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January 2007
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2007.02.01 20:02 "Re: Interpreting SubIFDs tag", by Joris Van Damme
Phil, Phil Harvey wrote: > > I'm talking of the specification of the concept *tag*. A tag can > > have an array of values. SubIFD is a tag. The SubIFD specification > > should not be able to overwrite that behaviour localy. > > Yes, I agree that *any* tag can have any number of values. But don't > we have to apply a degree of restraint here to try to adhere to the > original intent of the tag definition? Otherwise it becomes a bit of > a free-for-all. > > But maybe that ship has sailed. Be conservative in what you write, and liberal in what you read. Yes, certainly the ship has sailed. You yourself pointed out Adobe writes both flavours. LibTiff writes arrays of SubIFDs rather then lists, but the support for doing that is so badly known that people have hacked into it and made it do anything. AsTiff (my own) writes lists, by default, but can be made to write and array of values (I included that for testfile generation purpose since I hope to one day base a sort-off complete TIFF testfile generator on my codec). The ship has sailed. That's no problem, though. It's not the first time something like this happens. In general, anything that is unambigious, goes, as far as a TIFF reader is concerned. And this certainly is perfectly unambigious. Best regards, Joris