Merge remote-tracking branch 'upstream/3.4' into merge-3.4

def nothing(dummy):

    pass

def draw_motion_comp(vis, (x, y, w, h), angle, color):

def draw_motion_comp(vis, rect, angle, color):

    x, y, w, h = rect

    cv.rectangle(vis, (x, y), (x+w, y+h), (0, 255, 0))

    r = min(w/2, h/2)

    cx, cy = x+w/2, y+h/2

    r = min(w//2, h//2)

    cx, cy = x+w//2, y+h//2

    angle = angle*np.pi/180

    cv.circle(vis, (cx, cy), r, color, 3)

    cv.line(vis, (cx, cy), (int(cx+np.cos(angle)*r), int(cy+np.sin(angle)*r)), color, 3)

        prev_frame = frame.copy()

        if 0xFF & cv.waitKey(5) == 27:

            break

    # cleanup the camera and close any open windows

    cam.release()

    cv.destroyAllWindows()