Create the cache file name.

def cache_fname(img, backend, light, cache_dir, sat=""):
    """Create the cache file name."""
    color_type = "light" if light else "dark"
    file_name = re.sub("[/|\\|.]", "_", img)
    file_size = os.path.getsize(img)

    file_parts = [file_name, color_type, backend,
                  sat, file_size, __cache_version__]
    return [cache_dir, "schemes", "%s_%s_%s_%s_%s_%s.json" % (*file_parts,)]