[Gdal-dev] Re: JP2 files (JPEG2000)

[Jukka Rahkonen]

Frank Warmerdam <warmerdam <at> pobox.com> writes:
> juan wrote:
> > Dear all,
> > 
> > I have to read some JP2 geocoded image files that have
 been created with Kakadu 
> > software (I believe). The thing is that using gdal drivers
 as in the tutorial 
> > but I see the file, dimensions of the image and type but I seem to 
loose the 
> > geo-referencing information and also when I try to
 access the values they all 
> > return a zero value. 
> > 
> > Does anyone tell me if GDAL supports this type of files?
 If not, does anyone 
> > know a solution to read these files?
> 
> Juan,
> 
> GDAL supports a variety of geocoding formats in JPEG2000 files, but I'm not
> sure what mechanism Kakadu is using for it's encoding.  I'd add that some
> of the support for different formats was added fairly recently to GDAL
> so if you are using something older than 1.4.0 that could be an issue.
...

Hi,

Kakadu is after all C++ library for those who would like to make
own jpeg2000 applications.  It does include some extremely
good demonstration programs that can be used for compressing,
decompressing, viewing and serving jpeg2000 imagery. The problem
is that the main aim of the Kakadu developers is not to improve
these demo programs, while people like me are willing to use those
as they are because they are full of features, fast, and free of
charge for non-commercial use.
When it comes to geo-referencing, kdu_compress can compress tiff
files directly to jpeg2000. It they are GeoTiffs then the
georeferencing is transferred as well with GeoJP2 system, and
GDAL will recognise it.  With kdu_compress you can only compress
from Windows BMP, PGM/PPM (portable gray map/ portable pixel map,
or RAW formats (you can demonstrate quite a lot of jpeg2000 stuff
with those formats).
So the only way to include georeferencing to jpeg2000 files made
with kdu_compress is to start from GeoTiff files and compress them.
By now it is better to have pixel interleaved geoTIFF to start
from (creation option INTERLEAVE=PIXEL in GDAL), because the 
downloadable demo executables may not handle band interleaved
images correctly.  I've been told that this is corrected in the
next demo release, and it is already correected in the SDK.
Another alternative is to use worldfile, I remember that GDAL
accepts world files named either as .j2w or .wld.

-Jukka Rahkonen-