Canny Algorithm

Canny Edge Detection
09gr820 March 23, 2009

1

Introduction

The purpose of edge sensing in general is to signi? goattly reduce the amount of data in an witness, while preserving the structural properties to be used for foster figure processing. Several algorithms exists, and this worksheet focuses on a particular one demonstrable by John F. Canny (JFC) in 1986 [2]. Even though it is quite old, it has become one of the standard edge maculation methods and it is still used in research [3] [1]. The aim of JFC was to spring up an algorithm that is best with regards to the following criteria: 1. Detection: The probability of sensing genuinely edge points should be maximized while the probability of wrongly detecting non-edge points should be minimized. This corresponds to maximizing the signal-to-noise ratio. 2. Localization: The spy edges should be as close as possible to the real edges. 3. Number of responses: One real edge should not consequence in more than one detected edge (one can argue that this is implicitly included in the ?rst requirement). With JFCs numeric formulation of these criteria, Cannys Edge Detector is optimal for a certain class of edges (known as step edges). A C++ implementation of the algorithm has been written, and this will be further described in Section 3.



The images used throughout this worksheet are generated using this implementation.

1.1

Test Image

The image in Figure 1 is used throughout this worksheet to demonstrate how Canny edge spotting works. It depicts a partially assembled pump from Grundfos, and the edge detection is a step in the process of estimating the pose (position and orientation) of the pump. The image has been preprocessed as described in the worksheet Ideas for Solution to the Pose Estimation line. The preprocessing includes: Determining ROI (Region of Interest) that includes only white background besides the pump, and cropping the image to this region. Conversion to gray-scale to limit the...If you want to get a integral essay, order it on our website: Orderessay



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