[gdal-dev] BuildOverviews

[Frank Warmerdam]

Pierre Grout wrote:
> 
> Hi all,
> 
> I would like to know how to use the Dataset's Method : BuildOverviews.
> 
> I don't know what to set for :
> - panOverviewList

List of overview reduction factors. For instance {2, 4, 8} on a base image
of 1024x1024 would give a 512x512, 256x256 and 128x128 overview. 

> - pfnProgress
> - pProgressData

I have added documentation this morning. See GDALDummyProgress() on the
gdal.h page:

http://www.remotesensing.org/gdal/gdal.h.html

> My aim is to use it for making small image of the main one. (~10 x
> smaller ).

You should be able to pass panOverviewList={10} to get a 10x10 reduction.
Do you want this to be a separate file, or do you just want it for
accelerated loads with RasterIO()? 

> Wich format does support to build such Overviews inside.(I know TIFF
> can, but others ? )

The SAR_CEOS, CEOS, JPEG, PNG, EFF, ESRI BIL, MFF, and PCI .aux formats 
currently support external overviews (build in a .ovr file).

Keep the questions coming, and I will try to update the documentation as
things come up. 

Best regards,

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