National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 62)

Chapter 5 Performing Machine Vision Tasks
IMAQ Vision for LabWindows/CVI User Manual 5-10 ni.com
Finding Lines or Circles
If you want to find points along the edge of an object and find
a line describing the edge, use
imaqFindEdge() and
imaqFindConcentricEdges() . The imaqFindEdge() function finds
edges based on rectangular search areas, as shown in Figure 5-5. The
imaqFindConcentricEdge() function finds edges based on annular
search areas.
Figure 5-5. Finding a Straight Feature
1 Search Region
2 Search Lines
3 Detected Edge Points
4 Line Fit to Edge Points
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1
4
3