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November 2012

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2012.11.24 00:09 "help writing thumbnails to TIFF file?", by Paul Heckbert
2012.11.24 00:46 "Re: help writing thumbnails to TIFF file?", by Joris Van Damme
2012.11.25 13:01 "Re: help writing thumbnails to TIFF file?", by Edward Lam
2012.11.25 15:08 "Re: help writing thumbnails to TIFF file?", by Joris Van Damme
2012.11.27 02:10 "Re: help writing thumbnails to TIFF file?", by Paul Heckbert
2012.11.27 03:25 "Re: help writing thumbnails to TIFF file?", by Bob Friesenhahn
2012.11.27 13:12 "Re: help writing thumbnails to TIFF file?", by Joris Van Damme
2012.11.27 14:38 "Re: help writing thumbnails to TIFF file?", by Olivier Paquet
2012.11.28 03:06 "Re: help writing thumbnails to TIFF file?", by Olivier Paquet
2012.12.08 04:35 "Re: help writing thumbnails to TIFF file?", by Paul Heckbert
2012.11.27 18:09 "Re: help writing thumbnails to TIFF file?", by Daniel Mccoy

2012.11.27 14:38 "Re: help writing thumbnails to TIFF file?", by Olivier Paquet

On Mon, Nov 26, 2012 at 9:10 PM, Paul Heckbert <ph@cs.cmu.edu> wrote:
> I side with those that are saying that TIFFCheckpointDirectory is
> useful and (at least sometimes) works properly.  Without
> TIFFCheckpointDirectory, the directory would always appear at the end
> of a TIFF file, after the pixels, and reading partial TIFF files would
> be impossible.  Some control of data order in the file IS useful,
> namely: does the directory appear before or after the pixels?

Ok, this isn't that relevant but I'll try to clear up some confusion.

Reading a partial TIFF does not require that the directory come before
the pixels. It just happens to be a sensible place to put it which
avoids gaps in the file and works as long as the directory does not
change size. Note here that by "partial" TIFF I mean a TIFF which the
software is not finished generating (what the function was originally
written for), not a full TIFF file from which you only have the first
N bytes (what you want).

> My current hypothesis: TIFFCheckpointDirectory works fine if you're
> writing only one directory, but it's buggy when there are multiple
> directories.

Quite possible. It works by keeping the directory in memory for
further checkpoints or the final write. Getting it to work with
multiple directories requires rereading them (with TIFFSetDirectory)
which is very different. It does look like it should work so it can't
be that far from actually working. I will try to find some time to
take a closer look.

Olivier