Le 13/07/2021 à 18:24, Javier Jimenez Shaw a écrit :
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.
You can call GetDataset() on the RasterBand returned by GetOverview().
Note that this will not necessarily return a non-NULL dataset for all
drivers, but it will for GeoTIFF.
Internally though this will go through the GDAL block cache (per band),
so there will be internal deinterlace & reinterlace, at least for
internal overviews, that by default use pixel-interleaving (for external
overviews, band interleaving is used)
Thanks
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Entre dos pensamientos racionales
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On Tue, 13 Jul 2021 at 14:04, Even Rouault <[email protected]
<mailto:[email protected]>> 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.
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hay infinitos pensamientos irracionales.
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