Radim Blazek-2 wrote > > > QGIS is using GDALRasterIO() which reads a single pixel on original > resolution. AFAIK, ECW is using tiles internally so it should be all > very fast. I can imagine 2 problems: > > - the tiles in ECW file are too big - can you verify somehow how big > are the tiles? > > Hi Radim, I'm not ecw specialist, but I understand it is a wavelet compression algorithm, not a tiled one. There is one big image with pyramids inside.
Radim Blazek-2 wrote > > - GDAL is reading bigger portion of data than necessary (cc to GDAL list) > > Is it drawing of the raster also so slow (on raster resolution zoom)? > > Radim > > No everything is fine when drawing data, whatever resolution I use, this is the big thing with ecw. I must say I find that it was a bit faster with 1.7.4 than 1.8 and later. But this could be related to other factors like internal network capacities.. I haven't benched on it yet. -- View this message in context: http://osgeo-org.1560.n6.nabble.com/Large-raster-ecw-identify-very-long-tp4996953p4996972.html Sent from the Quantum GIS - Developer mailing list archive at Nabble.com. _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer