[gdal-dev] .ovr files and Lanczos

[Even Rouault]

Le mardi 29 novembre 2011 18:42:27, Eli Adam a écrit :
> Are .ovr files just tifs with a different file extension?
> 
> If so, could you use, gdalwarp -tr # # -r lanczos output.ovr?

Yes, basically .ovr files are just tifs file (actually, I believe it could be 
any raster type recognized by GDAL). There can have some special metadata for 
particular cases like building overviews of 1-bit imagery (black&white), where 
the result of the overview is 8-bit grey level to be nice-looking. But that's 
all.

However note that generally the resampling algorithm of gdalwarp have not been 
coded to be applied to subsampling (they are adapted to reprojection where the 
number of pixels isn't dramatically changed by the operation). So depending on 
which one is used, the result might not be satisfactory.