Mercurial > dive4elements > gnv-client
comparison gnv-artifacts/src/main/java/de/intevation/gnv/math/L1Comparator.java @ 875:5e9efdda6894
merged gnv-artifacts/1.0
| author | Thomas Arendsen Hein <thomas@intevation.de> |
|---|---|
| date | Fri, 28 Sep 2012 12:13:56 +0200 (2012-09-28) |
| parents | a645bd23c1c8 |
| children | f953c9a559d8 |
comparison
equal
deleted
inserted
replaced
| 722:bb3ffe7d719e | 875:5e9efdda6894 |
|---|---|
| 1 package de.intevation.gnv.math; | |
| 2 | |
| 3 import com.vividsolutions.jts.geom.Coordinate; | |
| 4 | |
| 5 import java.util.Comparator; | |
| 6 | |
| 7 /** | |
| 8 * Compares two coordinates a and b by their L1(Manhattan) distance | |
| 9 * relative to a reference point r. | |
| 10 * da = L1(a, r)<br> | |
| 11 * db = L1(b, r)<br> | |
| 12 * -1 if da < db, +1 if da > db, 0 else. | |
| 13 * @author <a href="mailto:sascha.teichmann@intevation.de">Sascha L. Teichmann</a> | |
| 14 */ | |
| 15 public class L1Comparator | |
| 16 implements Comparator | |
| 17 { | |
| 18 private Coordinate ref; | |
| 19 | |
| 20 /** | |
| 21 * Default constructor. | |
| 22 */ | |
| 23 public L1Comparator() { | |
| 24 } | |
| 25 | |
| 26 /** | |
| 27 * Constructor to create a L1Comparator with a given reference point. | |
| 28 * @param ref The reference point. | |
| 29 */ | |
| 30 public L1Comparator(Coordinate ref) { | |
| 31 this.ref = ref; | |
| 32 } | |
| 33 | |
| 34 /** | |
| 35 * Explicitly sets the reference point. | |
| 36 * @param ref The reference point. | |
| 37 */ | |
| 38 public void setReference(Coordinate ref) { | |
| 39 this.ref = ref; | |
| 40 } | |
| 41 | |
| 42 /** | |
| 43 * Compares to coordinate by their L1 distance to the reference point. | |
| 44 * @param a The first coordinate. | |
| 45 * @param b The second coordinate. | |
| 46 * @return -1 if L1(a, ref) < L1(b, ref), | |
| 47 * +1 if L1(a, ref) > L1(b, ref), 0 else. | |
| 48 */ | |
| 49 public int compare(Object a, Object b) { | |
| 50 Coordinate pa = (Coordinate)a; | |
| 51 Coordinate pb = (Coordinate)b; | |
| 52 double da = L1(ref, pa); | |
| 53 double db = L1(ref, pb); | |
| 54 if (da < db) return -1; | |
| 55 if (da > db) return +1; | |
| 56 return 0; | |
| 57 } | |
| 58 | |
| 59 /** | |
| 60 * Computes the L1 distance between two points a and b:<br> | |
| 61 * L1(a, b) = abs(a.x - b.x) + abs(a.y - b.y) | |
| 62 * @param a The first point. | |
| 63 * @param b The second point. | |
| 64 * @return The L1 distance. | |
| 65 */ | |
| 66 public static double L1(Coordinate a, Coordinate b) { | |
| 67 return Math.abs(a.x - b.x) + Math.abs(a.y - b.y); | |
| 68 } | |
| 69 } | |
| 70 // vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 : |