Apparatus and method for detecting and sub-pixel location of edges in a digital image

  • US 6,408,109 B1
  • Filed: 10/07/1996
  • Issued: 06/18/2002
  • Est. Priority Date: 10/07/1996
  • Status: Expired due to Term
First Claim
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1. An apparatus for detection and sub-pixel location of edges in a digital image, said digital image including a plurality of pixel values, each pixel value being associated with a respective pixel point of a regularly-spaced pixel grid, said apparatus comprising:

  • a gradient estimator for estimating gradient magnitude and gradient direction at a plurality of regularly-spaced gradient points in said digital image, so as to provide a plurality of estimates of gradient magnitude and gradient direction, each said estimate of gradient magnitude and gradient direction being associated with a respective gradient point of a regularly-spaced gradient grid;

    a peak detector, cooperative with said gradient estimator, operating such that gradient direction associated with each gradient point is used to select a respective set of neighboring gradient points, and operating such that gradient magnitude associated with each gradient point is compared with each gradient magnitude of said respective set of neighboring gradient magnitudes so as to determine which of said gradient magnitudes is a local maximum of gradient magnitude in approximately said gradient direction; and

    a sub-pixel interpolator, cooperative with said peak detector, operating such that said local maximum of gradient magnitude and a set of neighboring gradient magnitudes are used to determine an interpolated edge position along a one-dimensional gradient magnitude profile including a gradient point associated with said local maximum of gradient magnitude and each gradient point associated with said set of neighboring gradient magnitudes.

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