[gdal-dev] Efficient raster bounding box transformation?

[Simon Eves]

So we are trying to optimize our raster import process, and particularly
the steps to derive the final WGS84/4326 bounding box for a raster file or
tile thereof.

Obviously in the general case, the transform is from integer pixel
coordinate through the Affine Transformation matrix and then whatever
OGRCoordinateTransformation is required to get to WGS84/4326, and perhaps a
GCP-based mesh transformation too.

Currently we are deriving the bounding box by passing all pixels of the
four edges of the file/tile through the full transform, except in the
simple Affine-only case where we just transform the four corners.

Is there any shortcut API provided by GDAL or PROJ to allow the bounding
box to be computed (or at least safely over-estimated) in the general case?
I'm assuming that even a non-GCP  OGRCT could still be non-linear such that
just transforming the corners is insufficient.

Thanks in advance,

Simon

-- 
Simon Eves
Senior Rendering Engineer
+1 (415) 902-1996
simon.eves at heavy.ai

<http://www.heavy.ai>
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