A hierarchy of feature types are employed to detect motion, establish temporal tracks and fuse motion information from multiple cameras. The development of such a hierarchy has been motivated by applications which req...
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A hierarchy of feature types are employed to detect motion, establish temporal tracks and fuse motion information from multiple cameras. The development of such a hierarchy has been motivated by applications which require the tracking of objects in open space environments such as car parks or shopping malls. Such applications include security monitoring of sites, the monitoring of vehicles entering, manoeuvring, parking and leaving carparks, and the generation of marketing data in shopping malls from the automatic analysis of shoppers' browsing behaviour. Establishing correspondences between features in images is difficult as low level features tend to exhibit stable statistics over very short intervals and may temporarily disappear because of occlusion and low contrast with the background. The tracking process may be improved and a high degree of long term motion stability obtained by introducing the concept of hierarchy. In addition, fusing information from different viewpoints is more appropriate at higher data representations. The paper describes a hierarchy of features used to establish a scene description.
When a Voronoi diagram is constructed incrementally, the quaternary-tree bucketing method of Ohya et. al. provides a useful way of spreading out the insertion order of the generator sites and obtaining initial guesses...
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When a Voronoi diagram is constructed incrementally, the quaternary-tree bucketing method of Ohya et. al. provides a useful way of spreading out the insertion order of the generator sites and obtaining initial guesses for the place to insertion them. This reduces the average time complexity of constructing Voronoi diagrams for n generator sites from O(n/sup 2/) to O(n). We extend Ohya's method to support the construction of multi-scale Voronoi diagrams, using generator sites that have a discrete scale-value, such as those produced by scale-space image analyses. In order to produce a Voronoi diagram at each scale-level, the original bucketing method needed to be repeatedly re-run and produced less efficient insertion orders and initial guesses for the generators. The new method efficiently builds one Voronoi diagram, starting with the set of coarsest scale generators, then adds details in decreasing order of significance. After an introduction and brief summary of Ohya's method we describe the new algorithm and some example results. The work may have application in both computervision and computer graphics or visualisation.
The authors considered a multi-resolution, model based segmentation method for magnetic resonance angiography (MRA). It is a spatial domain based technique and an extension to 3D of a 2D curve segmentation method repo...
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The authors considered a multi-resolution, model based segmentation method for magnetic resonance angiography (MRA). It is a spatial domain based technique and an extension to 3D of a 2D curve segmentation method reported elsewhere. The method has been demonstrated to produce a concise symbolic description of the MRA data (in the form of vessel centre lines) and is efficient in its computational complexity being equivalent in processing to filtering by a 3*3*3 kernel, and based on a generalised and flexible image model which has great potential as a basis for both qualitative and quantitative assessment of MRA data. The work and results presented thus far are preliminary and currently there are several areas where consolidation and enhancement is necessary. There is a need to assess the levels of noise in the data in situ, to better control the confidence levels used for the hypothesis testing. Curve tracing is currently done probabilistically based purely on the local curvature. By considering the physical measurements of the data being imaged, e.g. speed of blood and the vessel diameters, local connectivity could be established using a conservation of mass constraint. Also, there is need to explicitly define bifurcations as part of the signal model. With regards to visualisation, some experimentation has already been carried out to represent flow direction and using the multiresolution vectors for generating filtered maximum intensity projections and predicting probable flow. The segmentation is also being applied to the estimation of blood pressure gradients in vivo.
Digital imageprocessing is a rapidly evolving field with growing applications in science and engineering. The paper addresses the fundamentals of major topics of digital imageprocessing and computervision. The defi...
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Digital imageprocessing is a rapidly evolving field with growing applications in science and engineering. The paper addresses the fundamentals of major topics of digital imageprocessing and computervision. The definitions of pattern recognition, image understanding, computer and machine vision are briefly discussed. Typical problems in imageprocessing and computervision applications are also described including smoothing, enhancement, restoration, filtering, data compression, shape analysis, region analysis, sequence analysis, feature extraction, detection and identification, spectral estimation and factorization and synthesis.
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