2012.11.24 00:09 "[Tiff] help writing thumbnails to TIFF file?", by Paul Heckbert

2012.12.13 16:41 "Re: [Tiff] IFD offset tags written with wrong DataType in libtiff 4.0.3", by Paul Heckbert

Yes, that's what I meant: use TIFFDataType IFD8 (or maybe LONG8?) for BigTIFF files and LONG (not IFD) for Classic TIFF, and that's what my code change implements.

On 2012/12/13, at 9:50 AM, Bob Friesenhahn wrote:

On Wed, 12 Dec 2012, Paul Heckbert wrote:

I have a test program that uses libtiff to create an EXIF IFD, and I found that with libtiff version 4.0.3, the TIFFTAG_EXIFIFD tag was being written with TIFFDataType TIFF_IFD into Classic TIFF files (TIFF files that are not BigTIFF). Unfortunately, TIFF_IFD=13 is a new type and is not yet standard. Much existing software expects the EXIFIFD tag to have type TIFF_LONG=4 and will not read the EXIF tags if the type is written as TIFF_IFD. This means that writing of EXIF tags is not working as broadly as possible with libtiff version 4.0.3.

This is all very interesting. If TIFF_LONG is used, what should we do while writing BigTIFF format? Should TIFF_LONG only be used for Classic TIFF?