/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2004-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.geometry.jts;
import java.awt.Rectangle;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.opengis.referencing.operation.MathTransform;
import org.opengis.referencing.operation.TransformException;
import com.vividsolutions.jts.geom.Envelope;
import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryCollection;
import com.vividsolutions.jts.geom.LineString;
import com.vividsolutions.jts.geom.LinearRing;
import com.vividsolutions.jts.geom.MultiPoint;
import com.vividsolutions.jts.geom.Point;
import com.vividsolutions.jts.geom.Polygon;
/**
* Accepts geometries and collapses all the vertices that will be rendered to
* the same pixel. This class works only if the Geometries are based on
* {@link LiteCoordinateSequence} instances.
*
* @author jeichar
* @since 2.1.x
*
* @source $URL$
*/
public final class Decimator {
private static final Logger LOGGER = org.geotools.util.logging.Logging.getLogger(Decimator.class);
static final double DP_THRESHOLD;
static {
int threshold = -1;
String sthreshold = System.getProperty("org.geotools.decimate.dpThreshold");
if(sthreshold != null) {
try {
threshold = Integer.parseInt(sthreshold);
} catch(Throwable t) {
LOGGER.log(Level.WARNING, "Invalid value for org.geotools.decimate.dpThreshold, " +
"should be a positive integer but is: " + sthreshold);
}
}
DP_THRESHOLD = threshold;
}
private static final double EPS = 1e-9;
private double spanx = -1;
private double spany = -1;
/**
* Builds a decimator that will generalize geometries so that two subsequent points
* will be at least pixelDistance away from each other when painted on the screen.
* Set pixelDistance to 0 if you don't want any generalization (but just a transformation)
*
* @param screenToWorld
* @param paintArea
* @param pixelDistance
*/
public Decimator(MathTransform screenToWorld, Rectangle paintArea, double pixelDistance) {
if (screenToWorld != null && pixelDistance > 0) {
try {
double[] spans = computeGeneralizationDistances(screenToWorld, paintArea, pixelDistance);
this.spanx = spans[0];
this.spany = spans[1];
} catch(TransformException e) {
throw new RuntimeException("Could not perform the generalization spans computation", e);
}
} else {
this.spanx = 1;
this.spany = 1;
}
}
/**
* djb - noticed that the old way of finding out the decimation is based on
* the (0,0) location of the image. This is often wildly unrepresentitive of
* the scale of the entire map.
*
* A better thing to do is to decimate this on a per-shape basis (and use
* the shape's center). Another option would be to sample the image at
* different locations (say 9) and choose the smallest spanx/spany you find.
*
* Also, if the xform is an affine Xform, you can be a bit more aggressive
* in the decimation. If its not an affine xform (ie. its actually doing a
* CRS xform), you may find this is a bit too aggressive due to any number
* of mathematical issues.
*
* This is just a simple method that uses the centre of the given rectangle
* instead of (0,0).
*
* NOTE: this could need more work based on CRS, but the rectangle is in
* pixels so it should be fairly immune to all but crazy projections.
*
*
* @param screenToWorld
* @param paintArea
*/
public Decimator(MathTransform screenToWorld, Rectangle paintArea) {
// 0.8 is just so you don't decimate "too much". magic number.
