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A novel edge operator is introduced based on steerable asymmetric linear filters consisting of radial wedge segments. An intensity profile is computed by averaging intensity values along a radial wedge segment as it "sweeps" about a small circular neighborhood. The "steerability" of the filters allows for interpolation of a continuous profile function for n discretely sampled postions of the radial wedge segments. Edge strength is then calculated as a simple difference of conditinal means of the resulting intensity profile. This paper introduces the basic paradigm of using asymmetric filters for low-level image processing tasks and shows how this approach is utilized to design a novel edge operator (the Radial InTensity Edge, or RITE, operator). Features of the RITE operator include: (1) a mathematically simple algorithm with comparable performance to the well-known gradient-based Deriche operator; (2) better performance at points where several edges intersect; (3) an average time complexity reduction by a factor of 1.7 to 2.1 over the Deriche operator.
edge detection, steerable filters, asymmetric filters
Gregory Provan, Hany Farid, and Eero Simoncelli, "A Novel Radial Intensity Based Edge Operator", . February 1994.
Date Posted: 16 July 2007