Add TestBuilder truchetTiling function

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

@@ -19,6 +19,10 @@
 import org.locationtech.jts.geom.Envelope;
 import org.locationtech.jts.geom.Geometry;
 import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.geom.PrecisionModel;
+import org.locationtech.jts.geom.util.AffineTransformation;
+import org.locationtech.jts.operation.polygonize.Polygonizer;
+import org.locationtech.jts.precision.GeometryPrecisionReducer;
 import org.locationtech.jts.shape.random.RandomPointsBuilder;
 import org.locationtech.jts.shape.random.RandomPointsInGridBuilder;
 import org.locationtech.jtstest.geomfunction.Metadata;
@@ -354,4 +358,59 @@ private static Coordinate randomPtInRectangleAround(Coordinate centre, double wi
     return new Coordinate(x0, y0);    
   }
 
+  /**
+   * Truchet tiling created from a base (lower-left) tile defined by from set of lines.
+   * The tiles are copied to a square grid of size nSide,
+   * and rotated by a random multiple of 90 degrees.
+   * The tile line endpoints are snapped to a precision grid to make them align.
+   * If tiling is to be polygonized lines should be noded and snapped to edge points.
+   * 
+   * @param tileLines set of lines defining base tile
+   * @param nSide number of tiles per side of tiling
+   * @return lines for tiling.
+   */
+  @Metadata(description="Create Truchet tiling from lines defining lower left tile")
+  public static Geometry truchetTiling(Geometry tileLines, 
+      @Metadata(title="Grid side cell #")
+      int nSide) {
+    PrecisionModel pmSnap = new PrecisionModel(10000.0);
+    //Geometry tileSnap = snapEndpoints(tileLines.copy(), pmSnap);
+    Geometry tileSnap = GeometryPrecisionReducer.reduce(tileLines, pmSnap);
+    Envelope env = tileSnap.getEnvelopeInternal();
+    int side = (int) Math.max(env.getHeight(), env.getWidth());
+    Coordinate centre = env.centre();
+
+    List<Geometry> tiles = new ArrayList<Geometry>();
+    for (int i = 0; i < nSide; i++) {
+      for (int j = 0; j < nSide; j++) {
+        //-- random rotation by PI/2, translate to grid cell
+        int nPi2 = (int) (4 * Math.random());
+        AffineTransformation trans = AffineTransformation.rotationInstance(nPi2 * Math.PI / 2.0, 
+            centre.getX(), centre.getY());
+        trans.translate(i * side, j * side);
+
+        Geometry tileTrans = tileSnap.copy();
+        //-- don't transform base tile
+        if (i > 0 || j > 0) {
+          tileTrans.apply(trans);
+        }
+        //Geometry tileTransSnap = snapEndpoints(tileTrans, pmSnap);
+        Geometry tileTransSnap = GeometryPrecisionReducer.reduce(tileTrans, pmSnap);
+        tiles.add(tileTransSnap);
+      }
+    }
+    //-- close tiling and polygonize
+    double baseX = env.getMinX();
+    double baseY = env.getMinY();
+    Envelope tilingEnv = new Envelope(baseX, baseX + nSide * side, baseY, baseY + nSide * side); 
+    Geometry tilingBdy = tileLines.getFactory().toGeometry(tilingEnv).getBoundary();
+    tiles.add(tilingBdy);
+    Geometry tileLinesGeom = tileLines.getFactory().buildGeometry(tiles);
+    Geometry allLines = tileLinesGeom.union();
+    //System.out.println(allLines);
+    Polygonizer polygonizer = new Polygonizer();
+    polygonizer.add(allLines);
+    return polygonizer.getGeometry();
+  }
+
 }