[gdal-dev] Creating multiple zooms in MBTiles generation

[Even Rouault]

Le vendredi 13 mai 2016 14:24:38, Gane R a écrit :
> Hi,
> 
> I was working with gdal 2.1.0, I was trying to convert a geopackage raster
> to mbtiles, I used GDALCreateCopy to convert the dataset to mbtiles.
> 
> On http://www.gdal.org/frmt_mbtiles.html
> 
> I saw an example to use gdal_translate and then to use gdaladdo to
> overviews
> 
> Q1: I got only one level of zoom level in the mbtiles. Is there any
> creation option to say to generate mbtiles from a to b zooms ?
No. Creation options for MBTILES are documented there : 
http://gdal.org/frmt_mbtiles.html
> or I have to
> do by build overviews ???
Yes
> 
> 
> Q2: I tried to convert the Geopackage ERDC_Whitehorse_GeoPackage.gpkg size
> 111 MB in Web Mercator EPSG:3857 from the url
> 
> http://www.geopackage.org/#sampledata
> 
> (GeoPackage contains a raster tile pyramid that was created with free
> imagery obtained from Geomatics Yukon and covers an approximately 30
> square-kilometer area centered on the City of Whitehorse. It uses the Web
> Mercator (EPSG:3857) coordinate reference system, 256x256 pixel tiles,
> contains zoom levels 11-18, and is 110.8MB in size)
> 
> 
> 
> *The resulting mbtiles was to 621MB Is this due to default PNG zlevel
> settings or any thing can be done on this ?*

The original GPKG probably uses JPEG compression, so if you use -co 
TILE_FORMAT=JPEG you should get to a similar size.  But this will cause some 
quality loss due to decompression/recompression done in GDAL.

You can in a few commands convert a GPKG to MBTiles, provides that it uses a 
Google Mercator tiling scheme as the sample dataset you use seem to be.
Have a look at the procedure described at the end of 
http://erouault.blogspot.fr/2014/12/gdal-geopackage-raster-support.html

Even

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