Image analysis – Pattern recognition – Feature extraction
Patent
1998-01-08
2000-02-01
Chang, Jon
Image analysis
Pattern recognition
Feature extraction
382203, G06K 946
Patent
active
060212225
ABSTRACT:
The present invention generally relates to pattern recognition systems, and particularly to the detection of a circle from a complex image that combines circles, straight lines, and other shapes. The system of the invention determines whether a pixel in an image being scanned is an edge pixel, and derives a gradient vector associated with the edge pixel. The direction of the gradient vector is modified toward a center of a circle incorporating the edge pixel, and then whether the edge pixel is a circle edge pixel is determined. If the edge pixel is a circle edge pixel, coordinates of a center of a circle for the edge pixel are calculated, and stored in memory. After the above steps are repeated for the other pixels in the image being scanned, the system determines whether coordinates of a calculated center of a circle for any circle edge pixel are the same for other circle edge pixels. If so, a circle is considered to be detected based on the circle edge pixels having calculated centers within a predetermined range of each other and within a predetermined frequency of occurrence.
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Chang Jon
Ricoh Co. Ltd.
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