[Gdal-dev] Problem building overviews

[Frank Warmerdam]

On Thu, 3 Mar 2005 16:01:04 -0500, William Lyons
<wlyons at prologic-inc.com> wrote:
> I'm attempting to build overviews for a dataset containing a single band
> with a color interp of palette index (a CADRG file) 
> 
> When I use the AVERAGE option the map looks bad when scaled down beyond a
> certain point. 

William, 

In general paletted files should not be averaged for overviews. 
 
> But when I use the MODE option I get the following errors: 

MODE is not actually implemented as a downsampling type.  I 
should either remove it from the Usage message, or implement it. 
However, I can never decide which to do.

> ERROR 5: Access window out of range in RasterIO().  Requested 
> 
> (0,768) of size 768x1 on raster of 768x768. 
...
> I'm using a pretty old CVS snapshot.  So, my apologies if this has already
> been addressed. 

Hmm, the above are not expected.  I would encourage you to try 
"-r near" with current code (perhaps the beta) and see if the problem
still occurs.  If so, report it with details and I wll see what I can do. 

If you are using the CADRG data directly from OGDI and trying to build
overviews against an OGDI datasource, you might be well advised 
convert to GeoTIFF first. 

Best regards,
-- 
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