[Gvsig_english] thinking about raster reprojection...

[G. Allegri]

I've seen that on-the-fly raster reprojection isn't available yet. The only
solution, meanwhile, is doing a reprojection (wether during file loading or
as a distinct process) which is performed with a call to gdal warp (though
JNI calls from WarpFunction, right?).
This process can be ok for "offline" transformations, but become unfeasable
for on the fly uses, unless a very small grid is beaing loaded.
This is not Gvsig fault, it's the gdal reprojection code that has to do a
lot of work, even if an approximate reprojection is requested (error
threshold being > 0.0, the default in Gvsig).

A better solution could be to implement something like the Qgis
RasterReprojector [1], which is created and used during the read od the grid
datas, without affecting the providers code.
The raster projector implements a fast, approximated reprojections, which
can be ok for viewing the raster. An option coul be given to do a precise
reprojection in case raster processing need the original precision.

A hint for the gdalwarp reprojection: why don't let the user enter custom
projections in the Reproject dialog? We could make a check to validate its
syntax against the one accepted by gdal, or simply manage the exception in
case the projection is not valid...

Giovanni


[1]
http://trac.osgeo.org/qgis/browser/trunk/qgis/src/core/qgsrasterprojector.cpp
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