[gdal-dev] /vsisubfile/ and using MrSID SDK for JPEG2000 in NITF
Frank Warmerdam
warmerdam at pobox.com
Wed Jan 14 02:10:51 EST 2009
Folks,
I have implemented a new VSI driver allowing subregions of any file to
be treated as a file object. The syntax is:
/vsisubfile/<offset>_<size>,<filename>
So, for instance, to read a jpeg2000 datastream in a file named /data/abc.ntf
with the data stream starting at byte 1000 and being 5000 bytes long you would
use:
/vsisubfile/1000_5000,/data/abc.ntf
The primary goal of this was allowing the JP2MrSID driver to be used to read
jpeg2000 data from NITF files. To that end I have modified the NITF driver
in trunk to use this syntax instead of the J2K_SUBFILE: syntax that was
used previously, and depended on special handling in each jpeg2000 driver.
I also discovered a couple quirks in the mrsid driver - in particular
with the custom stream implementation that had been making it's use fail
in some cases with the v7 MrSID SDK. I have corrected those.
It is now possible, in trunk, to read jpeg2000 nitf files with the MrSID
driver.
I have not yet confirmed the ECW and JP2KAK drivers are still working
properly in this situation, but they ought to be since both supported
VSI*L file streams.
Best regards,
--
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush | Geospatial Programmer for Rent
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