[Gdal-dev] Problem for build overviews
mateusz at loskot.net
Tue Jan 9 06:31:17 EST 2007
mouhamad mbaye wrote:
> When i replace GA_ReadOnly with GA_Update
> i have this error
> Une exception non gérée du type 'System.ApplicationException' s'est
> produite dans gdal_gdal_csharp.dll
> Informations supplémentaires : The JPEG driver does not support update
> access to existing datasets.
I missed the detail explained in JPEG driver docs.
GDAL doesn't support embedded overviews for JPEG format.
For JPEG format you can only build overviews in external .ovr file:
This is automatically handled by GDALDataset::BuildOverviews() for
JPEG driver. You can see apps/gdaladdo.cpp sources to see how it's
build. Also, using gdaladdo utility should be good for testing.
Note, .ovr files creation is a default method for drivers which do not
support embedded overviews natively.
If you're playing with JPEG2000, check note at the bottom of this page:
p.s. Thanks to Andrey for teaching me about overviews support :-)
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