[gdal-dev] Default progression order in JP2OpenJPEG driver

[Even Rouault]

> 
> OpenJPEG begins to be fast enough for practical use with tiled JPEG2000.
> Unfortunately it is almost unusable with single tile images like the ones
> in the directory below. Images are open data, only attribution required:
> National Land Survey of Finland, 2014.
> 
> http://kartat.kapsi.fi/files/orto/etrs-tm35fin/mavi_vv_25000_50/2014/M52/10
> m/1/
> 
> Let's hope that OpenJPEG developers will discover some day how to read
> single-tile images at reasonable speed.

Yes that sums up to have opj_set_decode_area()+opj_decode() work efficiently. 
Currently GDAL uses that API if there's a single-tile. Otherwise it uses the 
opj_get_decoded_tile() API to decode tile per tile.

This should be better discussed on their channel ( 
https://groups.google.com/forum/#!forum/openjpeg ).


> Now I cannot imagine that I would
> use OpenJPEG driver even for converting such images with gdal_translate.
> There is a free-as-in-beer solution by using JP2ECW read-only driver for
> JPEG2000->GeoTIFF conversion followed by use of JP2OpenJPEG driver for
> GeoTIFF->tiled JPEG2000 but that does not make my open source minded soul
> happy.

Yes, and that causes further quality loss.

> 
> -Jukka Rahkonen-
> 
> 
> 
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