[gdal-dev] Interpolation when using the WMS format

[Peter Hopfgartner]

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

As can be clearly seen, the labels are hard to read.

Reagrds,

Peter

-- 
Peter Hopfgartner
R3 GIS
web  : www.r3-gis.com

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