Most of the time, when working with contours, subjects will have the most diverse shapes, including convex ones. A convex shape is one where there are two points within this shape whose connecting line goes outside the perimeter of the shape itself.
The first facility that OpenCV offers to calculate the approximate bounding polygon of a shape is cv2.approxPolyDP. This function takes three parameters:
A contour
An epsilon value representing the maximum discrepancy between the original contour and the approximated polygon (the lower the value, the closer the approximated value will be to the original contour)
A Boolean flag signifying that the polygon is closed
The epsilon value is of vital importance to obtain a useful contour, so let's understand what it represents. An epsilon is the maximum difference between the approximated polygon's perimeter and the original contour's perimeter. The lower this difference is, the more the approximated...