[gdal-dev] Filesize too large when writing compressed float's to a Geotiff from Python

[Rutger]

Dear list,

When i try to write a floating point Geotiff from Python (both 32 or 64
bit), the resulting file size is significantly larger compared to the output
of gdal_translate. I wrote a small test script which tests this it for
various creation options like compression and block-sizes. It seems to be
the case for any compression method (packbits, lzw, deflate), and other
creation options don't seem to matter. Uncompressed data, or compressed
integers work fine, the file size matches gdal_translate very well.

Here is the notebook i used:
http://nbviewer.ipython.org/gist/RutgerK/27c4af235035621fb609

I would first all be interested to know if anyone can replicate this
behavior? And if there is something i can do to prevent this? I would rather
avoid having to run gdal_translate after each file written from Python. 

I'm running it on Windows 7 64bit. My GDAL version comes from the default
Conda repository which contains both bindings and utilities (at least for
version 1.11.1).

All i could find was this thread from 2010, it seems somewhat similar except
that there its about Uint16, for which it works for me:
http://osgeo-org.1560.x6.nabble.com/gdal-dev-RE-Compression-using-the-create-method-in-python-and-aggregation-methods-td3747703.html


Regards,
Rutger



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