Add create points along methods to linestring and multilinestring

Author: jericks

src/main/groovy/geoscript/geom/LineString.groovy

@@ -2,6 +2,7 @@ package geoscript.geom
 
 import org.locationtech.jts.geom.LineString as JtsLineString
 import org.locationtech.jts.geom.Coordinate
+import org.locationtech.jts.linearref.LengthIndexedLine
 
 /**
  * A LineString Geometry.
@@ -236,6 +237,24 @@ class LineString extends Geometry {
         Geometry.wrap(indexedLine.extractLine(start * length, end * length))
     }
 
+    /**
+     * Create Points along the LineString with the given interval distance.
+     * @param distance The interval distance of distance between points.
+     * @return A MultiPoint
+     */
+    MultiPoint createPointsAlong(double distance) {
+        LengthIndexedLine lengthIndexedLine = new LengthIndexedLine(this.g)
+        List<Point> points = []
+        points.add(this.startPoint)
+        double distanceAlongLine = distance
+        while (distanceAlongLine < this.length) {
+            Coordinate coordinate = lengthIndexedLine.extractPoint(distanceAlongLine)
+            points.add(new Point(coordinate.x, coordinate.y))
+            distanceAlongLine = distanceAlongLine + distance
+        }
+        new MultiPoint(points)
+    }
+
     /**
      * Create a LineString from a List of List of Doubles.
      * <p><blockquote><pre>

src/main/groovy/geoscript/geom/MultiLineString.groovy

@@ -142,6 +142,30 @@ class MultiLineString extends GeometryCollection {
         results
     }
 
+    /**
+     * Create Points along this MultiLineString with the given interval distance.
+     * @param distance The interval distance of distance between points.
+     * @return A MultiPoint
+     */
+    MultiPoint createPointsAlong(double distance) {
+        createPointsAlongGeometry(this, distance)
+    }
+
+    private MultiPoint createPointsAlongGeometry(Geometry geometry, double distance) {
+        List<Point> points = []
+        geometry.geometries.each { Geometry subGeometry ->
+            if (subGeometry instanceof MultiLineString) {
+                MultiLineString multiLineString = subGeometry as MultiLineString
+                points.addAll(createPointsAlongGeometry(multiLineString, distance).points)
+            } else if (subGeometry instanceof LineString) {
+                LineString lineString = subGeometry as LineString
+                points.addAll(lineString.createPointsAlong(distance).points)
+            }
+        }
+        new MultiPoint(points)
+    }
+
+
     /**
      * Create a MultiLineString from a List of List of Doubles
      */

src/test/groovy/geoscript/geom/LineStringTestCase.groovy

@@ -135,6 +135,16 @@ class LineStringTestCase {
         assertEquals "LINESTRING (1156010.153864557 649246.3016361536, 1175115.6870342216 648021.5879714314)", subLine.wkt
     }
 
+    @Test void createPointsAlong() {
+        def line = new LineString([
+            [1137466.548141059, 650434.9943107369],
+            [1175272.4129268457, 648011.541439853],
+            [1185935.6055587344, 632986.1336403737]
+        ])
+        MultiPoint points = line.createPointsAlong(2000)
+        assertEquals(29, points.numGeometries)
+    }
+
     @Test void addPoint() {
         def line = new LineString([new Point(0,0), new Point(5,5)])
         def newLine = line.addPoint(1, new Point(3,3))

src/test/groovy/geoscript/geom/MultiLineStringTestCase.groovy

@@ -85,4 +85,15 @@ class MultiLineStringTestCase {
         assertTrue results.invalidRingLines.empty
     }
 
+    @Test void createPointsAlong() {
+        def lines = new MultiLineString(
+                new LineString ([-5.70068359375, 45.1416015625], [2.47314453125, 53.9306640625]),
+                new LineString ([-1.21826171875, 53.9306640625], [8.88916015625, 46.1962890625]),
+                new LineString ([0.71533203125, 42.63671875], [7.13134765625, 50.37109375]),
+                new LineString ([-5.83251953125, 46.943359375], [4.45068359375, 42.98828125])
+        )
+        MultiPoint points = lines.createPointsAlong(1)
+        assertEquals(49, points.numGeometries)
+    }
+
 }