Hello,
One approach that I use is to access the backing image of the grid
coverage, wrap it in a JAI (Java Advanced Imaging) TileImage object
and then use a JAI iterator to set values. So far this has worked
well for me, and takes advantage of JAI's ability to handle with
images that are too big to fit into available memory.
A simple example...
import javax.media.jai.TiledImage;
import javax.media.jai.iterator.RandomIterFactory;
import javax.media.jai.iterator.WritableRandomIter;
...
// create a TiledImage object that shares the coverage's image data
TiledImage tImg = new TiledImage(myCoverage.getRenderedImage(), true);
// create a writable iterator
WritableRandomIter iter = RandomIterFactory(timg, null);
// set a pixel value
float newValue = ...
int pixelX = ...
int pixelY = ...
int band = ...
iter.setSample(pixelX, pixelY, band, newValue);
If you need to work in the geo coordinate space rather than the
coverages image coordinate space...
MathTransform2D worldToGrid = null;
try {
worldToGrid = grid.getGridGeometry().getGridToCRS2D().inverse();
} catch (NoninvertibleTransformException ex) {
throw new RuntimeException("Could not create geographic to grid
coords transform");
}
Point2D geoCoords = ...
Point2D pixelCoords = new Point2D.Double();
try {
worldToGrid.transform(geoCoords, pixelCoords);
} catch (TransformException ex) {
throw new RuntimeException("Could not transform location");
}
I recall someone on the list saying that this TiledImage approach can
sometimes fail but so far it has worked well for me in this context
(if that someone - sorry memory fails me - has more details on this
please chime in).
For one of my own projects where I needed to regularly update coverage
values, I wrote a class that wraps GridCoverage2D and provides setter
methods that cache the new values. When the coverage is queried or
rendered the cache is flushed and the values written to the coverages
backing image using the method described above. Happy to share that
code if it sounds applicable to your case.
Michael
2009/5/11 zeng <[email protected]>:
> Hi, all
> I want to write a function has a gridcoverage2d parameter and return a
> gridcoverage2d, what need I do is to change the samples value of the raster.
> I don't want to create a new gridcoverage2d and return it, is there any way?
>
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