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July 2009
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2009.07.10 14:59 "Re: TIFFTAG_RICHTIFFIPTC definition", by Gary Mcgath
"Joris Van Damme \(AWare Systems\)" <info@awaresystems.be> wrote: >> Please can someone tell me why the TIFFTAG_RICHTIFFIPTC tag is defined as >> using type TIFF_LONG? The information is actually an array of bytes not >> longs so swapping the bytes if the byte order of the computer and file >> differ corrupts the data. > > You're right. This is a historical mistake, and it leads to trouble. > > My humble advice when it comes to writing is using the datatype TIFF_BYTE or > TIFF_UNDEFINED. The latter is probably the most 'correct' as it literaly > signifies that the data is of mixed type and byte order and widths of data > members is defined outside the scope of TIFF. The datatype TIFF_BYTE can be > used as amounting to the same thing, though, mostly. This raises the old issue of verifying a format by the book vs. verifying it by "reasonable" usage. JHOVE, by a policy which was set from its inception, checks format compliance by the book; thus, correcting the data type for TIFFTAG_RICHTIFFIPTC will make JHOVE say the file is invalid. I'm becoming steadily more convinced that by-the-book validation isn't the best approach, perhaps especially for TIFF, where Adobe hasn't revised "the book" in well over a decade. I've already implemented some compromises; this may be one more I should add. -- Gary McGath Digital Library Software Engineer Harvard University Library Office for Information Systems http://hul.harvard.edu/~gary/index.html