AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2005.09.12 21:22 "[Tiff] read-by-scan-line buffers full strip, part 2", by Mark Pilon
2005.09.13 01:26 "Re: [Tiff] read-by-scan-line buffers full strip, part 2", by Joris Van Damme
2005.09.13 15:34 "RE: [Tiff] read-by-scan-line buffers full strip, part 2", by Mark R. Olin
2005.09.13 15:58 "Re: [Tiff] read-by-scan-line buffers full strip, part 2", by Joris Van Damme
2005.09.13 17:48 "Re: [Tiff] read-by-scan-line buffers full strip, part 3", by Mark Pilon
2005.09.13 16:17 "[Tiff] read-by-scan-line buffers full strip, part 3", by Mark Pilon
2005.09.13 16:54 "Re: [Tiff] read-by-scan-line buffers full strip, part 3", by Joris Van Damme

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

Mark,

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/
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