[gdal-dev] slow translate with OVERVIEW_LEVEL=NONE when no overviews exist

[Michael Sumner]

When I translate this GeoTIFF to 10% original size, it's very very slow if
OVERVIEW_LEVEL=NONE is set.

The GeoTIFF has no overviews.

export dsn="/vsicurl/
https://github.com/mdsumner/cog-example/raw/main/cog/sentinel-image.tif"
## takes *forever*
gdal_translate $dsn  out.tif -outsize 219 226 -oo OVERVIEW_LEVEL=NONE

## works fast as expected
gdal_translate $dsn  out.tif -outsize 219 226

I found this in a package that has a global open option setting for
overviews for subsampling with RasterIO(). There we could detect that
overviews are not present, or even just not set it at all ... (better to
use GDALwarp() for general cases IMO).

But, is there a good reason why setting that open option affects translate
for sources with no overviews?

I'm in master at ebac6b74a429fa6eeeb94edd074b6cb60072a35f

Cheers, Mike



-- 
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com
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