Frank, thanks for your reply. Could you (or somebody else) give me a few more details how to get hold of a raster region with a resolution that is not defined by an overview?
Currently, I am able to extract regions from an overview using the following steps (in Java): ... Dataset dataset = gdal.Open( "dataset.ecw", GA_ReadOnly ); Band band = dataset.GetRasterBand( ... ); band = band.GetOverview(...); band.ReadRaster(x,y, ...) ... Afterwards, I have the raw data values in my array. It works fine for any overview. My problem is that I cannot figure out how to get hold of a Band for a non-predefined overview. How would I do this? Best regards, Markus Am 04.09.2013 18:15, schrieb Frank Warmerdam: > Markus, > > I believe the GDAL ECW driver will pass RasterIO() requests through to > the ECW SDK to evaluate meaning that there is no constraint based on the > advertized power-of-two overviews exposed from GDAL and no loss of quality. > > Best regards, > Frank > > > On Wed, Sep 4, 2013 at 6:52 AM, Markus Schneider <schnei...@occamlabs.de > <mailto:schnei...@occamlabs.de>> wrote: > > 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 <tel:%2B49%20228%2093798874> > > http://www.occamlabs.de > > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org <mailto:gdal-dev@lists.osgeo.org> > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > -- > ---------------------------------------+-------------------------------------- > I set the clouds in motion - turn up | Frank Warmerdam, > warmer...@pobox.com <mailto:warmer...@pobox.com> > light and sound - activate the windows | http://pobox.com/~warmerdam > and watch the world go round - Rush | Geospatial Software Developer -- Markus Schneider CEO Occam Labs UG (haftungsbeschränkt) Godesberger Allee 139 53175 Bonn, Germany +49 228 93798874 http://www.occamlabs.de
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