[gdal-dev] /vsisubfile/ and using MrSID SDK for JPEG2000 in NITF

[Frank Warmerdam]

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,
-- 
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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