On Mon, Feb 21, 2011 at 2:26 PM, Jay Jennings <jennings....@geoeye.com> wrote: > [...] I’m looking for a > downsampling scheme that creates a result pixel by averaging all relevant > source pixels (I know, for 32:1 downsample, that means 1024 source pixels > for each result pixel !) with the hope of an output that is not “speckled” > or “grainy” insofar as possible.
gdalwarp would probably give you the most control over the resampling algorithm: http://www.gdal.org/gdalwarp.html Look particularly at the -tr (target resolution, in georeferenced units) or -ts (target size, in pixels) options. For example, to produce a 32:1 thumbnail of a 44418x39108 GeoTIFF that I have laying around, $ gdalwarp -ts 1389 1223 -r bilinear input.tif output.tif You can experiment with the different resampling algorithms to find one you like (near, bilinear, cubic, cubicspline, lanczos). > gdaladdo -r average -ro XXXXX.tif 32 > > But that produces a surprising error message, namely: > > ERROR 4: `XXXXX.tif.ovr' does not exist in the file system, and is not > recognised as a supported dataset name. I tried gdaladdo with your arguments on the GeoTIFF I mentioned above (which is 3.4 GB) and it executed with no problems. Your error sounds like the *.tif.ovr file simply didn't get created; you might double-check that you have write permissions in the directory where your input file lives. I believe overviews are always written into the same directory as their source file, rather than your current working directory. -b -- Brian Claywell bcclayw...@gmail.com _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
