def triangle(image_draw, offset_x, offset_y, direction, width, height):
  """Show triangle. Direction is -1 (down) or 1 (up)."""
  points = []
  color = None

  if direction==1:
      points = [
          (width/2, 0),  # n
          (0, height), # sw
          (width, height)  # se
      ]
      color = (0, 255, 0) # green
  else:
      points = [
          (width/2, height),  # s
          (0, 0), # nw
          (width,0)  # ne
      ]
      color = (255, 0, 0) # red

  # Draw a filled green triangle
  points = [(x+offset_x, y+offset_y) for (x,y) in points]
  image_draw.polygon(points, fill=color)