this(screenToWorld, paintArea, 0.8);
}
/**
* Given a full transformation from screen to world and the paint area computes a best
* guess of the maxium generalization distance that won't make the transformations induced
* by the generalization visible on screen. <p>In other words, it computes how long a pixel
* is in the native spatial reference system of the data</p>
* @param screenToWorld
* @param paintArea
* @return
* @throws TransformException
*/
public static double[] computeGeneralizationDistances(MathTransform screenToWorld, Rectangle paintArea, double pixelDistance)
throws TransformException {
try {
// init the spans with the upper left corner
double[] spans = getGeneralizationSpans(paintArea.x, paintArea.y, screenToWorld);
// search over a simple 3x3 grid for higher spans so that we perform a basic sampling of the whole area
// and we pick the shortest generalization distances
for(int i = 0; i < 2; i++) {
for(int j = 0; j < 2; j++) {
double[] ns = getGeneralizationSpans(paintArea.x + paintArea.width * i / 2.0,
paintArea.y + paintArea.height / 2.0, screenToWorld);
if(ns[0] < spans[0])
spans[0] = ns[0];
if(ns[1] < spans[1])
spans[1] = ns[1];
}
}
spans[0] *= pixelDistance;
spans[1] *= pixelDistance ;
return spans;
} catch(TransformException e) {
// if we can't transform we went way out of the area of definition for the transform -> don't generalize
return new double[] {0, 0};
}
}
/**
* Computes the real world distance of a one pixel segment centered in the specified point
* @param x
* @param y
* @param transform
* @return
* @throws TransformException
*/
static double[] getGeneralizationSpans(double x, double y, MathTransform transform) throws TransformException {
double[] original = new double[] {
x - 0.5, y - 0.5,
x + 0.5, y + 0.5};
double[] transformed = new double[4];
transform.transform(original, 0, transformed, 0, 2);
double[] spans = new double[2];
spans[0] = Math.abs(transformed[0] - transformed[2]);
spans[1] = Math.abs(transformed[1] - transformed[3]);
return spans;
}
/**
* @throws TransformException
* @deprecated use the other constructor (with rectange) see javadox. This
* works fine, but it the results are often poor if you're also
* doing CRS xforms.
*/
public Decimator(MathTransform screenToWorld) {
this(screenToWorld, new Rectangle()); // do at (0,0)
}
public Decimator(double spanx, double spany) {
this.spanx = spanx;
this.spany = spany;
}
public final void decimateTransformGeneralize(Geometry geometry,
MathTransform transform) throws TransformException {
if (geometry instanceof GeometryCollection) {
GeometryCollection collection = (GeometryCollection) geometry;
final int length = collection.getNumGeometries();
for (int i = 0; i < length; i++) {
decimateTransformGeneralize(collection.getGeometryN(i),
transform);
}
} else if (geometry instanceof Point) {
LiteCoordinateSequence seq = (LiteCoordinateSequence) ((Point) geometry)
.getCoordinateSequence();
decimateTransformGeneralize(seq, transform, false);
} else if (geometry instanceof Polygon) {
Polygon polygon = (Polygon) geometry;
decimateTransformGeneralize(polygon.getExteriorRing(), transform);
final int length = polygon.getNumInteriorRing();
for (int i = 0; i < length; i++) {
decimateTransformGeneralize(polygon.getInteriorRingN(i),
transform);
}
} else if (geometry instanceof LineString) {
LineString ls = (LineString) geometry;
LiteCoordinateSequence seq = (LiteCoordinateSequence) ls.getCoordinateSequence();
boolean loop = ls instanceof LinearRing;
if(!loop && seq.size() > 1) {
double x0 = seq.getOrdinate(0, 0);
double y0 = seq.getOrdinate(0, 1);
double x1 = seq.getOrdinate(seq.size() - 1, 0);
double y1 = seq.getOrdinate(seq.size() - 1, 1);
loop = Math.abs(x0 - x1) < EPS &&
Math.abs(y0 - y1) < EPS;
}
decimateTransformGeneralize(seq, transform, loop);
}
}
/**
* decimates JTS geometries.
*/
public final void decimate(Geometry geom) {
if (spanx == -1)
return;
if (geom instanceof MultiPoint) {
// TODO check geometry and if its bbox is too small turn it into a 1
// point geom
return;
}
if (geom instanceof GeometryCollection) {
// TODO check geometry and if its bbox is too small turn it into a
// 1-2 point geom
// takes a bit of work because the geometry will need to be
// recreated.
