def convert_mask_to_polygon(mask):
contours = None
if int(cv2.__version__.split('.')[0]) > 3:
contours = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_TC89_KCOS)[0]
else:
contours = cv2.findContours(mask, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_TC89_KCOS)[1]
contours = max(contours, key=lambda arr: arr.size)
if contours.shape.count(1):
contours = np.squeeze(contours)
if contours.size < 3 * 2:
raise Exception('Less then three point have been detected. Can not build a polygon.')
polygon = []
for point in contours:
polygon.append([int(point[0]), int(point[1])])
return polygon