def _rotatedRectWithMaxArea(w, h, angle):
  """
  Given a rectangle of size wxh that has been rotated by 'angle' (in
  radians), computes the width and height of the largest possible
  axis-aligned rectangle (maximal area) within the rotated rectangle.

  Answer from: https://stackoverflow.com/questions/16702966/rotate-image-and-crop-out-black-borders
  """
  if w <= 0 or h <= 0:
    return 0,0

  width_is_longer = w >= h
  side_long, side_short = (w,h) if width_is_longer else (h,w)

  # since the solutions for angle, -angle and 180-angle are all the same,
  # if suffices to look at the first quadrant and the absolute values of sin,cos:
  sin_a, cos_a = abs(math.sin(angle)), abs(math.cos(angle))
  if side_short <= 2.*sin_a*cos_a*side_long or abs(sin_a-cos_a) < 1e-10:
    # half constrained case: two crop corners touch the longer side,
    #   the other two corners are on the mid-line parallel to the longer line
    x = 0.5*side_short
    wr,hr = (x/sin_a,x/cos_a) if width_is_longer else (x/cos_a,x/sin_a)
  else:
    # fully constrained case: crop touches all 4 sides
    cos_2a = cos_a*cos_a - sin_a*sin_a
    wr,hr = (w*cos_a - h*sin_a)/cos_2a, (h*cos_a - w*sin_a)/cos_2a

  return wr,hr