[gdal-dev] Downscaled geotiff with overviews

[Javier Jimenez Shaw]

Hi

I want to make a (power-of-two) downscaled version of a geotiff with
overviews efficiently with C++ (not from the console).

Let's say I have a geotiff with overviews (external or internal), and I
want a copy of it, but at 50% of the size. That is just removing the "base"
of the pyramid, but keeping all the other levels. Then voilà, there you
have the geotiff 50% smaller, with the overviews already there, almost
without any computation. The same for 25% (and any power of 2).

However I do not figure out how to do it efficiently in C++. If I
understand correctly, CreateCopy is producing an image with the same size.
So to downscale I have to create a new image, read downscaled (that will
use the overviews) and write. But later, I have to recreate the overviews
on the new image... that are already in the original image.

Is there any way to make it efficiently? (as we have the data there)

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