[gdal-dev] Computing my overviews for GeoTIFF

[Javier Jimenez Shaw]

Sounds good.

My next question is how to write the overviews data efficiently.
I see that there is a method "GDALRasterBand * GDALRasterBand::GetOverview
( int i ) ", but for that I need to deinterlace the image (copying it), and
call it 4 times. Is there any trick I am missing while calling
GDALRasterBand::RasterIO? Maybe some black magic with the pixel and line
spaces? The images/overviews I get from the GPU are interlaced (RGBARGBA)
On the other side there is "GDALDataset::RasterIO(...)", but there is not
explicit way to set the overview level.

Thanks
.___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
Entre dos pensamientos racionales
hay infinitos pensamientos irracionales.



On Tue, 13 Jul 2021 at 14:04, Even Rouault <even.rouault at spatialys.com>
wrote:

> Javier,
>
> You can use the "NONE" resampling method in BuildOverviews() or gdaladdo
> to create the overviews IFD without allocating any storage, and then you
> can open the file in update mode to set whatever values you want.
> APPEND_SUBDATASET=YES will not set the appropriate value for the
> SubFileType TIFF tag, and thus such pages won't be recognized as overviews
>
> Even
> Le 13/07/2021 à 13:57, Javier Jimenez Shaw a écrit :
>
> Hi
>
> I am computing the overviews of a GeoTIFF on my own (using the GPU, much
> faster), and I want to include them in the tif file (also in the ovr
> sidecar file).
> What is the best way to do it? Just creating a multipage TIFF (I guess
> with the option APPEND_SUBDATASET=YES)? Is there anything else needed
> (metadata, tiff tags, etc)?
>
> So far I want to do it in RGBA 8 bit images. (In the future I want to do
> it also in float32 images with nodata value and any number of bands, but no
> hurry).
>
> I am using GDAL 3.3.1
>
> Any help is welcome.
>
> Thanks.
> Javier.
> .___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
> Entre dos pensamientos racionales
> hay infinitos pensamientos irracionales.
>
>
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