Add PointLocation.isOnSegment function (#1048)

modules/core/src/main/java/org/locationtech/jts/algorithm/CGAlgorithms.java

@@ -179,12 +179,10 @@ public static int locatePointInRing(Coordinate p, Coordinate[] ring)
    */
   public static boolean isOnLine(Coordinate p, Coordinate[] pt)
   {
-    LineIntersector lineIntersector = new RobustLineIntersector();
     for (int i = 1; i < pt.length; i++) {
       Coordinate p0 = pt[i - 1];
       Coordinate p1 = pt[i];
-      lineIntersector.computeIntersection(p, p0, p1);
-      if (lineIntersector.hasIntersection()) {
+      if (PointLocation.isOnSegment(p, p0, p1)) {
         return true;
       }
     }

modules/core/src/main/java/org/locationtech/jts/algorithm/PointLocation.java

@@ -13,17 +13,37 @@
 
 import org.locationtech.jts.geom.Coordinate;
 import org.locationtech.jts.geom.CoordinateSequence;
+import org.locationtech.jts.geom.Envelope;
 import org.locationtech.jts.geom.Location;
 
 /**
  * Functions for locating points within basic geometric
- * structures such as lines and rings.
+ * structures such as line segments, lines and rings.
  * 
  * @author Martin Davis
  *
  */
 public class PointLocation {
 
+  /**
+   * Tests whether a point lies on a line segment.
+   * 
+   * @param p the point to test
+   * @param p0 a point of the line segment
+   * @param p1 a point of the line segment
+   * @return true if the point lies on the line segment
+   */
+  public static boolean isOnSegment(Coordinate p, Coordinate p0, Coordinate p1) {
+    //-- test envelope first since it's faster
+    if (! Envelope.intersects(p0, p1, p))
+      return false;
+    //-- handle zero-length segments
+    if (p.equals2D(p0))
+      return true;
+    boolean isOnLine = Orientation.COLLINEAR == Orientation.index(p0, p1, p);
+    return isOnLine;
+  }
+
   /**
    * Tests whether a point lies on the line defined by a list of
    * coordinates.
@@ -35,12 +55,10 @@ public class PointLocation {
    */
   public static boolean isOnLine(Coordinate p, Coordinate[] line)
   {
-    LineIntersector lineIntersector = new RobustLineIntersector();
     for (int i = 1; i < line.length; i++) {
       Coordinate p0 = line[i - 1];
       Coordinate p1 = line[i];
-      lineIntersector.computeIntersection(p, p0, p1);
-      if (lineIntersector.hasIntersection()) {
+      if (isOnSegment(p, p0, p1)) {
         return true;
       }
     }
@@ -58,15 +76,13 @@ public static boolean isOnLine(Coordinate p, Coordinate[] line)
    */
   public static boolean isOnLine(Coordinate p, CoordinateSequence line)
   {
-    LineIntersector lineIntersector = new RobustLineIntersector();
     Coordinate p0 = new Coordinate();
     Coordinate p1 = new Coordinate();
     int n = line.size();
     for (int i = 1; i < n; i++) {
       line.getCoordinate(i-1, p0);
       line.getCoordinate(i, p1);
-      lineIntersector.computeIntersection(p, p0, p1);
-      if (lineIntersector.hasIntersection()) {
+      if (isOnSegment(p, p0, p1)) {
         return true;
       }
     }

modules/core/src/main/java/org/locationtech/jts/operation/valid/PolygonTopologyAnalyzer.java

@@ -14,16 +14,15 @@
 import java.util.ArrayList;
 import java.util.List;
 
