Selecting GeoRaster portions using SQL

Question

Hi,
I am interested in selecting a portion of an image stored in the GeoRaster format inside Oracle. After looking at the documentation, I can see there is something useful in the oracle.spatial.georaster.image.GeoRasterImage - in particular the method:
public RenderedImage getRasterImage(int pyramidLevel,JGeometry window)
However looking at the supplied code sample in the API:
//reading a GeoRaster object from database based on a query
ResultSet rs = statement.executeQuery("SELECT a.georaster FROM georaster_table a where a.georaster.rasterdatatable='RDT' and a.georaster.rasterid=1");
STRUCT geor = (oracle.sql.STRUCT) rs.getObject(1);
//construct a JGeoRaster object
JGeoRaster geoRaster = new JGeoRaster(geor);
//get GeoRasterImage instance
GeoRasterImage geoRasterImage=geoRaster.getGeoRasterImageObject();
//fetch a subset of GeoRaster object as a Java image
RenderedImage image=geoRasterImage.getRasterImage(0,0,0,100,100);
it can be seen that the code to get the resultset uses the unique raster ID to get the initial object, then later in the code the sub-image is retrieved using the pyramid level and coordinates desired.
But my question is this: getting the ResultSet in this manner requires the rasterid to be known ahead of time, which negates the whole reason/ability to select a sub-image based on coordinates/bounding box.
How do I do a SELECT statement using a bounding box and pyramid level?
Hopefully that makes sense
Thanks
MH

Answer 1

Thanks, that advice has gone a long way. This worked well, and I managed to retrieve a blob for the bounding box I provided, and know that there is data there (I wrote the binary directly to disk and it had an appropriate file size).
Now I'm trying to write the blob to a proper image file using this code:
ImageInputStream blobStream = ImageIO.createImageInputStream(img_blob.getBinaryStream());
BufferedImage img = ImageIO.read(blobStream);
String fileName = "image_chip_00.tif";
FileOutputStream out = new FileOutputStream(fileName);
TIFFEncodeParam encodeParam = new TIFFEncodeParam();
encodeParam.setCompression(TIFFEncodeParam.COMPRESSION_NONE);
ImageEncoder encoder = ImageCodec.createImageEncoder("TIFF", out, encodeParam);
encoder.encode(img);
Unfortunately it comes back with a NullPointerException for the last line of code, i.e. the "img" object is null. For some reason it has not been filled with the blob data (Note that I know the blob is being retrieved and contains data). This blob originates from a stored procedure I wrote using the getRasterSubset mentioned earlier.
Any ideas why the code may not be working?
On a similar but different approach, does the SDO_GEOR.subset function have a Java API equivalent? For this function, is the "inGeoraster IN SDO_GEORASTER" listed in the spec simply a georaster column name? It sounds like SDO_GEOR.subset is very similar to SDO_GEOR.getRasterSubset except that it returns a georaster object instead of a blob (with no metadata), respectively.
Thanks,
MH