/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2005-2008, 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.
*
*
* This class is composed of code taken from JAI-tools version 1.1.0
* http://code.google.com/p/jai-tools/
*
* It combines the JAI-tools classes AbstractSmoother, LineSmoother,
* PolygonSmoother and SmootherControl. All are covered by the following
* copyright and license:
*
* Copyright 2010-2011 Michael Bedward
*
* This file is part of jai-tools.
*
* jai-tools 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, either version 3 of the
* License, or (at your option) any later version.
*
* jai-tools 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.
*
* You should have received a copy of the GNU Lesser General Public
* License along with jai-tools. If not, see <http://www.gnu.org/licenses/>.
*/
package org.geotools.geometry.jts;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.vividsolutions.jts.geom.Coordinate;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.geom.LineString;
import com.vividsolutions.jts.geom.LinearRing;
import com.vividsolutions.jts.geom.Polygon;
/**
* Provides package-private helper methods for the {@link JTS}
* utility class.
*
* @author Michael Bedward
*
* @source $URL$
* @version $Id$
* @since 2.8
*/
class GeometrySmoother {
/**
* Defines methods to control the smoothing process.
* {@code LineSmoother} has a default implementation
* that specifies a constant number of vertices in smoothed
* segments and no lower bound on the distance between
* input vertices for smoothing.
*/
private interface SmootherControl {
/**
* Gets the minimum distance between input vertices
* for the segment to be smoothed. Segments smaller
* than this will be copied to the output unchanged.
*
* @return minimum segment length for smoothing
*/
double getMinLength();
/**
* Given an input segment length, returns the number
* of vertices to use for the smoothed segment. This
* number includes the segment end-points.
*
* @param length input segment length
*
* @return number of vertices in the smoothed segment
* including the end-points
*/
int getNumVertices(double length);
}
/**
* Default smoothing control. Specifies no minimum
* vertex distance and a constant number of points
* per smoothed segment.
*/
private SmootherControl DEFAULT_CONTROL = new SmootherControl() {
public double getMinLength() {
return 0.0;
}
public int getNumVertices(double length) {
return 10;
}
};
/** The current SmootherControl instance. */
private SmootherControl control;;
/** The current {@code GeometryFactory} being used. */
private final GeometryFactory geomFactory;
/**
* Class to hold interpolation parameters for a given point.
*/
private static final class InterpPoint {
double[] t = new double[4];
double tsum;
}
/**
* Cache of previously calculated interpolation parameters
*/
private Map<Integer, WeakReference<InterpPoint[]>> lookup =
new HashMap<Integer, WeakReference<InterpPoint[]>>();
/**
* Creates a new smoother that will use the given {@code GeometryFactory}.
*
* @param geomFactory factory to use for creating smoothed objects
*
* @throws IllegalArgumentException if {@code geomFactory} is {@code null}
*/
GeometrySmoother(GeometryFactory geomFactory) {
if (geomFactory == null) {
throw new IllegalArgumentException("geomFactory must not be null");
}
this.geomFactory = geomFactory;
this.control = DEFAULT_CONTROL;
}
/**
* Creates a new {@code LineString} which is a smoothed version of
* the input {@code LineString}.
*
* @param ls the input {@code LineString}
*
* @param alpha a value between 0 and 1 (inclusive) specifying the tightness
* of fit of the smoothed boundary (0 is loose)
*
* @return the smoothed {@code LineString}
*/
LineString smooth(LineString ls, double alpha) {
Coordinate[] coords = ls.getCoordinates();
Coordinate[][] controlPoints = getLineControlPoints(coords, alpha);
final int N = coords.length;
List<Coordinate> smoothCoords = new ArrayList<Coordinate>();
double dist;
for (int i = 0; i < N - 1; i++) {
dist = coords[i].distance(coords[i+1]);
if (dist < control.getMinLength()) {
// segment too short - just copy input coordinate
smoothCoords.add(new Coordinate(coords[i]));
} else {
int smoothN = control.getNumVertices(dist);
Coordinate[] segment = cubicBezier(
coords[i], coords[i+1],
controlPoints[i][1], controlPoints[i+1][0],
smoothN);
int copyN = i < N - 1 ? segment.length - 1 : segment.length;
for (int k = 0; k < copyN; k++) {
smoothCoords.add(segment[k]);
}
}
}
smoothCoords.add(coords[N - 1]);
return geomFactory.createLineString(smoothCoords.toArray(new Coordinate[0]));
}
/**
* Creates a new {@code Polygon} whose exterior shell is a smoothed
* version of the input {@code Polygon}.
* <p>
* Note: this method presently ignores holes.
