ingo@1115: /*
ingo@1115:  * Copyright (c) 2010 by Intevation GmbH
ingo@1115:  *
ingo@1115:  * This program is free software under the LGPL (>=v2.1)
ingo@1115:  * Read the file LGPL.txt coming with the software for details
ingo@1115:  * or visit http://www.gnu.org/licenses/ if it does not exist.
ingo@1115:  */
ingo@1115: 
sascha@361: package de.intevation.gnv.math;
sascha@361: 
sascha@593: import com.vividsolutions.jts.geom.Coordinate;
sascha@593: import com.vividsolutions.jts.geom.Envelope;
sascha@593: 
sascha@361: import java.util.Comparator;
sascha@361: 
sascha@593: import org.apache.log4j.Logger;
sascha@361: 
sascha@361: /**
sascha@798:  * Point which besides the x, y, z coodinates has an index i, j pair
sascha@798:  * to model neighborhood.
sascha@798:  * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a>
sascha@361:  */
sascha@361: public class Point2d
sascha@361: extends      Coordinate
sascha@361: {
sascha@593:     private static Logger log = Logger.getLogger(Point2d.class);
sascha@593: 
sascha@798:     /**
sascha@798:      * Numerical tolerance epsilon: {@value}
sascha@798:      */
ingo@365:     public static final double EPSILON = 1e-3d;
sascha@361: 
sascha@798:     /**
sascha@798:      * Compares two Point2ds by their x coordinates
sascha@798:      */
sascha@361:     public static final Comparator X_COMPARATOR = new Comparator() {
sascha@361:         public int compare(Object a, Object b) {
sascha@361:             double xa = ((Coordinate)a).x;
sascha@361:             double xb = ((Coordinate)b).x;
sascha@361:             if (xa < xb) return -1;
sascha@361:             if (xa > xb) return +1;
sascha@361:             return 0;
sascha@361:         }
sascha@361:     };
sascha@361: 
sascha@798:     /**
sascha@798:      * Compares two Point2ds by their y coordinates.
sascha@798:      */
sascha@361:     public static final Comparator Y_COMPARATOR = new Comparator() {
sascha@361:         public int compare(Object a, Object b) {
sascha@361:             double ya = ((Coordinate)a).y;
sascha@361:             double yb = ((Coordinate)b).y;
sascha@361:             if (ya < yb) return -1;
sascha@361:             if (ya > yb) return +1;
sascha@361:             return 0;
sascha@361:         }
sascha@361:     };
sascha@361: 
sascha@798:     /**
sascha@798:      * The i index of this Point2d.
sascha@798:      */
sascha@361:     public int i;
sascha@798:     /**
sascha@798:      * The j index of this Point2d.
sascha@798:      */
sascha@361:     public int j;
sascha@361: 
sascha@798:     /**
sascha@798:      * Default constructor.
sascha@798:      */
sascha@361:     public Point2d() {
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      * Constructor setting x and y coordinate.
sascha@798:      * @param x The x coordinate.
sascha@798:      * @param y The y coordinate.
sascha@798:      */
sascha@593:     public Point2d(double x, double y) {
sascha@593:         super(x, y);
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Constructor setting x, y and i, j.
sascha@798:      * @param x The x coordinate.
sascha@798:      * @param y The y coordinate.
sascha@798:      * @param i The i index.
sascha@798:      * @param j The j index.
sascha@798:      */
sascha@431:     public Point2d(double x, double y, int i, int j) {
sascha@431:         super(x, y);
sascha@431:         this.i = i;
sascha@431:         this.j = j;
sascha@431:     }
sascha@431: 
sascha@798:     /**
sascha@798:      * Constructor setting x, y, z and i, j.
sascha@798:      * @param x The x coordinate.
sascha@798:      * @param y The y coordinate.
sascha@798:      * @param z The z coordinate.
sascha@798:      * @param i The i index.
sascha@798:      * @param j The j index.
sascha@798:      */
sascha@361:     public Point2d(double x, double y, double z, int i, int j) {
sascha@361:         super(x, y, z);
sascha@361:         this.i = i;
sascha@361:         this.j = j;
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      * Calculates the L1 distance to another Point2d.
sascha@798:      * @param other The other Point2d.
sascha@798:      * @return The L1 distance.
sascha@798:      */
sascha@361:     public double L1(Point2d other) {
sascha@798:         return L1Comparator.L1(this, other);
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      * Creates an envelope around this Point2d with
sascha@798:      * the numerical tolerance of {@link #EPSILON}.
sascha@798:      * @return The envelope.
sascha@798:      */
sascha@361:     public Envelope envelope() {
sascha@361:         return envelope(EPSILON);
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      *Creates an envelope around this Point2d with
sascha@798:      * a given tolerance.
sascha@798:      * @param epsilon The tolerance in all directions.
sascha@798:      * @return The envelope.
sascha@798:      */
sascha@361:     public Envelope envelope(double epsilon) {
sascha@361:         return new Envelope(
sascha@361:             x-epsilon, x+epsilon,
sascha@361:             y-epsilon, y+epsilon);
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      * Given this and another Point2d it looks if there is
sascha@798:      * a gap between the in points in i index direction.
sascha@798:      * @param other The other Point2d.
sascha@798:      * @return true if there is is a gap, else false.
