[gdal-dev] COG and VRT behaviour

[thomas bonfort]

There are only very specific cases where it would be valid to directly copy
overview tiles, namely if both image sizes are an exact power of 2. I'll
let Even contradict me if I'm wrong, but I highly doubt that what you are
trying to do is possible.
regards,
Thomas

Le jeu. 6 oct. 2022, 05:58, Ian Reese <xycarto at gmail.com> a écrit :

> Hi GDAL,
>
> Let's say I have two GTiff files in COG format:
>
> f1.tif
> f2.tif
>
> f1.tif and f2.tif are created like so:
>
> gdal_translate input.tif f1.tif \
> -of COG \
> -co BLOCKSIZE=256 \
> -co COMPRESS=JPEG \
>
> I can easily create a vrt of these two COGs and get the expected behaviour
> where the VRT honours the overviews of the f1 and f2 COGs.
>
> gdalbuildvrt cog.vrt f1.tif f2.tif
>
> This is my question, is it possible to create a COG Tif from this VRT that
> copies over the overviews from each COG in the VRT?
>
> For example something like:
>
> gdal_translate cog.vrt cog.tif -of COG -co OVERVIEWS=FORCE_USE_EXISTING
>
> I suspect this may not be possible. My guess is that translate is confused
> by which overviews to use when creating the single cog.tif? Or that when I
> created f1.tif and f2.tif I missed a setting?
>
> I have tried many combinations to get this to work, but I think it might
> be time to ask the experts. Any insight to this would be greatly
> appreciated.
>
> Cheer,
>
> Ianto
>
> --
> Ian C Reese
> https://xycarto.com
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