allow both tif and tiff for TIFF images

    # Note

    # ----

    #   For the following file

    #       20191030_ironman_small_0070_300_440_0520.tiff

    #       20191030_ironman_small_0070_300_440_0520.tif(f)

    #   the rotation angle is 300.44 degrees

    # If all given filenames follows the pattern, we will use the angles from

    # filenames. Otherwise, we will use the angles from metadata.

    regex = r"\d{8}_\S*_\d{4}_(?P<deg>\d{3})_(?P<dec>\d{3})_\d*\.tiff"

    regex = r"\d{8}_\S*_\d{4}_(?P<deg>\d{3})_(?P<dec>\d{3})_\d*\.tif{1,2}"

    matches = [re.match(regex, Path(f).name) for f in filelist]

    if all(matches):

        logger.info("Using rotation angles from filenames.")

        rotation_angles = np.array([float(".".join(m.groups())) for m in matches])

    else:

        # extract rotation angles from metadata

        file_ext = set([Path(f).suffix for f in filelist])

        if file_ext != {".tiff"}:

            logger.error("Only tiff files are supported.")

            raise ValueError("Rotation angle from metadata is only supported for Tiff.")

        file_exts = set(Path(f).suffix.lower() for f in filelist)

        if not file_exts.issubset({".tiff", ".tif"}):

            logger.error("Only .tiff and .tif files are supported.")

            raise ValueError("Rotation angle from metadata is only supported for .tiff and .tif files.")

        # -- read metadata

        # img = tifffile.TiffFile("test_with_metadata_0.tiff")

        # img.pages[0].tags[65039].value