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July 2007
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2007.07.05 13:23 "Re: Tiff Digest, Vol 38, Issue 12", by Gary Mcgath
John Aldridge wrote: > Joris wrote: >> 1) BigTIFF is TIFF. > > No it's not :-) It's not in the TIFF specification > > http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf > > which also claims that TIFF is an Adobe trademark, so presumably they > are the people entitled to specify it! There's a bit of revisionism in the BigTIFF description. The proposal on awaresystems.be refers to the value at offset 2 as a "Version number," which is 42 for "classic TIFF" and 43 for BigTIFF. Yet the TIFF 6.0 specification says that at bytes 2-3 the value is 42, which is "An arbitrary but carefully chosen number (42) that further identifies the file as a TIFF file." This is NOT a version number. TIFF is annoying in that there is no version number specification; you can tell what version was used to write a TIFF file only by what features are used. But putting the number 43 at offset 2 is a statement that the file is not any version of TIFF. Since BigTIFF diverges from the specification to distinguish itself from TIFF, it should be considered not a version of TIFF, but as a different file format (albeit one derived from TIFF). -- Gary McGath Digital Library Software Engineer Harvard University Library Office for Information Systems http://hul.harvard.edu/~gary/index.html