BigTIFF Design

This is the HTML equivalent of a former Wiki working place for preparing 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 ".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 Steve Carlsen

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.