[gdal-dev] Extracting (arbitrary?) overviews from ECW file

[Markus Schneider]

Dear list,

I am new to programming with GDAL (and to the ECW format). Let me say
thank you first, because my first experiences have been rather pleasant,
even if my setup is relatively involved (thanks everybody for providing
good documentation):

- Ubuntu 12.04 (AMD64)
- GDAL 1.10.1 (build from source)
- ECW SDK 5.0
- GDAL Java bindings

I successfully created a toy Java class for extracting regions from an
ECW file. Speed is impressive.

My observations/questions:

- If I understand correctly, ECW files internally do not have such a
thing as fixed overviews. However, ECW supports extraction of regions
with specified resolution on-the-fly. Is this correct?
- GDAL API reports overviews for ECW datasets. Having a first look at
the code, it seems to generate overview dimensions by subsequently
dividing height and width by two (until a minium side length of 128 has
been reached).

Final question: Is it possible to efficiently retrieve (regions of)
overviews at self-defined scales using the GDAL API? Or do I have to use
the ECW SDK for that?

Keep up the good work. Thanks for any pointers.

Best regards,
Markus

-- 
Markus Schneider
CEO

Occam Labs UG (haftungsbeschränkt)
Godesberger Allee 139
53175 Bonn, Germany

+49 228 93798874

http://www.occamlabs.de

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