2004.09.17 04:39 "Re: [Tiff] BigTIFF Tag Value Count issue", by Chris Cox
The idea was to consume 8 bytes for alignment purposes but use 4 bytes out of those 8 bytes to support the value. Perhaps I misunderstood the problem. I don't have a strong opinion either way, but do believe that the format should be aligned to work well with memory-mapping.
I'm not sure we can guarantee 8 byte alignment of the IFD, so how can we guarantee that the items will be aligned in memory?
Do you think that increasing the count to 8 bytes would be a >problem in libTIFF?
I don't have the libtiff knowledge to properly answer that. If the availability of a native 64-bit storage type can be assumed (pretty safe if 32-bit processors are the new baseline) then it doesn't sound like an 8 byte value would be a problem.
I was thinking more of logic changes necessary. In Photoshop the count field is well isolated - it would take about 80 lines of code to change the count from 4 to 8 bytes. (mostly range checking and increasing the size of loop variables)