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The first-order differential invariants of optic flow, namely divergence, curl, and deformation, provide useful shape indicators of objects passing through view. However, as differential quantities these are often difficult to extract reliably. In this paper we present a filter-based method for computing these invariants with sufficient accuracy to permit the construction of a partial scene model...
Image averaging can be performed very efficiently using either separable moving average filters or by using summed area tables, also known as integral images. Both these methods allow averaging to be performed at a small fixed cost per pixel, independent of the averaging filter size. Repeated filtering with averaging filters can be used to approximate Gaussian filtering. Thus a good approximation...
This paper shows that most surveillance cameras fall well short of providing sufficient image quality, in both spatial resolution and colour reproduction, for the reliable identification of faces. In addition, the low resolution of surveillance images means that when compression is applied the MPEG/JPEG DCT block size can be such that the spatial frequencies most important for face recognition are...
For geoscientific applications, automatic shape-based feature detection offers a fast and non-subjective means of identifying geological structures within data. Most previously published examples of circular feature detection for geoscientific applications aimed to identify impact craters from optical or topographic data. Various techniques used include the Hough transform, template matching, and...
Transformation of image patches is a common requirement for 2D transition animations such as shape interpolation and image morphing. It is usually done by applying affine transformations to triangular patches. However, the affine transformation does not model the perspective transformation frequently found in images. Hence, such techniques can only produce approximate results and usually use an excessively...
This paper addresses the problem of deducing the surface shape of an object given just the surface normals. Many shape measurement algorithms such as shape from shading and shape from texture only return the surface normals of an object, often with an ambiguity of pi in the surface tilt. The surface shape has to be inferred from these normals, typically via some integration process. However; reconstruction...
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