LibTiff Mailing List

Mark,

Mark Pilon wrote:
> I still need to handle the problem image - is there some way to
> implement a 'null' codec to get me the image data so that I can go
> off to the side and decompress it line-by-line?
>
> or do I even need to implement anything? -- could I just rewrite the
> compression type for this image as 'none' ?

If I understand correctly that you seek access to the compressed
strip/tile data, without LibTiff expanding any of it to a complete
uncompressed strip/tile, then I think TIFFReadRawStrip and
TIFFReadRawTile may be useful. See
http://www.remotesensing.org/libtiff/man/TIFFReadRawStrip.3tiff.html and
http://www.remotesensing.org/libtiff/man/TIFFReadRawTile.3tiff.html.

Of course, using this method, you'll still have allocated memory of a
complete compressed strip/tile. Seems like little gain from the
substantial effort of writing your own more streaming decompressors to
handle the data 'off to the side'.

If you want the offsets/bytecounts of the strips/tiles, so that you can
read smaller buffers, feeding it through your custom decompressors a
small buffer at the time, and thus further streamlining the process for
minimum memory requirements, you could simply use TIFFGetField on the
StripOffsets/StripByteCounts/TileOffsets/TileByteCounts tags. For exact
datatypes and stuff, see
http://www.remotesensing.org/libtiff/man/TIFFGetField.3tiff.html. For
more details on the tags themselves, search over at
http://www.awaresystems.be/imaging/tiff/tifftags.html.

Or am I misunderstanding your need?

Joris Van Damme
info@awaresystems.be
http://www.awaresystems.be/
Download your free TIFF tag viewer for windows here:
http://www.awaresystems.be/imaging/tiff/astifftagviewer.html


AWARE [SYSTEMS]		Imaging expertise for the Delphi developer
		TIFF and LibTiff Mailing List Archive
	LibTiff Mailing List TIFF and LibTiff Mailing List Archive September 2005 Previous Thread Next Thread Previous by Thread Next by Thread Previous by Date Next by Date Contact The TIFF Mailing List Homepage This list is run by Frank Warmerdam Archive maintained by AWare Systems	Thread 2005.09.12 21:22 "read-by-scan-line buffers full strip, part 2", by Mark Pilon 2005.09.13 01:26 "Re: read-by-scan-line buffers full strip, part 2", by Joris Van Damme 2005.09.13 15:34 "Re: read-by-scan-line buffers full strip, part 2", by Mark R Olin 2005.09.13 15:58 "Re: read-by-scan-line buffers full strip, part 2", by Joris Van Damme 2005.09.13 16:17 "read-by-scan-line buffers full strip, part 3", by Mark Pilon 2005.09.13 16:54 "Re: read-by-scan-line buffers full strip, part 3", by Joris Van Damme 2005.09.13 17:48 "Re: read-by-scan-line buffers full strip, part 3", by Mark Pilon 2005.09.13 01:26 "Re: read-by-scan-line buffers full strip, part 2", by Joris Van Damme Mark, Mark Pilon wrote: > I still need to handle the problem image - is there some way to > implement a 'null' codec to get me the image data so that I can go > off to the side and decompress it line-by-line? > > or do I even need to implement anything? -- could I just rewrite the > compression type for this image as 'none' ? If I understand correctly that you seek access to the compressed strip/tile data, without LibTiff expanding any of it to a complete uncompressed strip/tile, then I think TIFFReadRawStrip and TIFFReadRawTile may be useful. See http://www.remotesensing.org/libtiff/man/TIFFReadRawStrip.3tiff.html and http://www.remotesensing.org/libtiff/man/TIFFReadRawTile.3tiff.html. Of course, using this method, you'll still have allocated memory of a complete compressed strip/tile. Seems like little gain from the substantial effort of writing your own more streaming decompressors to handle the data 'off to the side'. If you want the offsets/bytecounts of the strips/tiles, so that you can read smaller buffers, feeding it through your custom decompressors a small buffer at the time, and thus further streamlining the process for minimum memory requirements, you could simply use TIFFGetField on the StripOffsets/StripByteCounts/TileOffsets/TileByteCounts tags. For exact datatypes and stuff, see http://www.remotesensing.org/libtiff/man/TIFFGetField.3tiff.html. For more details on the tags themselves, search over at http://www.awaresystems.be/imaging/tiff/tifftags.html. Or am I misunderstanding your need? Joris Van Damme info@awaresystems.be http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html

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2005.09.13 01:26 "Re: read-by-scan-line buffers full strip, part 2", by Joris Van Damme