2004.04.15 12:23 "Re: [Tiff] Large TIFF files", by Dan Smith
I'm not very au courant with any of this, but I vaguely supposed that TIFF/IT allows for some kind of wrapper specification that includes the equivalent of an arbitrary number of TIFF files, with a coordinate offset for each. That is, a TIFF/IT file can glue together the data from an arbitrary number of individual TIFF files, and is thus capable of representing images of enormous size.
If this is correct, it would seem that one approach would be to define a restricted subset of TIFF/IT for the specific purpose of supporting >4G single images. The purpose of the restrictions would be to allow for direct support for the format in libtiff, without requiring libtiff to handle general TIFF/IT files.
(If I'm totally out to lunch in this, my apologies).