GeometryCollection collection = (GeometryCollection) geom;
final int numGeometries = collection.getNumGeometries();
for (int i = 0; i < numGeometries; i++) {
decimate(collection.getGeometryN(i));
}
} else if (geom instanceof LineString) {
LineString line = (LineString) geom;
LiteCoordinateSequence seq = (LiteCoordinateSequence) line
.getCoordinateSequence();
if (decimateOnEnvelope(line, seq)) {
return;
}
decimate(line, seq);
} else if (geom instanceof Polygon) {
Polygon line = (Polygon) geom;
decimate(line.getExteriorRing());
final int numRings = line.getNumInteriorRing();
for (int i = 0; i < numRings; i++) {
decimate(line.getInteriorRingN(i));
}
}
}
/**
* @param geom
* @param seq
*/
private boolean decimateOnEnvelope(Geometry geom, LiteCoordinateSequence seq) {
Envelope env = geom.getEnvelopeInternal();
if (env.getWidth() <= spanx && env.getHeight() <= spany) {
if(geom instanceof LinearRing) {
decimateRingFully(seq);
return true;
} else {
double[] coords = seq.getArray();
int dim = seq.getDimension();
double[] newcoords = new double[dim * 2];
for (int i = 0; i < dim; i++) {
newcoords[i] = coords[i];
newcoords[dim + i] = coords[coords.length - dim + i];
}
seq.setArray(newcoords);
return true;
}
}
return false;
}
/**
* Makes sure the ring is turned into a minimal 3 non equal points one
* @param ring
*/
private void decimateRingFully(LiteCoordinateSequence seq) {
double[] coords = seq.getArray();
int dim = seq.getDimension();
// degenerate one, it's not even a triangle, or just a triangle
if(seq.size() <= 4)
return;
double[] newcoords = new double[dim * 4];
// assuming the ring makes sense in the first place (i.e., it's at least a triangle),
// we copy the first two and the last two points
for (int i = 0; i < dim; i++) {
newcoords[i] = coords[i];
newcoords[dim + i] = coords[dim + i];
newcoords[dim * 2 + i] = coords[coords.length - dim * 2 + i];
newcoords[dim * 3 + i] = coords[coords.length - dim + i];
}
seq.setArray(newcoords);
}
/**
* 1. remove any points that are within the spanx,spany. We ALWAYS keep 1st
* and last point 2. transform to screen coordinates 3. remove any points
* that are close (span <1)
*
* @param seq
* @param tranform
*/
private final void decimateTransformGeneralize(LiteCoordinateSequence seq,
MathTransform transform, boolean ring) throws TransformException {
// decimates before XFORM
int ncoords = seq.size();
double coords[] = seq.getXYArray(); // 2*#of points
if (ncoords < 2) {
if (ncoords == 1) // 1 coordinate -- just xform it
{
// double[] newCoordsXformed2 = new double[2];
if(transform != null) {
transform.transform(coords, 0, coords, 0, 1);
seq.setArray(coords, 2);
}
return;
} else
return; // ncoords =0
}
// if spanx/spany is -1, then no generalization should be done and all
// coordinates can just be transformed directly
if (spanx == -1 && spany == -1) {
// do the xform if needed
if ((transform != null) && (!transform.isIdentity())) {
transform.transform(coords, 0, coords, 0, ncoords);
seq.setArray(coords, 2);
}
return;
}
// generalize, use the heavier algorithm for longer lines
int actualCoords = spanBasedGeneralize(ncoords, coords);
if(DP_THRESHOLD > 0 && actualCoords > DP_THRESHOLD) {
actualCoords = dpBasedGeneralize(actualCoords, coords, Math.min(spanx, spany) * Math.min(spanx, spany));
}
// handle rings
if(ring && actualCoords <= 3) {
if(coords.length > 6) {
// normal rings
coords[2] = coords[2];
coords[3] = coords[3];
coords[4] = coords[4];
coords[5] = coords[5];
actualCoords = 3;
} else if(coords.length > 4){
// invalid rings, they do A-B-A, that is, two overlapping lines
coords[2] = coords[2];
coords[3] = coords[3];
actualCoords = 2;
}
}
// always have last one
coords[actualCoords * 2] = coords[(ncoords - 1) * 2];
coords[actualCoords * 2 + 1] = coords[(ncoords - 1) * 2 + 1];
actualCoords++;
// DO THE XFORM
