Bilevel images are not required to have a BitsPerSample or a
SamplesPerPixel tag, while this is unusual these images are still valid.
The test case has been generated by first making a copy of
ccitt3_1d_fill.tiff and then, using `tiffset` to remove both tags:
tiffset -u 258 ccitt3_no_tags.tiff
tiffset -u 277 ccitt3_no_tags.tiff