[gdal-dev] GDALWarpOperation.ChunkAndWarpImage slow on large tiffs

[Even Rouault]

Le mercredi 09 mars 2011 19:46:26, Radim Blazek a écrit :
> Hi,
> 

Skimming qgis mailing list, I read this http://lists.osgeo.org/pipermail/qgis-
developer/2011-March/013291.html

Was it the report you were refering too ? If yes, then the report gives an 
interesting hint. You must be aware that the warping code does not take 
advantage of overviews (it is intended to operate on the full-resolution 
raster, and not for downsampling as Frank underlined), so you will have really 
bad performance comparing too GDALRasterIO() if the output dimensions are much 
smaller than the input window size.

> GDALWarpOperation.ChunkAndWarpImage was reported to be extremly slow
> on larger geotiff (over 1GB). Is it possible that it is much slower
> with respect to GDALRasterIO()  even without reprojection? Should I
> return to 'manualy' reading data via GDALRasterIO() + fidling with
> data extents and cells alignement? I thought that GDAL
> ChunkAndWarpImage will do it even faster, possibly knowing better (?)
> various formats nature.
> 
> Is there way to tune somehow performance? Currently no reprojection
> and GRA_NearestNeighbour.
> 
> Still the same code which I posted before
> http://trac.osgeo.org/qgis/browser/trunk/qgis/src/providers/gdal/qgsgdalpro
> vider.cpp?rev=15400#L625
> 
> Thanks for help.
> Radim
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