-import org.locationtech.jts.algorithm.LineIntersector;
 import org.locationtech.jts.algorithm.Orientation;
 import org.locationtech.jts.algorithm.PointLocation;
 import org.locationtech.jts.algorithm.PolygonNodeTopology;
-import org.locationtech.jts.algorithm.RobustLineIntersector;
 import org.locationtech.jts.geom.Coordinate;
 import org.locationtech.jts.geom.CoordinateArrays;
 import org.locationtech.jts.geom.Geometry;
 import org.locationtech.jts.geom.LinearRing;
 import org.locationtech.jts.geom.Location;
+import org.locationtech.jts.geom.MultiPolygon;
 import org.locationtech.jts.geom.Polygon;
 import org.locationtech.jts.noding.BasicSegmentString;
 import org.locationtech.jts.noding.MCIndexNoder;
@@ -185,10 +184,8 @@ private static int ringIndexNext(Coordinate[] ringPts, int index) {
    * @return the intersection segment index, or -1 if no intersection is found
    */
   private static int intersectingSegIndex(Coordinate[] ringPts, Coordinate pt) {
-    LineIntersector li = new RobustLineIntersector();
     for (int i = 0; i < ringPts.length - 1; i++) {
-      li.computeIntersection(pt, ringPts[i], ringPts[i + 1]);
-      if (li.hasIntersection()) {
+      if (PointLocation.isOnSegment(pt, ringPts[i], ringPts[i + 1])) {
         //-- check if pt is the start point of the next segment
         if (pt.equals2D(ringPts[i + 1])) {
           return i + 1;

modules/core/src/test/java/org/locationtech/jts/algorithm/PointLocationOnLineTest.java → modules/core/src/test/java/org/locationtech/jts/algorithm/PointLocationTest.java

@@ -12,34 +12,31 @@
 package org.locationtech.jts.algorithm;
 
 import org.locationtech.jts.geom.Coordinate;
-import org.locationtech.jts.geom.Geometry;
 import org.locationtech.jts.geom.LineString;
-import org.locationtech.jts.io.ParseException;
-import org.locationtech.jts.io.WKTReader;
 
-import junit.framework.TestCase;
 import junit.textui.TestRunner;
 import test.jts.GeometryTestCase;
 
 /**
- * Tests {@link PointLocation#isOnLine(Coordinate, Coordinate[])}.
+ * Tests {@link PointLocation}.
  * 
  * @version 1.15
  */
-public class PointLocationOnLineTest extends GeometryTestCase {
+public class PointLocationTest extends GeometryTestCase {
+
   public static void main(String args[]) {
-    TestRunner.run(PointLocationOnLineTest.class);
+    TestRunner.run(PointLocationTest.class);
   }
 
-  public PointLocationOnLineTest(String name) {
+  public PointLocationTest(String name) {
     super(name);
   }
 
-  public void testOnVertex() throws Exception {
+  public void testOnLineOnVertex() throws Exception {
     checkOnLine(20, 20, "LINESTRING (0 00, 20 20, 30 30)", true);
   }
 
-  public void testOnSegment() throws Exception {
+  public void testOnLineInSegment() throws Exception {
     checkOnLine(10, 10, "LINESTRING (0 0, 20 20, 0 40)", true);
     checkOnLine(10, 30, "LINESTRING (0 0, 20 20, 0 40)", true);
   }
@@ -48,6 +45,30 @@ public void testNotOnLine() throws Exception {
     checkOnLine(0, 100, "LINESTRING (10 10, 20 10, 30 10)", false);
   }
 
+  public void testOnSegment() {
+    checkOnSegment(5, 5, "LINESTRING(0 0, 9 9)", true);
+    checkOnSegment(0, 0, "LINESTRING(0 0, 9 9)", true);
+    checkOnSegment(9, 9, "LINESTRING(0 0, 9 9)", true);
+  }
+
+  public void testNotOnSegment() {
+    checkOnSegment(5, 6, "LINESTRING(0 0, 9 9)", false);
+    checkOnSegment(10, 10, "LINESTRING(0 0, 9 9)", false);
+    checkOnSegment(9, 9.00001, "LINESTRING(0 0, 9 9)", false);
+  }
+
+  public void testOnZeroLengthSegment() {
+    checkOnSegment(1, 1, "LINESTRING(1 1, 1 1)", true);
+    checkOnSegment(1, 2, "LINESTRING(1 1, 1 1)", false);
+  }
+
+  private void checkOnSegment(double x, double y, String wktLine, boolean expected) {
+    LineString line = (LineString) read(wktLine);
+    Coordinate p0 = line.getCoordinateN(0);
+    Coordinate p1 = line.getCoordinateN(1);
+    assertTrue(expected == PointLocation.isOnSegment(new Coordinate(x,y), p0, p1));
+  }
+
   void checkOnLine(double x, double y, String wktLine, boolean expected) {
     LineString line = (LineString) read(wktLine);
     assertTrue(expected == PointLocation.isOnLine(new Coordinate(x,y), line.getCoordinates()));