sascha@798:      */
sascha@361:     public boolean hasIGap(Point2d other) {
sascha@361:         return Math.abs(i - other.i) > 1;
sascha@361:     }
sascha@361: 
sascha@798:     /**
sascha@798:      * Given this and another Point2d it looks if there is
sascha@798:      * a gap between the in points in j index direction.
sascha@798:      * @param other The other Point2d.
sascha@798:      * @return true if there is is a gap, else false.
sascha@798:      */
sascha@361:     public boolean hasJGap(Point2d other) {
sascha@361:         return Math.abs(j - other.j) > 1;
sascha@361:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Given this and another Point2d a new Point2d is
sascha@798:      * created via {@link #newPoint() }. The x, y coordinate
sascha@798:      * of the new point is on the line of this and the other
sascha@798:      * given point at a given scaling point.
sascha@798:      * @param t The scaling factor.
sascha@798:      * @param other The other point.
sascha@798:      * @return The new Point2d.
sascha@798:      */
sascha@593:     public Point2d extrapolate(double t, Point2d other) {
sascha@593:         if (other == null) {
sascha@593:             return null;
sascha@593:         }
sascha@593:         Point2d p = newPoint();
sascha@593:         p.x = t*(other.x - x) + x;
sascha@593:         p.y = t*(other.y - y) + y;
sascha@593:         return p;
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Creates a new Point2d or an instance of a subclass.
sascha@798:      * Override this in subclasses.
sascha@798:      * @return The new Point2d.
sascha@798:      */
sascha@593:     public Point2d newPoint() {
sascha@593:         return new Point2d(0d, 0d);
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Creates a new Point2d or an instance of a subclass
sascha@798:      * at a given coordinate.
sascha@798:      * Override this in subclasses.
sascha@798:      * @param x The x coordinate.
sascha@798:      * @param y The y coordinate.
sascha@798:      * @return The new point.
sascha@798:      */
sascha@593:     public Point2d newPoint(double x, double y) {
sascha@593:         return new Point2d(x, y);
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Sets the z value to the inverse distance weighting (IDW) value
sascha@798:      * of the z values of a set of given points.
sascha@798:      * @param ps The points from wich the z values are taken
sascha@798:      * to calculate the IDW.
sascha@798:      */
sascha@593:     public void inverseDistanceWeighting(Point2d [] ps) {
sascha@593: 
sascha@593:         double sum = 0d;
sascha@593: 
sascha@593:         double [] d = new double[ps.length];
sascha@593: 
sascha@593:         for (int i = 0; i < ps.length; ++i) {
sascha@593:             Point2d p = ps[i];
sascha@593:             if (p != null) {
sascha@593:                 double di = distance(p);
sascha@593:                 if (di < 1e-5d) { z = p.z; return; }
sascha@593:                 di = 1d/di;
sascha@593:                 d[i] = di;
sascha@593:                 sum += di;
sascha@593:             }
sascha@593:         }
sascha@593: 
sascha@593:         if (sum == 0d) {
sascha@593:             return;
sascha@593:         }
sascha@593: 
sascha@593:         double v = 0d;
sascha@593: 
sascha@593:         for (int i = 0; i < ps.length; ++i) {
sascha@593:             Point2d p = ps[i];
sascha@593:             if (p != null) {
sascha@593:                 v += p.z*d[i];
sascha@593:             }
sascha@593:         }
sascha@593:         z = v/sum;
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Creates a new point via {@link #newPoint() } with the
sascha@798:      * x,y coordinates of the center of a given set of
sascha@798:      * coordinates.
sascha@798:      * @param ps The points from which the x,y coordinates are
sascha@798:      * taken to calculate the center.
sascha@798:      * @return The new center point.
sascha@798:      */
sascha@593:     public static Point2d average(Point2d [] ps) {
sascha@593: 
sascha@593:         Point2d p = null;
sascha@593:         int count = 0;
sascha@593: 
sascha@593:         for (int i = 0; i < ps.length; ++i) {
sascha@593:             Point2d t = ps[i];
sascha@593:             if (t != null) {
sascha@593:                 ++count;
sascha@593:                 if (p == null) {
sascha@593:                     p = t.newPoint(t.x, t.y);
sascha@593:                 }
sascha@593:                 else {
sascha@593:                     p.x += t.x;
sascha@593:                     p.y += t.y;
sascha@593:                 }
sascha@593:             }
sascha@593:         }
sascha@593: 
sascha@593:         if (p != null) {
sascha@593:             double s = 1d/count;
sascha@593:             p.x *= s;
sascha@593:             p.y *= s;
sascha@593:         }
sascha@593: 
sascha@593:         return p;
sascha@593:     }
sascha@593: 
sascha@798:     /**
sascha@798:      * Checks if this Point2d is near to at least one point
sascha@798:      * out of a given set of points. Near is defined by an
sascha@798:      * euclidian distance small than {@link #EPSILON}.
sascha@798:      * @param ps The set of points to be tested.
sascha@798:      * @return true if this Point2d is near to one of the given
sascha@798:      * points, else false.
sascha@798:      */
sascha@593:     public boolean near(Point2d [] ps) {
sascha@593: 
sascha@593:         for (int i = 0; i < ps.length; ++i) {
sascha@593:             Point2d p = ps[i];
sascha@593:             if (p != null && distance(p) > EPSILON) {
sascha@593:                 return false;
sascha@593:             }
sascha@593:         }
sascha@593: 
sascha@593:         return true;
sascha@593:     }
sascha@361: }
sascha@798: // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :