2009.02.17 08:12 "Re: [Tiff] DNG question", by

Gordon,

There is some sample code for a simple c DNG exporter (elphel_dng.c), which uses different TIFF

directories to store the thumbnail and the raw data. Unfortunately, my DNG files only have a single TIFF directory when I open them. I can extract the RAW data with dcraw, but the code is somewhat cryptic, so I don't quite understand how to access it. Since I use the Adobe DNG converter to create the files from various different SLR cameras, I can just set the compression to none, so that shouldn't be a problem.

You've two challenges facing you. The first is discovering the IFD structure and the location of what you're looking for, the second is accessing the data you're after. LibTiff might not be too helpfull. Its support for SubIFDs, probably improved in recent versions, might still be somewhat cryptic I guess.

If you send me some DNG files, to my private e-mail address, maybe I can help out by sending you a complete overview of all IFDs in those files. My tools are based on my proprietary TIFF codec, and support the complete IFD tree structure fine. That might at least reveal where the stuff is that you're after.

Don't send the DNG files to the list, though, the list rightly does not accept long attachements.

Best regards,

Joris