Sample Edge

The Sample Edge module provides a way to detect edges along a specified path. The path is a single line that you can manually place on the image or control the position using variables. The edges detected are then saved into a variable for later usage. Note that the detected edges are with respect to the line angle.

This module is useful for detecting the placement of a particular object within an image or to detect that a certain number of edges need to be present in the form of a component quality assurance.

Interface

Instructions

1. Current Image - move the line to the location along which you want to sample for edges. You can use the red square to move the entire line, the endpoint squares to move each endpoint individually or change the coordinates using the text boxes below in the Coordinates area.

2. Identify - select how many edges you want to detect. Note that if you select many edges to be identified you are not guaranteed to get that many edges depending on the thresholding information below. The "Identify" number specifies a maximal number of edges to detect. Note that detected edges are ordered with respect to the edge intensity at each point.

3. Smooth Edge - to reduce noisy edges select the amount of smoothing that should be applied to the edge prior to edge detection.

4. Edge Isolation - to avoid edges from bunching up together select how many pixels each edge should be isolated from the next detected edge.

5. Edge Threshold - to eliminate very weak edges select an appropriate edge threshold (0-255) that will remove edges whose edge intensity is below the threshold. Note that smoothing the edge will also reduce the edge intensity and thus the Edge Threshold will need to be adjusted after the smoothness is specified.

6. Relative Threshold - to only select those edges that are significant you can specify the relative threshold (0-100) that will remove successive edges that are the relative threshold percent less than the previous edge. For example, consider the highest 3 edge values as 130, 120 and 40. If the relative threshold is 50% then the last edge 40 would be eliminated since 40 is less than 50% of 120. As 120 is 92% of 130 it is not eliminated (unless the threshold where set at 95%).

7. Show Edges - to visually see which edges are detected select the appropriate Shape, Color and Size of the marker that will indicate where in the image the edges have been detected.

Note

To control the line location using variables specify the variable as [variable_name] within the coordinate textboxes.

Example

The detected edges marked with red squares using the configuration shown in the above screenshot.
Connecting usb cable to Sabertooth

Variables

SAMPLED_EDGES - an x,y array of the location of the detected edges.