[gdal-dev] Fwd: GeoPKG Zoom Level Calculation

[Even Rouault]

On jeudi 14 septembre 2017 06:26:40 CEST Roarke Gaskill wrote:
> Even,
> 
> Thanks for your reply.  I get it now.  :)
> 
> I am new to gdal in general.  For context, why does CreateCopy() choose the
> nearest zoom level and not SetGeoTransform()?  

Most drivers don't handle directly this concept of predefined tiling schemes, and if you want 
to apply one, you need to use gdalwarp and setting correctly the extent, resolution, etc... The 
CreateCopy() implementation in the GPKG driver, when tiling scheme is specified, does that 
automatically for you.

But if you do SetGeoTransform() manually and then use the RasterIO() API, no resampling 
can occur at that level of the driver (like any other drivers), so you have to specify a 
resolution that respect the constraints of the tiling scheme.

> As a new user, it seems to
> me the ZOOM_LEVEL_STRATEGY should apply to both the SetGeoTransform() and
> CreateCopy().

I've just added a precision in the doc to mention that ZOOM_LEVEL_STRATEGY only applies 
to CreateCopy()

Even

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