Report Number: CS-TR-73-386
Institution: Stanford University, Department of Computer Science
Title: A corner finder for visual feedback.
Author: Perkins, W. A.
Author: Binford, Thomas O.
Date: August 1973
Abstract: In visual-feedback work often a model of an object and its approximate location are known and it is only necessary to determine its location and orientation more accurately. The purpose of the program described herein is to provide such information for the case in which the model is an edge or corner. Given a model of a line or a corner with two or three edges, the program searches a TV window of arbitrary size looking for one or all corners which match the model. A model-driven program directs the search. It calls on another program to find all lines inside the window. Then it looks at these lines and eliminates lines which cannot match any of the model lines. It next calls on a program to form vertices and then checks for a matching vertex. If this simple procedure fails, the model-driver has two backup procedures. First it works with the lines that it has and tries to form a matching vertex (corner). If this fails, it matches parts of the model with vertices and lines that are present and then takes a careful look in a small region in which it expects to find a missing line. The program often finds weak contrast edges in this manner. Lines are found by a global method after the entire window has been scanned with the Hueckel edge operator.