Scale the two images to [0, 1] based on min/max from both.

def scale_images_0to1(slice1, slice2):
    """Scale the two images to [0, 1] based on min/max from both."""

    min_value = max(slice1.min(), slice2.min())
    max_value = max(slice1.max(), slice2.max())

    slice1 = (slice1 - min_value) / max_value
    slice2 = (slice2 - min_value) / max_value

    return slice1, slice2