of a region of interest, obtained by linking the possible edge points under the constraints of connectivity, smoothness, image context, and an externally specified approximate contour. A constrained contouring algorithm in polar coordinates that traces closed contours using their rough approximations is discussed. A set of locally optimal contour locations (LOCLs) is found in all the selected radial directions by analyzing the image features and the external constraints. A graph search based algorithm is used to select a smooth contour that passes through the maximum number of LOCLs.>

The human face is an object that is easily located in complex scenes by humans and adults alike. Yet the development of an automated system to perform this task is extremely challenging. This paper is about developing computational procedures to locate human faces in newspaper photographs where scenes are often cluttered making object location non-trivial. On the other hand, the task is made feasible by constraints which follow naturally from rules in photo-journalism. Faces identified by the caption are clearly depicted without occlusion and contrast against the background and sizes of faces fall within a fixed range depending on the dimensions of the photograph and the number of people featuring in it.>

Presents preliminary results from an investigation of edge detection with a principal components analysis. In this way the parameters of an edge detector can be derived from data about edges in images. The preliminary investigations study how the optimal region of interest varies with the size of objects in the image.>

The authors adopted a model-based approach, where the shape of the object is defined in terms of several mini-templates. The mini-templates are abstract descriptions of simple geometric features like arcs and corners. Relationships between mini-templates are not rigid. Rather, they are represented by springs that allow deformation of a template in terms of its size and orientation. Cost functionals are determined empirically. The authors expect their system to generate candidate regions in a given photograph associated with a rank of its goodness.>

An empirical investigation of the importance of accurate assessment of prior probabilities in a typical visual classification problem, handwritten ZIP code recognition, is presented. Prior probabilities for individual digits and entire ZIP codes were investigated; the results for priors of individual digits are summarized. In studies of prior distributions over entire ZIP codes, it was found that the qualitative information had a major effect on the efficacy of the algorithm, whereas quantitative information was relatively unimportant. It is concluded that precise estimation of prior probabilities is unnecessary in the domain of computer vision, whereas accurate qualitative assessment of possibilities is important.>

A computational approach to locating human faces in newspaper photographs is described. While the computational recognition of a well-framed face as one of a known set of faces has received some attention, the computational location of faces in varying contexts is relatively unexplored. Candidates for the locations of faces are hypothesized by extracting features in the edge-image of the photograph and matching with a model of a face profile. A face is defined by a parametric representation of each of the component parts. Knowledge contained in the caption is represented using semantic networks and is used to reason about the locations of faces of individuals in the photograph.>