scale images

def scale_to_fit(image, frame, enlarge=False):
    image_width, image_height = image
    frame_width, frame_height = frame
    image_aspect = float(image_width) / image_height
    frame_aspect = float(frame_width) / frame_height
    # Determine maximum width/height (prevent up-scaling).
    if not enlarge:
        max_width = min(frame_width, image_width)
        max_height = min(frame_height, image_height)
    else:
        max_width = frame_width
        max_height = frame_height
    # Frame is wider than image.
    if frame_aspect > image_aspect:
        height = max_height
        width = int(height * image_aspect)
    # Frame is taller than image.
    else:
        width = max_width
        height = int(width / image_aspect)
    return (width, height)