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May 2005
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2005.05.20 16:08 "TIFF/EP and TIFF 6.0", by Bob Young
I'm new to this list and have a couple of questions. I'm updating the TIFF capture and playback routines of digital camera firmware. I'd like to add a thumbnail image to the TIFF files saved by the firmware. I've read both the TIFF 6.0 spec, and the TIFF/EP spec. One difference between TIFF/EP and TIFF 6.0 appears to be which IFD is used for the thumbnail image. TIFF/EP recommends the thumbnail be described by IFD0, and TIFF6 requires that IFD1 be used, as IFD0 must be the main image. The code is flexible enough to do it either way, but I was surprised to find that when I opened a TIFF/EP image (denoted by having a TIFF/EPStandardID tag in IFD0) in PhotoshopCS, it displayed the thumbnail instead of the main image. I would have thought that if any APP were TIFF/EP "Aware" it would have been Adobe. Is there something I'm not understanding? Secondly, regardless of whether the thumb is placed in IFD0 or IFD1, is it legal for the thumb to be of a different photometric interpretation than the main image, specifically can I use a YCbCr thumb with a RGB main image? Thanks for any responses Bob Young