if ((transform == null) || (transform.isIdentity())) {
// no actual xform
} else {
transform.transform(coords, 0, coords, 0, actualCoords);
}
// stick back into the coordinate sequence
if(actualCoords * 2 < coords.length) {
double[] seqDouble = new double[2 * actualCoords];
System.arraycopy(coords, 0, seqDouble, 0, actualCoords * 2);
seq.setArray(seqDouble, 2);
} else {
seq.setArray(coords, 2);
}
}
private int spanBasedGeneralize(int ncoords, double[] coords) {
int actualCoords = 1;
double lastX = coords[0];
double lastY = coords[1];
for (int t = 1; t < (ncoords - 1); t++) {
// see if this one should be added
double x = coords[t * 2];
double y = coords[t * 2 + 1];
if ((Math.abs(x - lastX) > spanx) || (Math.abs(y - lastY)) > spany) {
coords[actualCoords * 2] = x;
coords[actualCoords * 2 + 1] = y;
lastX = x;
lastY = y;
actualCoords++;
}
}
return actualCoords;
}
private int dpBasedGeneralize(int ncoords, double[] coords, double maxDistance) {
while(coords[0] == coords[(ncoords - 1) * 2] && coords[1] == coords[2 * ncoords - 1] && ncoords > 0) {
ncoords--;
}
if(ncoords == 0) {
return 0;
}
dpSimplifySection(0, ncoords - 1, coords, maxDistance);
int actualCoords = 1;
for(int i = 1; i < ncoords - 1; i++) {
final double x = coords[i * 2];
final double y = coords[i * 2 + 1];
if(!Double.isNaN(x)) {
coords[actualCoords * 2] = x;
coords[actualCoords * 2 + 1] = y;
actualCoords++;
}
}
return actualCoords;
}
private void dpSimplifySection(int first, int last, double[] coords, double maxDistanceSquared) {
if(last - 1 <= first) {
return;
}
double x0 = coords[first * 2];
double y0 = coords[first * 2 + 1];
double x1 = coords[last * 2];
double y1 = coords[last * 2 + 1];
double dx = x1 - x0;
double dy = y1 - y0;
double ls = dx * dx + dy * dy;
int idx = -1;
double dsmax = -1;
for (int i = first + 1; i < last; i++) {
double x = coords[i * 2];
double y = coords[i * 2 + 1];
double ds;
double r = ((x - x0) * dx + (y - y0) * dy) / ls;
if (r <= 0.0) {
ds = (x - x0) * (x - x0) + (y - y0) * (y - y0);
} else if (r >= 1.0) {
ds = (x - x1) * (x - x1) + (y - y1) * (y - y1);
} else {
double s = ((y0 - y) * dx - (x0 - x) *dy) / ls;
ds = s * s * ls;
}
if(idx == -1 || ds > dsmax) {
idx = i;
dsmax = ds;
}
}
if(dsmax <= maxDistanceSquared) {
for (int i = first + 1; i < last; i++) {
coords[i * 2] = Double.NaN;
coords[i * 2 + 1] = Double.NaN;
}
} else {
dpSimplifySection(first, idx, coords, maxDistanceSquared);
dpSimplifySection(idx, last, coords, maxDistanceSquared);
}
}
private void decimate(Geometry g, LiteCoordinateSequence seq) {
double[] coords = seq.getXYArray();
int dim = seq.getDimension();
int numDoubles = coords.length;
int readDoubles = 0;
double prevx, currx, prevy, curry, diffx, diffy;
for (int currentDoubles = 0; currentDoubles < numDoubles; currentDoubles += dim) {
if (currentDoubles >= dim && currentDoubles < numDoubles - dim) {
prevx = coords[readDoubles - dim];
currx = coords[currentDoubles];
diffx = Math.abs(prevx - currx);
prevy = coords[readDoubles - dim + 1];
curry = coords[currentDoubles + 1];
diffy = Math.abs(prevy - curry);
if (diffx > spanx || diffy > spany) {
readDoubles = copyCoordinate(coords, dim, readDoubles,
currentDoubles);
}
} else {
readDoubles = copyCoordinate(coords, dim, readDoubles,
currentDoubles);
}
}
if(g instanceof LinearRing && readDoubles < dim * 4) {
decimateRingFully(seq);
} else {
if(readDoubles < numDoubles) {
double[] newCoords = new double[readDoubles];
System.arraycopy(coords, 0, newCoords, 0, readDoubles);
seq.setArray(newCoords);
}
}
}
/**
* @param coords
* @param dimension
* @param readDoubles
* @param currentDoubles
*/
private int copyCoordinate(double[] coords, int dimension, int readDoubles,
int currentDoubles) {
for (int i = 0; i < dimension; i++) {
coords[readDoubles + i] = coords[currentDoubles + i];
}
readDoubles += dimension;
return readDoubles;
}
}