[gdal-dev] Do RasterIO of VRT format using arbitrary overviews of origin files

[Even Rouault]

On vendredi 2 février 2018 11:28:08 CET Zi Chui wrote:
> Hello,
> 
> I have some jpeg2000 files, and i know this format support arbitrary
> overviews,
> GdalRasterBand::RasterIO will automatically use it in downsampling mode.
> 
> But i noticed that the vrt file generated by those jp2 files do not
> has arbitrary
> overviews (GdalRasterBand::HasArbitraryOverviews return FALSE).
> 
> So here goes my question, dose GdalRasterBand::RasterIO of VRT format still
> using arbitrary overviews of origin files?

Yes, even if the VRT driver doesn't expose all capabilities of underlying sources, it is able to 
do efficient dowsampling if the sources support it.

Even

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