Importance

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Abstract

A method and apparatus for determining the location and orientation of a reference feature in an image is provided. At train-time, a template image is created for use during the run-time phase. At run-time, a reference feature is located by first determining the principal angle of the reference feature. In a preferred embodiment, the principal angle .theta. of the reference feature is found by partitioning the reference feature into a plurality of regions, projecting each of the regions at 0.degree., and performing template matching with a template image to determine the position of a plurality of points along a principal axis of the reference feature. Then, either an equation of a 'best fit' line can be calculated and solved simultaneously with an equation of a horizontal reference line, or the reference feature image can be projected at the angle of the 'best fit' line to obtain a one-dimensional reference image which can be matched to the one-dimensional template image to find the relative displacement between them that maximizes a match-metric value. The invention is particularly useful for determining the location and orientation of reference feature images that have been degraded in some way. The invention provides substantial immunity to such image degradation by comprehensively exploiting image information derived from the entire image of the reference feature.

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First Claim