Le mercredi 21 décembre 2011 21:51:57, Yves Jacolin (free) a écrit : > Le mercredi 21 décembre 2011 21:44:14, Even Rouault a écrit : > > Le mercredi 21 décembre 2011 20:41:04, Yves Jacolin (free) a écrit : > > > Hello, > > > > > > I have some question about writing pixel functions with vrt files. I > > > have a netcdf file with two subset named U and V. > > > > > > How can I process sqrt(U^2 + V^2) using this feature with vrt file? > > > > > > * do I need to create a C file and build GADL with it? > > > * do I need to create a C file and locate it close to vrt file? > > > > It depends on how you want to use those pixel functions. If it is in an > > application in C/C++ that you develop and that uses GDAL, then it is > > sufficient to place the pixel function in your code and register it. > > > > If you want the pixel functions to be usable by existing GDAL utilities > > or third-party programs using GDAL (QGIS...), then a solution is to > > create a small shared library that will be loaded as a GDAL plugin. See > > http://trac.osgeo.org/gdal/ticket/3367 that has already a few functions. > > > > You just need to make sure that the plugin is accessible through > > GDAL_DRIVER_PATH environmenet variable. No need for it to be close to the > > VRT file. > > > > Or you can indeed hack GDAL itself and add it and register it. > > > > > Thanks, > > > > > > Y. > > interesting it seems we can use Python pixel functions.
I didn't dare to mention it because it is a bit geekie. You must use ctypes to load libgdal and then define manually each C function used. A bit more involved than the use of the typical GDAL Python bindings. > > Y. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
