BigTIFF Design ============== This design details a 64-bit (larger than 4GB) TIFF format specification. The design is based on a proposal by Steve Carlsen of Adobe, with input from various other parties. Briefly ------- * Version = 43 * 8-byte offset to first IFD * Value/Offset fields are 8 bytes * 8-byte offset to the next IFD * add ``TIFFType`` of ``LONG8``, an 8 byte (unsigned) int * ``StripOffsets`` and ``TileOffsets`` and ``ByteCounts`` can be LONG8 More Detail ----------- * The Version ID, in header bytes 2-3, formerly decimal 42, now changes to **43** * Header bytes 4-5 contain the decimal number **8**. * If there is some other number here, a reader should give up. * This is to provide a nice way to move to 16-byte pointers some day. * Header bytes 6-7 are reserved and must be **zero**. * If they're not, a reader should give up. * Header bytes 8-15 contain the 8-byte offset to the first IFD. * Value/Offset fields are 8 bytes long, and take up bytes 8-15 in an IFD entry. * If the value is ≤ 8 bytes, it must be stored in the field. * All values must begin at an 8-byte-aligned address. * 8-byte offset to the Next_IFD, at the end of an IFD. * To keep IFD entries 8-byte-aligned, we begin with an 8-byte (instead of 2-byte) count of the number of directory entries. * Add ``TIFFTypes`` of ``LONG8`` (= 16), an 8 byte (unsigned) int, and ``SLONG8`` (= 17). * Add ``TIFFType`` ``IFD8`` (=18) an 8byte IFD offset. * ``StripOffsets`` and ``TileOffsets`` and ``ByteCounts`` may be ``LONG8`` or the traditionally allowed ``LONG`` or ``SHORT``. * The proposed extension is :file:`.tf8`, and call it "8-Byte TIFF". Otherwise, it's just like "original TIFF." ("TIFF Classic?") Open Issues ----------- * What to call the new format * ChrisCox -- I don't think end users will understand what "8-byte TIFF" means * AndreyKiselev - 23 Sep 2004 -- What about TIFF64? "64" is a widely used buzzword and should be directly associated with the 64-bit offsets and 64-bit architectures. * What 3 character file extension to use (gotta be DOS compatible) * What 4 character file type to use (for Macintosh) * What MIME type to use Samples ------- `Example files `_ from Joris Van Damme. Changes ------- * ``TIFFType`` 13 is ``ttIFD``, 14 is assigned to ``ttUnicode``, and 15 is assigned to ``ttComplex``. So, I changed the types for ``ttLong8`` and ``ttSLong8`` to 16 and 17, respectively. * AndreyKiselev - 23 Sep 2004 -- Where are these fields defined? Is there any new Technical Note or something? And what is encoding behind the word "Unicode"? * ChrisCox - 27 Sep 2004 -- They are in the Adobe TIFF definitions. I am still working on releasing updated TIFF documentation. * Added list of open issues. * settle on version 43 * cleanup * ``TIFFType`` 18 (8 byte IFD) added. * Clarified that fields which may be ``LONG8`` can also be one of the old supported types. See also -------- `AWare Systems' informal overview of the BigTIFF proposal `_.