OpenCV's RotatedRect angle does not provide enough information

Question

From my experiments, the angle returned by RotatedRect\'s angle variable goes from -90 to 0 degrees, which is not sufficient to determine if the object is leaned to the left

Answer 1

This is what I use (c is my contour). Basically, I get the longest line's du and dv, and then use atan2()

rect = cv2.minAreaRect(c)
box = cv2.boxPoints(rect)
origin = box[0]
rect_width, rect_height = rect[1]
if rect_width > rect_height:
     target = box[3]
else:
     target = box[1]
dv = target[1] - origin[1]
du = target[0] - origin[0]
angle_rads = math.atan2(dv, du)