Markus,<br><br>If I understand your problem correctly you should be able to use GDALDataset::BuildOverviews() and/or GDALRegenerateOverviews() for this task.<br>To avoid a temporary file, you can use a <a href="http://www.gdal.org/gdal_vrttut.html">GDAL virtual file</a>.<br>
There is an example python code using these functions at <span><a href="http://trac.osgeo.org/gdal/browser/trunk/autotest/gcore/tiff_ovr.py">http://trac.osgeo.org/gdal/browser/trunk/autotest/gcore/tiff_ovr.py</a> . You can find the documentation for the C++ version of these functions at <a href="http://www.gdal.org/classGDALDataset.html#2aa6f88b3bbc840a5696236af11dde15">http://www.gdal.org/classGDALDataset.html#2aa6f88b3bbc840a5696236af11dde15</a> and <a href="http://www.gdal.org/gdal_8h.html#f42fd5ddd2d160492b23d62e75e42c82">http://www.gdal.org/gdal_8h.html#f42fd5ddd2d160492b23d62e75e42c82</a> .<br>
</span>You may need to use the trunk version of GDAL (refer to <a href="http://trac.osgeo.org/gdal/wiki/DownloadSource#Subversion">http://trac.osgeo.org/gdal/wiki/DownloadSource#Subversion</a>) for these functions.<br>I hope this can solve your problem.<br>
<br>Best regards,<br>-- <br>Chaitanya kumar CH.<br><br><div class="gmail_quote">On Tue, Jun 23, 2009 at 4:29 PM, Markus Reinhold <span dir="ltr"><<a href="mailto:leaffan@gmx.net">leaffan@gmx.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Hej everyone,<br>
currently I was able to finish a small Python project utilizing GDAL for creating quicklooks of satellite imagery. What I am doing right now is<br>
retrieving the statistics of input bands, applying a standard deviation<br>
stretch and saving the result as PNG-dataset. This works quite well,<br>
however my problems start right here. To actually resize the created<br>
dataset and to merge three separate bands into a single PNG-file I'm<br>
using the Python Imaging Library, which needs single files to read from<br>
in order to do any processing. There is no problem with small to<br>
medium-sized images. But I'm running into trouble trying to create a<br>
quicklook for some standard panchromatic Quickbird imagery (ca. 30000 x<br>
30000 pixels, 0.6 m GSD at UInt16 -> about 1.9 GB file size) as the PNG<br>
file that is created temporarily gets very big. The neccessary I/O<br>
operations naturally take quite some time. So my question is the<br>
following: Is there any possibility to do resizing a dataset with GDAL<br>
means - to spare the creation of a temporary file?<br>
Thank you very much for any ideas.<br>
Regards,<br>
Markus Reinhold<br>
<br>
-- <br>
<br>
********************************************************<br>
Dipl.-Kartograph Markus Reinhold<br>
<br>
Chair of Geoinformatics, Geohydrology and Modeling<br>
Friedrich-Schiller-University Jena<br>
Löbdergraben 32<br>
D - 07743 Jena<br>
Germany<br>
<br>
Phone.: (+49)(0)3641 / 9 488 65<br>
E-Mail: <a href="mailto:markus.reinhold@uni-jena.de" target="_blank">markus.reinhold@uni-jena.de</a><br>
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