def darker(image1, image2):
    """
    Compares the two images, pixel by pixel, and returns a new image containing
    the darker values. At least one of the images must have mode "1".

    .. code-block:: python

        out = min(image1, image2)

    :rtype: :py:class:`~PIL.Image.Image`
    """
    image1.load()
    image2.load()
    return image1._new(image1.im.chop_darker(image2.im))
