[gdal-dev] RasterIO antialiased subsampling

Tamas Szekeres szekerest at gmail.com
Wed Sep 23 16:31:11 EDT 2009


I'm not quite sure whether this issue have already been raised or not, but
I'd be interested in having on-the fly antialiasing support when the raster
is subsampled within a RasterIO operation.
I'm just trying to display OpenStreetMap rasters provided by the GDAL TMS
mini driver in MapServer but the images are looking quite raspy at certain
scales (see   http://vbkto.dyndns.org:1280/tests/sample.png ), and it may be
dedicated to how the image is subsampled (kinda like a simple nearest
neighbour is used) during a RasterIO operation in GDAL.

I've took a look at the code, but I see no option to use more sophisticated
algorithms when composing the destination image, like those provided by the
gdal warp API (ReprojectImage) in effect. Additionally, I can see an
'antialias' option implemented by the gdal2tiles script, which came from an
external library and missing from the set of the built in resampling
algorithms of the GDAL library.

Let me know if anyone have already been coming to face with such a problem
or have further ideas, or workarounds.

Best regards,

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