Check if two contours intersect?

Question

I have 2 contours (cont1 and cont2) received from cv2.findContours(). How do I know if they intersect or not? I don\'t need coordinate

Answer 1

The answer by nathancy works, but suffers on the performance side where as in the example creates 3 copies of the image to draw the contours thus, is sluggish when it comes to execution time.

My alternative answer is as below;

def contour_intersect(cnt_ref,cnt_query, edges_only = True):

    intersecting_pts = []

    ## Loop through all points in the contour
    for pt in cnt_query:
        x,y = pt[0]

        ## find point that intersect the ref contour
        ## edges_only flag check if the intersection to detect is only at the edges of the contour

        if edges_only and (cv2.pointPolygonTest(cnt_ref,(x,y),True) == 0):
            intersecting_pts.append(pt[0])
        elif not(edges_only) and (cv2.pointPolygonTest(cnt_ref,(x,y),True) >= 0):
            intersecting_pts.append(pt[0])

    if len(intersecting_pts) > 0:
        return True
    else:
        return False