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TIFF and LibTiff Mail List Archive

Thread

2007.01.31 10:53 "[Tiff] Interpreting SubIFDs tag", by mikk
2007.01.31 17:23 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.02.01 09:42 "Re: [Tiff] Interpreting SubIFDs tag", by Gerben Vos
2007.02.01 18:32 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.01.31 19:24 "Re: [Tiff] Interpreting SubIFDs tag", by Phil Harvey
2007.01.31 19:54 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.01.31 22:24 "RE: [Tiff] Interpreting SubIFDs tag", by Grissom, Ed
2007.02.01 18:17 "RE: [Tiff] Interpreting SubIFDs tag", by Phil Harvey
2007.02.01 18:34 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.02.01 18:48 "Re: [Tiff] Interpreting SubIFDs tag", by Phil Harvey
2007.02.01 19:00 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.02.01 19:36 "Re: [Tiff] Interpreting SubIFDs tag", by Phil Harvey
2007.02.01 20:02 "Re: [Tiff] Interpreting SubIFDs tag", by Joris
2007.02.01 15:46 "Re: [Tiff] Interpreting SubIFDs tag", by Phil Harvey

2007.01.31 22:24 "RE: [Tiff] Interpreting SubIFDs tag", by Grissom, Ed

TIFFers

Here is the document that invented the SubIFD concept -- this is the "Tiff Trees" approach. (http://partners.adobe.com/public/developer/en/tiff/TIFFPM6.pdf)

It clearly states in the final paragraph that each SubIFD value is to be considered a pointer to the first IFD in a list of IFDs.

Consider that instead of a single thumbnail, you might have a full set of reduced resolution versions of the main image. This is typically used for LARGE raster files to provide fast zooming capabilities.

--
ed grissom
ed.grissom@intergraph.com

-----Original Message-----

From: tiff-bounces@lists.maptools.org [mailto:tiff-bounces@lists.maptools.org] On Behalf Of mikk

I'm a bit confused with interpreting SubIFDs tag value.

Each value of N values in SubIFDs tag is an offset (from the beginning of the TIFF file, as always) to a child IFD. But is each value of N values an offset to a single child IFD, or to the first IFD from a linked list of IFDs? When I read each of these N child IFDs, am I supposed to interpret NextIFDOffset field and read next directory from this position for each of child IFDs?

Could anyone put some light on this, please?

Thanks in advance, kind regards,