Learning OpenCV 4 Computer Vision with Python 3 - Third Edition

Detecting lines, circles, and other shapes

Detecting edges and finding contours are not only common and important tasks in their own right; they also form the basis of other complex operations. Line and shape detection walk hand-in-hand with edge and contour detection, so let's examine how OpenCV implements these.

The theory behind line and shape detection has its foundation in a technique called the Hough transform, invented by Richard Duda and Peter Hart, who extended (generalized) the work that was done by Paul Hough in the early 1960s. Let's take a look at OpenCV's API for Hough transforms.