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Subject: Re: [Tiff] Large TIFF files
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Thread-Topic: [Tiff] Large TIFF files
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From: "Gerben Vos" <gerben@ZyLAB.COM>
To: "Tiff mailing list" <tiff@remotesensing.org>
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Date: Thu, 22 Apr 2004 12:32:33 +0200
X-UIDL: 41fdb733d171016b7ce9ee6e52af3f4b

Hi,

neither I nor the company I work for seem to have a stake in a 64-bit
TIFF format in the foreseeable future, but I hope I may mutter a bit
from the sideline occasionally. :-)

Being the most evolutionary approach, I would like to see Frank's
proposal being discussed a bit more.

>   o Introduce a new data type TIFF_LONGLONG = 14 which is a 64 bit
>     integer value.
>   o Allow as a non-core extention the option of having the strip
>     offsets or tile offsets as TIFF_LONGLONG.
>   o leave everything else the same.

This means that all directories and ancillary data must be forced below
the 4GB limit, which makes writing the TIFF harder. On the other hand,
TIFF reading apps can be upgraded almost trivially. (This seems a bit
against the current TIFF philosophy, which makes writing easy and
reading hard.)

We could introduce a tag similar to SubIFD (330) to point to a directory
in 64-bit space, but that would be adding to the cruft.

If we take a more revolutionary approach, I think we should liberally
borrow ideas from the PNG spec, like their ASCII-transfer-detecting
header and the bit that indicates whether unknown tags should be copied.
Also in that case, I would slightly prefer ASCII-like tags, it gives my
eyes something to hang on to when viewing a TIFF in a hex editor (which
will remain useful for corrupted files and derived-but-not-quite-TIFF
formats like Microsoft's Office Document Imaging format).

I'm sure Chris will bring in the lessons they've learned at Adobe when
creating their PSB/Large Document Format.

Also, W3 5H00LD K4LL 7H3 F1L3 F0RM47 BIFF!!!!!!!!111!!!! CU2 B1FF R00L2
4ND H3'Z L33T!!!!!!!!11111111!!!!!!!!!!!!!!!!

(Sorry, couldn't let that bit of Usenet history pass by.)

					Gerben Vos.
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