[gdal-dev] Overviews using GDAL

[Dmitry Baryshnikov]

Hi,

GDALDataset::RasterIO pass the  request off to each band objects 
rasterio methods with appropriate arguments
In  GDALRasterBand::RasterIO 
(http://www.gdal.org/classGDALRasterBand.html#a5497e8d29e743ee9177202cb3f61c3c7)

"Some formats may efficiently implement decimation into a buffer by 
reading from lower resolution overview images."

So you don't need to choose the right overview level by yourself. 
Usually it selected automatically. You can inspect GDAL sources for how 
it chosen. GDAL don't have the special function to find out which 
overview level is chosen.

Best regards,
     Dmitry

14.12.2012 11:24, HariPrasad ?????:
> Thanks Dmitry  for your replay.
>
> I did that using IRasterIO(), but non of the IRasterIO() parameters has
> which overview its displaying. (i.e overview number). How can i know which
> overview it has displayed?
>
> I used GetOverview(int). I was able to get the overview numbers. But when i
> zoomed to maximum the base image has to be displayed instead of overview if
> i am not wrong, which i am not getting the base image number.
>
> am iam thinking in right direction?
>
>
>
> --
> View this message in context: http://osgeo-org.1560.n6.nabble.com/Overviews-using-GDAL-tp5022226p5022926.html
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