[Geotools-devel] Re: [Geoserver-devel] Raster Reprojection

[Martin D. <mar...@no...>]

Alession is right; LiteRenderer do not yet reproject rasters as far as I=20
know. J2D implements that, but the real work is actually done by the=20
GridCoverage "Resample" operation. J2D renderer doesn't do much more=20
than just invoking this "Resample" operation and cache the result.

The "Resample" operation is documented here:

http://modules.geotools.org/main/apidocs/org/geotools/coverage/processing=
/package-summary.html#Resample


There is an example about how to reproject a raster to targetCRS:

GridCoverage2D raster =3D ...
CoordinateReferenceSystem targetCRS =3D ...
GridCoverageProcessor2D processor =3D GridCoverageProcessor2D.getDefault(=
);
GridCoverage2D projected =3D processor.doOperation("Resample", raster,=20
"CoordinateReferenceSystem", targetCRS);

You can have more control if you also provide the "GridGeometry"=20
argument. If you don't, a default GridGeometry will be infered from the=20
source raster.

You may also try to play with the "InterpolationType" argument and see=20
if it improves the projection quality.



Jody Garnett a =E9crit :
>> Another problem is : is it correct to reproject raster on the fly?
>=20
> I am fairly sure it is - after all the alternative would be to load the=
=20
> whole image into memory - and we have the occasional 60 meg image file=20
> to play with.

JAI (which is used for most GridCoverage2D operations) splits images in=20
tiles. Only the required tiles will be loaded and computed. However, it=20
will work only if GridCoverageExchange (or Format, or whatever code is=20
used for loading images) take tiles in account. I have not yet looked at=20
the GridCoverageExchange code to see if it is the case, but we should be=20
able to improve the code in that direction.

	Martin.