Addd TestBuilder metric functions

Author: dr-jts

modules/app/src/main/java/org/locationtech/jtstest/function/MetricFunctions.java

@@ -0,0 +1,87 @@
+/*
+ * Copyright (c) 2025 Martin Davis.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
+ * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
+ * and the Eclipse Distribution License is available at
+ *
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ */
+package org.locationtech.jtstest.function;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.CoordinateSequence;
+import org.locationtech.jts.geom.CoordinateSequenceFilter;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jtstest.geomfunction.Metadata;
+
+public class MetricFunctions {
+  
+  /**
+   * Returns a line graph of segment lengths.
+   * Graph is scaled to maximum segment length.
+   * 
+   * @param geom geometry to sample
+   * @param numSamples number of points in line graph
+   * @return line graph of segment lengths
+   */
+  public static Geometry segmentLengths(final Geometry geom, 
+      @Metadata(title="# of samples")
+      int numSamples) {
+    
+    if (numSamples < 1)
+      numSamples = 1;
+    
+    List<Double> segLen = new ArrayList<Double>();
+    CoordinateSequenceFilter segLenFilter = new CoordinateSequenceFilter() {
+
+      @Override
+      public void filter(CoordinateSequence seq, int i) {
+        if (i == 0) {
+          segLen.add(0.0);
+          return;
+        }
+        Coordinate p0 = seq.getCoordinate(i);
+        Coordinate p1 = seq.getCoordinate(i-1);
+        double len = p0.distance(p1);
+        segLen.add(len);
+      }
+
+      @Override
+      public boolean isDone() {
+        return false;
+      }
+
+      @Override
+      public boolean isGeometryChanged() {
+        return false;
+      }
+      
+    };
+    geom.apply(segLenFilter);
+    Collections.sort(segLen);
+    
+    double maxLen = segLen.get(segLen.size() - 1);
+    Coordinate[] pts = new Coordinate[numSamples + 1];
+    int breakSize = segLen.size() / numSamples + 1;
+    double dx = maxLen / numSamples;
+    for (int i = 0; i < numSamples + 1; i++) {
+      
+      double x = (i >= numSamples) ? maxLen : i * dx;
+      
+      int sampleIndex = i * breakSize; 
+      if (sampleIndex >= segLen.size())
+        sampleIndex = segLen.size() - 1;
+      double y = segLen.get(sampleIndex);
+      pts[i] = new Coordinate(x, y);
+    }
+    
+    return geom.getFactory().createLineString(pts);
+  }
+}

modules/app/src/main/java/org/locationtech/jtstest/geomfunction/GeometryFunctionRegistry.java

@@ -43,6 +43,7 @@
 import org.locationtech.jtstest.function.LineHandlingFunctions;
 import org.locationtech.jtstest.function.LineSegmentFunctions;
 import org.locationtech.jtstest.function.LinearReferencingFunctions;
+import org.locationtech.jtstest.function.MetricFunctions;
 import org.locationtech.jtstest.function.NodingFunctions;
 import org.locationtech.jtstest.function.OffsetCurveFunctions;
 import org.locationtech.jtstest.function.OrientationFPFunctions;
@@ -100,6 +101,7 @@ public static GeometryFunctionRegistry createTestBuilderRegistry()
     funcRegistry.add(HullFunctions.class);
     funcRegistry.add(LinearReferencingFunctions.class);
     funcRegistry.add(LineHandlingFunctions.class);
+    funcRegistry.add(MetricFunctions.class);
     funcRegistry.add(NodingFunctions.class);
     funcRegistry.add(PolygonizeFunctions.class);
     funcRegistry.add(PrecisionFunctions.class);