*
* @param p the input {@code Polygon}
*
* @param alpha a value between 0 and 1 (inclusive) specifying the tightness
* of fit of the smoothed boundary (0 is loose)
*
* @return the smoothed {@code Polygon}
*/
public Polygon smooth(Polygon p, double alpha) {
Coordinate[] coords = p.getExteriorRing().getCoordinates();
final int N = coords.length - 1; // first coord == last coord
Coordinate[][] controlPoints = getPolygonControlPoints(coords, N, alpha);
List<Coordinate> smoothCoords = new ArrayList<Coordinate>();
double dist;
for (int i = 0; i < N; i++) {
int next = (i + 1) % N;
dist = coords[i].distance(coords[next]);
if (dist < control.getMinLength()) {
// segment too short - just copy input coordinate
smoothCoords.add(new Coordinate(coords[i]));
} else {
int smoothN = control.getNumVertices(dist);
Coordinate[] segment = cubicBezier(
coords[i], coords[next],
controlPoints[i][1], controlPoints[next][0],
smoothN);
int copyN = i < N - 1 ? segment.length - 1 : segment.length;
for (int k = 0; k < copyN; k++) {
smoothCoords.add(segment[k]);
}
}
}
LinearRing shell = geomFactory.createLinearRing(smoothCoords.toArray(new Coordinate[0]));
return geomFactory.createPolygon(shell, null);
}
/**
* Sets a new {@code Control} object to for smoothing.
*
* @param control the control to use for smoothing; if {@code null} the
* default control will be set
*/
void setControl(SmootherControl control) {
this.control = control == null ? DEFAULT_CONTROL : control;
}
/**
* Calculates a pair of Bezier control points for each vertex in an
* array of {@code Coordinates}.
*
* @param coords input vertices
* @param N number of coordinates in {@coords} to use
* @param alpha tightness of fit
*
* @return 2D array of {@code Coordinates} for positions of each pair of
* control points per input vertex
*/
private Coordinate[][] getLineControlPoints(Coordinate[] coords, double alpha) {
if (alpha < 0.0 || alpha > 1.0) {
throw new IllegalArgumentException("alpha must be a value between 0 and 1 inclusive");
}
final int N = coords.length;
Coordinate[][] ctrl = new Coordinate[N][2];
Coordinate[] v = new Coordinate[3];
Coordinate[] mid = new Coordinate[2];
mid[0] = new Coordinate();
mid[1] = new Coordinate();
Coordinate anchor = new Coordinate();
double[] vdist = new double[2];
// double mdist;
// Start with dummy coordinate preceding first real coordinate
v[1] = new Coordinate(
2 * coords[0].x - coords[1].x, 2 * coords[0].y - coords[1].y);
v[2] = coords[0];
// Dummy coordinate for end of line
Coordinate vN = new Coordinate(
2 * coords[N-1].x - coords[N-2].x,
2 * coords[N-1].y - coords[N-2].y);
mid[1].x = (v[1].x + v[2].x) / 2.0;
mid[1].y = (v[1].y + v[2].y) / 2.0;
vdist[1] = v[1].distance(v[2]);
for (int i = 0; i < N; i++) {
v[0] = v[1];
v[1] = v[2];
v[2] = (i < N - 1 ? coords[i + 1] : vN);
mid[0].x = mid[1].x;
mid[0].y = mid[1].y;
mid[1].x = (v[1].x + v[2].x) / 2.0;
mid[1].y = (v[1].y + v[2].y) / 2.0;
vdist[0] = vdist[1];
vdist[1] = v[1].distance(v[2]);
double p = vdist[0] / (vdist[0] + vdist[1]);
anchor.x = mid[0].x + p * (mid[1].x - mid[0].x);
anchor.y = mid[0].y + p * (mid[1].y - mid[0].y);
double xdelta = anchor.x - v[1].x;
double ydelta = anchor.y - v[1].y;
ctrl[i][0] = new Coordinate(
alpha*(v[1].x - mid[0].x + xdelta) + mid[0].x - xdelta,
alpha*(v[1].y - mid[0].y + ydelta) + mid[0].y - ydelta);
ctrl[i][1] = new Coordinate(
alpha*(v[1].x - mid[1].x + xdelta) + mid[1].x - xdelta,
alpha*(v[1].y - mid[1].y + ydelta) + mid[1].y - ydelta);
}
return ctrl;
}
/**
* Calculates a pair of Bezier control points for each vertex in an
* array of {@code Coordinates}.
