Salut Evan, thanks for you recipe. Unfortunately, what I am really interested in is to use this from MapServer. Could you give me a pointer in the source where the resampling takes place?
Thanks, Peter Am 18.09.2014 um 22:11 schrieb Even Rouault <even.roua...@spatialys.com>: > Le jeudi 18 septembre 2014 17:40:11, Peter Hopfgartner a écrit : >> Hi, everybody >> >> we are using the GDAL WMS driver for getting maps from a public WMTS >> service, http://www.basemap.at. Anyway, the resulting image does not >> look smooth. In particular, I would guess that the the image was scaled >> with something like a nearest neighbor algorithm. >> So my question is simply, if I can switch the interpolation method in >> some place. >> >> The XML file, taken from >> http://gisforge.wordpress.com/2012/11/06/basemap-at-wmts-layer-in-qgis/, >> is: >> >> <GDAL_WMS> >> <Service name="TMS"> >> <ServerUrl>http://maps.wien.gv.at/basemap/geolandbasemap/normal/google3857/ >> ${z}/${y}/${x}.jpeg</ServerUrl> </Service> >> <DataWindow> >> <UpperLeftX>-20037508.34</UpperLeftX> >> <UpperLeftY>20037508.34</UpperLeftY> >> <LowerRightX>20037508.34</LowerRightX> >> <LowerRightY>-20037508.34</LowerRightY> >> <TileLevel>18</TileLevel> >> <TileCountX>1</TileCountX> >> <TileCountY>1</TileCountY> >> <YOrigin>top</YOrigin> >> </DataWindow> >> <Projection>EPSG:3857</Projection> >> <BlockSizeX>256</BlockSizeX> >> <BlockSizeY>256</BlockSizeY> >> <BandsCount>3</BandsCount> >> <Cache /> >> </GDAL_WMS> >> >> The command is: >> >> gdal_translate -srcwin 35500000 23500000 100000 100000 -of JPEG -outsize >> 250 250 basemap_at.xml basemap_at.jpg > > Peter, > > Resampling done by gdal_translate is nearest neighbour, so not always that > great. > > What you can do is select an outsize that is compatible with the source > overviews. In TMS, the ratio between sucessive overviews work with factor of > 2, so you should select an outsize of 10000 / 2^N. The closest is 10000 / 256 > = 390.625 -> 391 > > So > > gdal_translate -srcwin 35500000 23500000 100000 100000 -outsize > 391 391 basemap_at.xml tmp.tif > > and then: > > gdalwarp tmp.tif tmp2.tif -r lanczos -ts 250 250 (you can try different > resampling kernel) > gdal_translate tmp2.tif basemap_at.jpg -of JPEG > > Best regards, > > Even > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
