[gdal-dev] Downsample with averaging?

[Chaitanya kumar CH]

Jay,

Can you provide a sample file that gives this error?

On Tue, Feb 22, 2011 at 1:56 AM, Jay Jennings <Jennings.Jay at geoeye.com>wrote:

> Hello list,
>
> (using GDAL 1.8.0) I am trying to create a 32:1 down-sampled overview of a
> GeoTiff satellite image.  My first thought was gdal_translate, with args
> such as “-outsize 3.125% 3.125%”… which produces surprisingly high quality
> given the absence of a resampling option.   However 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.
>
>
>
> I also looked at gdaladdo, which does have the “-r average” resampling
> option… the guidance at gdal.org seems to suggest that it can produce a
> 32:1 GeoTIFF external overview with a command like this:
>
>
>
> 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.
>
>
>
> Am I barking up the wrong tree with gdaladdo for this purpose ?  Anybody
> have any suggestions for highest-quality down-sampling ? Thanks in advance.
>
>
>
> --Jay Jennings
>
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>



-- 
Best regards,
Chaitanya kumar CH.
/tʃaɪθənjə/ /kʊmɑr/
+91-9494447584
17.2416N 80.1426E
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