One implementation of DPX (SMPTE ST 268) and Kodak Cineon for the apps that
each carried their own: PhotoCraft (reader, writer, Cineon, header metadata),
FilmCraft (Y'CbCr descriptors, ABGR, packed 10/12-bit) and EffectCraft
(Cineon in both byte orders, pixel aspect ratio, 12-bit method B).
The crate returns code values and header fields; colour conversion and
orientation stay in the apps.
