Technical Reports (CIS)

Document Type

Technical Report

Date of this Version

February 1994


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-94-07.


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



Date Posted: 16 July 2007