2005.12.22 19:09 "[Tiff] Custom Tags, Private Ifds and other questions", by David Scriven

2005.12.22 23:02 "Re: [Tiff] Custom Tags, Private Ifds and other questions", by David Scriven

On 12/22/05, Chris Cox <ccox@adobe.com> wrote: > The other option is to register a single tag, and put multiple values in > there.

This would be my suggestion too, without knowing too much about what you are actually trying to save. Private IFDs are a bit of a hassle to manipulate with libtiff.

When I first started using TIFFs for this application, I appended a long string to the Description, which my program could then sort out. The problem, I found, is that unlike having a specific tag (eg., wavelength or filter settings) which immediately connected you to what the value meant, you had a long string containing a lot of numbers which were impossible to interpret without the right program. This is the reason I wanted to have specific tags. I do realise that a private Ifd would hide values from people using tiffinfo, and not work when copying images, but I can't say that the single tag is a solution I like, either.

If you look at TIFF images produced by various confocal microscopes they often contain unregistered tags with strings of numbers whose meaning one can only guess at. They also often generate companion files with important information relating to the state under which the data was collected, which, alas often gets separated from the image.

Having suffered in trying to interpret such data, I didn't want to be responsible for inflicting another such botch on the community at large. I would have no problem in sharing the contents of a private Ifd if this is the route I take.

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