Hi Zeng,
I'm posting the code here so that if anyone else spots glaring errors
in it they can warn you :-)
Note, in my app I was only working with double valued, single-band
coverages but it would be easy to extend this class to deal with more
types and multi-band data.
Let me know if you have any problems with it.
Michael
package org.cafeanimal.geo.gridlayer;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.image.DataBuffer;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import javax.media.jai.TiledImage;
import javax.media.jai.iterator.RandomIterFactory;
import javax.media.jai.iterator.WritableRandomIter;
import javax.media.jai.operator.FormatDescriptor;
import org.geotools.coverage.grid.GridCoverage2D;
import org.geotools.geometry.Envelope2D;
import org.geotools.image.ImageWorker;
import org.opengis.coverage.PointOutsideCoverageException;
import org.opengis.geometry.Envelope;
import org.opengis.referencing.operation.MathTransform2D;
import org.opengis.referencing.operation.NoninvertibleTransformException;
import org.opengis.referencing.operation.TransformException;
/**
*
* @author Michael Bedward and Murray Ellis
*/
public class WritableGridCoverage {
private GridCoverage2D gridCov;
private MathTransform2D worldToGrid = null;
private double[] dbuf = new double[1];
private static final int MAX_PENDING_VALUES = 10000;
private static class PendingValue {
Point2D.Double pos;
boolean isGeographic;
double value;
}
private List<PendingValue> pendingValues = new ArrayList<PendingValue>();
/**
* Constructor
* @param gridCov the GridCoverage2D object to be wrapped
*/
public WritableGridCoverage(GridCoverage2D gridCov) {
this.gridCov = gridCov;
}
public GridCoverage2D getGridCoverage() {
flushCache(true);
return gridCov;
}
public String getName() {
return gridCov.getName().toString();
}
public int getNumRows() {
return gridCov.getRenderedImage().getHeight();
}
public int getNumCols() {
return gridCov.getRenderedImage().getWidth();
}
public Rectangle2D.Double getBounds() {
Envelope2D env = gridCov.getEnvelope2D();
return new Rectangle2D.Double(env.x, env.y, env.width, env.height);
}
public double getPixelWidth() {
return gridCov.getEnvelope2D().getWidth() / getNumCols();
}
public double getValueAtPos(Point2D pos) {
flushCache(true);
try {
gridCov.evaluate(pos, dbuf);
} catch (PointOutsideCoverageException ex) {
return Double.NaN;
}
return dbuf[0];
}
public int getValueAtPosAsInt(Point2D pos, int defaultValue) {
double val = getValueAtPos(pos);
if (Double.isNaN(val)) {
return defaultValue;
} else {
return (int) Math.round(val);
}
}
public double[] getValuesAtPos(Point2D pos, double[] buf) {
flushCache(true);
if (buf == null) {
buf = new double[gridCov.getNumSampleDimensions()];
}
try {
buf = gridCov.evaluate(pos, buf);
} catch (PointOutsideCoverageException ex) {
Arrays.fill(buf, Double.NaN);
}
return buf;
}
public void saveAsJPEG(File path) {
try {
ImageWorker iw = new ImageWorker(gridCov.getRenderedImage());
if (!iw.isBytes()) {
iw.setImage(FormatDescriptor.create(gridCov.getRenderedImage(),
DataBuffer.TYPE_BYTE, null));
}
iw.write(path);
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
public void setValueAtPos(Point2D pos, int value) {
Number n = Integer.valueOf(value);
doSetValue(pos, n);
}
public void setValueAtPos(Point2D pos, float value) {
Number n = new Float(value);
doSetValue(pos, n);
}
public void setValueAtPos(Point2D pos, double value) {
Number n = new Double(value);
doSetValue(pos, n);
}
private void doSetValue(Point2D pos, Number value) {
PendingValue pv = new PendingValue();
pv.pos = new Point2D.Double(pos.getX(), pos.getY());
pv.isGeographic = true;
pv.value = value.doubleValue();
pendingValues.add(pv);
flushCache(false);
}
private void flushCache(boolean force) {
if (pendingValues.size() >= MAX_PENDING_VALUES || (force &&
pendingValues.size() > 0)) {
if (worldToGrid == null) {
try {
worldToGrid =
gridCov.getGridGeometry().getGridToCRS2D().inverse();
} catch (NoninvertibleTransformException ex) {
throw new RuntimeException("Could not create
geographic to grid coords transform");
}
}
TiledImage tImg = new TiledImage(gridCov.getRenderedImage(), true);
WritableRandomIter writeIter =
RandomIterFactory.createWritable(tImg, null);
Point2D.Double gridPos = new Point2D.Double();
for (PendingValue pv : pendingValues) {
if (pv.isGeographic) {
try {
worldToGrid.transform(pv.pos, gridPos);
} catch (TransformException ex) {
throw new RuntimeException("Could not
transform location [" +
pv.pos + "] to grid coords");
}
} else {
gridPos.setLocation(pv.pos);
}
writeIter.setSample((int) gridPos.x, (int) gridPos.y,
0, pv.value);
}
pendingValues.clear();
String name = getName();
Envelope env = gridCov.getEnvelope();
}
}
}
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