Image analysis – Image enhancement or restoration – Variable threshold – gain – or slice level
Patent
1997-11-24
2000-05-09
Lee, Thomas D.
Image analysis
Image enhancement or restoration
Variable threshold, gain, or slice level
382145, 382149, G06T 550
Patent
active
060614765
ABSTRACT:
A method and apparatus implementing dynamic thresholding techniques in processes that use image subtraction. The subtracted image is separated into a positive difference image using a positive image map and a negative difference image using a negative image map. A positive threshold map and a negative threshold map process a Gaussian filtered first image to generate respective positive and negative dynamic threshold images. The positive and negative threshold map mask out irrelevant areas and implement adaptive gain in pixel thresholds proportional to a difference or contrast between foreground or feature of interest and local background. Dynamic thresholding is a subtraction providing a subtracted positive image and a subtracted negative image. The subtracted positive and subtracted negative images are combined to provide a merged image which is binarized. Edge or Interface detection involves edge detection and true peak detection to find the edge peaks in a pre-image and post image. A binarization map converts edge peak pre and post images and the post image is then dilated to compensate any mis-registration. The dilated post image is subtracted from the binary edge pre-image to form an edge subtraction image. Pixels absent from the post image are assumed to be occluded by a feature of interest. The two binary images are merged, filtered, and connectivity is effected to obtain position and size of contiguous regions of interest.
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Ballard, et al., Computer Vision, Department of Computer Science, University of Rochester, Rochester, NY, pp. 1-103, 1982.
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Cognex Corporation
Lee Thomas D.
Michaelis Brian L.
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