[Qgis-developer] Re: [gdal-dev] GDALWarpOperation.ChunkAndWarpImage slow on large tiffs

[Radim Blazek]

Hi,
yes that is the mail reporting the error.

Thank you for explanation. I see that I have to reintroduce all the
staff for GDALRasterIO()

Radim

On Wed, Mar 9, 2011 at 8:50 PM, Even Rouault
<even.rouault at mines-paris.org> wrote:
> 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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>