*
* @param coords input vertices
* @param N number of coordinates in {@coords} to use
* @param alpha tightness of fit
*
* @return 2D array of {@code Coordinates} for positions of each pair of
* control points per input vertex
*/
private Coordinate[][] getPolygonControlPoints(Coordinate[] coords, int N, double alpha) {
if (alpha < 0.0 || alpha > 1.0) {
throw new IllegalArgumentException("alpha must be a value between 0 and 1 inclusive");
}
Coordinate[][] ctrl = new Coordinate[N][2];
Coordinate[] v = new Coordinate[3];
Coordinate[] mid = new Coordinate[2];
mid[0] = new Coordinate();
mid[1] = new Coordinate();
Coordinate anchor = new Coordinate();
double[] vdist = new double[2];
//double mdist;
v[1] = coords[N - 1];
v[2] = coords[0];
mid[1].x = (v[1].x + v[2].x) / 2.0;
mid[1].y = (v[1].y + v[2].y) / 2.0;
vdist[1] = v[1].distance(v[2]);
for (int i = 0; i < N; i++) {
v[0] = v[1];
v[1] = v[2];
v[2] = coords[(i + 1) % N];
mid[0].x = mid[1].x;
mid[0].y = mid[1].y;
mid[1].x = (v[1].x + v[2].x) / 2.0;
mid[1].y = (v[1].y + v[2].y) / 2.0;
vdist[0] = vdist[1];
vdist[1] = v[1].distance(v[2]);
double p = vdist[0] / (vdist[0] + vdist[1]);
anchor.x = mid[0].x + p * (mid[1].x - mid[0].x);
anchor.y = mid[0].y + p * (mid[1].y - mid[0].y);
double xdelta = anchor.x - v[1].x;
double ydelta = anchor.y - v[1].y;
ctrl[i][0] = new Coordinate(
alpha*(v[1].x - mid[0].x + xdelta) + mid[0].x - xdelta,
alpha*(v[1].y - mid[0].y + ydelta) + mid[0].y - ydelta);
ctrl[i][1] = new Coordinate(
alpha*(v[1].x - mid[1].x + xdelta) + mid[1].x - xdelta,
alpha*(v[1].y - mid[1].y + ydelta) + mid[1].y - ydelta);
}
return ctrl;
}
/**
* Calculates vertices along a cubic Bazier curve given start point, end point
* and two control points.
*
* @param start start position
* @param end end position
* @param ctrl1 first control point
* @param ctrl2 second control point
* @param nv number of vertices including the start and end points
*
* @return vertices along the Bezier curve
*/
private Coordinate[] cubicBezier(final Coordinate start, final Coordinate end,
final Coordinate ctrl1, final Coordinate ctrl2, final int nv) {
final Coordinate[] curve = new Coordinate[nv];
final Coordinate[] buf = new Coordinate[3];
for (int i = 0; i < buf.length; i++) {
buf[i] = new Coordinate();
}
curve[0] = new Coordinate(start);
curve[nv - 1] = new Coordinate(end);
InterpPoint[] ip = getInterpPoints(nv);
for (int i = 1; i < nv-1; i++) {
Coordinate c = new Coordinate();
c.x = ip[i].t[0]*start.x + ip[i].t[1]*ctrl1.x + ip[i].t[2]*ctrl2.x + ip[i].t[3]*end.x;
c.x /= ip[i].tsum;
c.y = ip[i].t[0]*start.y + ip[i].t[1]*ctrl1.y + ip[i].t[2]*ctrl2.y + ip[i].t[3]*end.y;
c.y /= ip[i].tsum;
curve[i] = c;
}
return curve;
}
/**
* Gets the interpolation parameters for a Bezier curve approximated
* by the given number of vertices.
*
* @param npoints number of vertices
*
* @return array of {@code InterpPoint} objects holding the parameter values
*/
private InterpPoint[] getInterpPoints(int npoints) {
WeakReference<InterpPoint[]> ref = lookup.get(npoints);
InterpPoint[] ip = null;
if (ref != null) ip = ref.get();
if (ip == null) {
ip = new InterpPoint[npoints];
for (int i = 0; i < npoints; i++) {
double t = (double) i / (npoints - 1);
double tc = 1.0 - t;
ip[i] = new InterpPoint();
ip[i].t[0] = tc*tc*tc;
ip[i].t[1] = 3.0*tc*tc*t;
ip[i].t[2] = 3.0*tc*t*t;
ip[i].t[3] = t*t*t;
ip[i].tsum = ip[i].t[0] + ip[i].t[1] + ip[i].t[2] + ip[i].t[3];
}
lookup.put(npoints, new WeakReference<InterpPoint[]>(ip));
}
return ip;
}
}