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June 1999
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1999.06.09 15:52 "Re: Large File Support", by Ed Grissom
In a previous message, Rainer wrote: > Grissom, Ed wrote: > > [...] > > - TIFF magic number changes from "42" to "84" (double 42 ??) > > I'd prefer 66 (= 0x42) or 258 (a base 64 noted number 42) > to keep the meaning behind it > Sounds ok to me. I kind of prefer the 66. That way it would show up as 42 in hex editors. My main point was that it must be changed. > > [...] > > A tag is now made up of 16 bytes, the last field is 8 bytes long, and > > either contains the data (if it will fit in 8 bytes), or an 8 byte > pointer > > to the location of the data. > > If we do changes, our goal should be not to change it again > two years later. So maybe the following changes should also > be done: > > - the Count field of an entry should also be 8 bytes. No one > will use tiles or strips with more than 4 GB data today, > but who knows about tomorrow? > > - the Tag field may be expanded to be 4 bytes to have plenty > of tags left for future enhancements. > > You are right, of course, and I believe that your suggestions were in a previous message that I did not read closely enough. Had I done so, I would have included them in my summary... The count field may be necessary sooner than you think, planar configuration RGB files with 1 line/strip can get a very large count very quickly with SAR data (typically very long but not very wide) -- ed grissom egrissom@ziimaging.com