On Tuesday, October 13, 2015 11:25:47 Even Rouault wrote: > Salut Yves, > > > * is it possible to choose the driver used by gdal? For instance, in my > > second test, my gdal install have two driver; ECW SDK and OpenJpeg. > > Currently, I am building several gdal instance to test each driver :/ > > Yes, see https://trac.osgeo.org/gdal/wiki/ConfigOptions#GDAL_SKIP > > For example if you want to exclude the JPEG2000 and JP2OpenJPEG drivers and > only use JP2ECW: > > GDAL_SKIP="JPEG2000,JP2OpenJPEG" gdalinfo foo.jp2
Exactly what I need, I should read this page one of this day because I know that it exists but never read it :) > > * the difference between the two test, is it a problem from the driver > > used > > of from gdal release? > > It is (mainly) a problem of the underlying library. > The JPEG2000 driver uses the jasper library which needs to decompress the > whole imagine into memory. For some reason due to how jasper works, to get > the infos displayed by gdalinfo, we also need to decompress the imagery. > Could perhaps be made smarter, but as soon as you would need to query the > value of a single pixel, the whole image would be uncompressed, so... > Other JPEG2000 drivers (and underlying libraries) are smarter and will only > decompress(*) the requested area (and nothing for just a simple gdalinfo). > > Even > > (*) in the case of JP2OpenJPEG, this is only true if the JPEG2000 image is > tiled. If it is made of a single tile, requesting just a few pixels will be > slow (but will not need a lot of RAM as far as I remember) Interesting, so my thought to try with openjpg2000 is correct. Thanks Even! Y. _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev