Improve CoverageSimplifier with ring removal, smoothing, inner/outer …

…and per-feature tolerances (#1060)

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

@@ -11,6 +11,7 @@
  */
 package org.locationtech.jtstest.function;
 
+import java.util.Arrays;
 import java.util.List;
 
 import org.locationtech.jts.coverage.CoverageGapFinder;
@@ -62,20 +63,82 @@ public static Geometry union(Geometry coverage) {
   public static Geometry simplify(Geometry coverage, double tolerance) {
     Geometry[] cov = toGeometryArray(coverage);
     Geometry[] result =  CoverageSimplifier.simplify(cov, tolerance);
-    return FunctionsUtil.buildGeometry(result);
+    return coverage.getFactory().createGeometryCollection(result);
+  }
+
+  @Metadata(description="Simplify a coverage with a smoothness weight")
+  public static Geometry simplifySharp(Geometry coverage, 
+      @Metadata(title="Distance tol")
+      double tolerance, 
+      @Metadata(title="Weight")
+      double weight) {
+    Geometry[] cov = toGeometryArray(coverage);
+    CoverageSimplifier simplifier = new CoverageSimplifier(cov);
+    simplifier.setSmoothWeight(weight);
+    Geometry[] result = simplifier.simplify(tolerance);
+    return coverage.getFactory().createGeometryCollection(result);
+  }
+
+  @Metadata(description="Simplify a coverage with a ring removal size factor")
+  public static Geometry simplifyRemoveRings(Geometry coverage, 
+      @Metadata(title="Distance tol")
+      double tolerance, 
+      @Metadata(title="Removal Size Factor")
+      double factor) {
+    Geometry[] cov = toGeometryArray(coverage);
+    CoverageSimplifier simplifier = new CoverageSimplifier(cov);
+    simplifier.setRemovableRingSizeFactor(factor);
+    Geometry[] result = simplifier.simplify(tolerance);
+    return coverage.getFactory().createGeometryCollection(result);
   }
 
   @Metadata(description="Simplify inner edges of a coverage")
-  public static Geometry simplifyinner(Geometry coverage, double tolerance) {
+  public static Geometry simplifyInner(Geometry coverage, double tolerance) {
     Geometry[] cov = toGeometryArray(coverage);
     Geometry[] result =  CoverageSimplifier.simplifyInner(cov, tolerance);
+    return coverage.getFactory().createGeometryCollection(result);
+  }
+
+  @Metadata(description="Simplify outer edges of a coverage")
+  public static Geometry simplifyOuter(Geometry coverage, double tolerance) {
+    Geometry[] cov = toGeometryArray(coverage);
+    Geometry[] result =  CoverageSimplifier.simplifyOuter(cov, tolerance);
+    return coverage.getFactory().createGeometryCollection(result);
+  }
+
+  @Metadata(description="Simplify inner and outer edges of a coverage differently")
+  public static Geometry simplifyInOut(Geometry coverage, 
+      @Metadata(title="Inner Distance tol")
+      double toleranceInner, 
+      @Metadata(title="Outer Distance tol")
+      double toleranceOuter) {
+    Geometry[] cov = toGeometryArray(coverage);
+    CoverageSimplifier simplifier = new CoverageSimplifier(cov);
+    Geometry[] result = simplifier.simplify(toleranceInner, toleranceOuter);
+    return coverage.getFactory().createGeometryCollection(result);
+  }
+
+  @Metadata(description="Simplify a coverage with per-geometry tolerances")
+  public static Geometry simplifyTolerances(Geometry coverage, 
+      @Metadata(title="Tolerances (comma-sep)")
+      String tolerancesCSV) {
+    Geometry[] cov = toGeometryArray(coverage);
+    double[] tolerances = tolerances(tolerancesCSV, cov.length);
+    Geometry[] result =  CoverageSimplifier.simplify(cov, tolerances);
     return FunctionsUtil.buildGeometry(result);
   }
 
-  static Geometry extractPolygons(Geometry geom) {
-    List components = PolygonExtracter.getPolygons(geom);
-    Geometry result = geom.getFactory().buildGeometry(components);
-    return result;
+  private static double[] tolerances(String csvList, int len) {
+    Double[] tolsDouble = toDoubleArray(csvList);
+    double[] tols = new double[len];
+    for (int i = 0; i < tolsDouble.length; i++) {
+      tols[i] = tolsDouble[i];
+    }
+    return tols;
+  }  
+
+  private static Double[] toDoubleArray(String csvList) {
+    return Arrays.stream(csvList.split(",")).map(Double::parseDouble).toArray(Double[]::new);
   }
 
   private static Geometry[] toGeometryArray(Geometry geom) {

modules/core/src/main/java/org/locationtech/jts/coverage/Corner.java

@@ -25,12 +25,12 @@ class Corner implements Comparable<Corner> {
   private int next;
   private double area;
 
-  public Corner(LinkedLine edge, int i) {
+  public Corner(LinkedLine edge, int i, double area) {
     this.edge = edge;
     this.index = i; 
     this.prev = edge.prev(i);
     this.next = edge.next(i);
-    this.area = area(edge, i);
+    this.area = area;
   }
 
   public boolean isVertex(int index) {
@@ -58,13 +58,6 @@ public Coordinate prev() {
   public Coordinate next() {
     return edge.getCoordinate(next);  
   }
-
-  private static double area(LinkedLine edge, int index) {
-    Coordinate pp = edge.prevCoordinate(index);
-    Coordinate p = edge.getCoordinate(index);
-    Coordinate pn = edge.nextCoordinate(index);
-    return Triangle.area(pp, p, pn);
-  }
 
   /**
    * Orders corners by increasing area.

modules/core/src/main/java/org/locationtech/jts/coverage/CornerArea.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2022 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.jts.coverage;
+
+import org.locationtech.jts.algorithm.Angle;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Triangle;
+import org.locationtech.jts.math.MathUtil;
+
+/**
+ * Computes the effective area of corners, 
+ * taking into account the smoothing weight.
+ * 
+ * <h3>FUTURE WORK</h3>
+ * 
+ * Support computing geodetic area
+ * 
+ * @author Martin Davis
+ *
+ */
+class CornerArea {
+  public static final double DEFAULT_SMOOTH_WEIGHT = 0.0;
+
+  private double smoothWeight = DEFAULT_SMOOTH_WEIGHT;
+
+  public CornerArea() {
+  }
+
+  /**
+   * Creates a new corner area computer.
+   * 
+   * @param smoothWeight the weight for smoothing corners.  In range [0..1].
+   */
+  public CornerArea(double smoothWeight) {
+    this.smoothWeight = smoothWeight;
+  }
+
+  public double area(Coordinate pp, Coordinate p, Coordinate pn) {
+
+    double area = Triangle.area(pp, p, pn);
+    double ang = angleNorm(pp, p, pn);
+    //-- rescale to [-1 .. 1], with 1 being narrow and -1 being flat
+    double angBias = 1.0 - 2.0 * ang;
+    //-- reduce area for narrower corners, to make them more likely to be removed
+    double areaWeighted = (1 - smoothWeight * angBias) * area;
+    return areaWeighted;
+  }
+
+  private static double angleNorm(Coordinate pp, Coordinate p, Coordinate pn) {
+    double angNorm = Angle.angleBetween(pp, p, pn) / 2 / Math.PI;
+    return MathUtil.clamp(angNorm, 0, 1);
+  }
+}

modules/core/src/main/java/org/locationtech/jts/coverage/CoverageEdge.java

@@ -11,47 +11,38 @@
  */
 package org.locationtech.jts.coverage;
 
-import java.util.List;
-
 import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.CoordinateArrays;
 import org.locationtech.jts.geom.GeometryFactory;
 import org.locationtech.jts.geom.LineSegment;
 import org.locationtech.jts.geom.LineString;
-import org.locationtech.jts.geom.MultiLineString;
 import org.locationtech.jts.io.WKTWriter;
 
 /**
  * An edge of a polygonal coverage formed from all or a section of a polygon ring.
- * An edge may be a free ring, which is a ring which has not node points
- * (i.e. does not touch any other rings in the parent coverage).
+ * An edge may be a free ring, which is a ring which has no node points
+ * (i.e. does not share a vertex with any other rings in the parent coverage).
  * 
  * @author mdavis
  *
  */
 class CoverageEdge {
 
-  public static CoverageEdge createEdge(Coordinate[] ring) {
+  public static final int RING_COUNT_INNER = 2;
+  public static final int RING_COUNT_OUTER = 1;
+
+  public static CoverageEdge createEdge(Coordinate[] ring, boolean isPrimary) {
     Coordinate[] pts = extractEdgePoints(ring, 0, ring.length - 1);
-    CoverageEdge edge = new CoverageEdge(pts, true);
+    CoverageEdge edge = new CoverageEdge(pts, isPrimary, true);
     return edge;
   }
 
-  public static CoverageEdge createEdge(Coordinate[] ring, int start, int end) {
+  public static CoverageEdge createEdge(Coordinate[] ring, int start, int end, boolean isPrimary) {
     Coordinate[] pts = extractEdgePoints(ring, start, end);
-    CoverageEdge edge = new CoverageEdge(pts, false);
+    CoverageEdge edge = new CoverageEdge(pts, isPrimary, false);
     return edge;
   }
 
-  static MultiLineString createLines(List<CoverageEdge> edges, GeometryFactory geomFactory) {
-    LineString lines[] = new LineString[edges.size()];
-    for (int i = 0; i < edges.size(); i++) {
-      CoverageEdge edge = edges.get(i);
-      lines[i] = edge.toLineString(geomFactory);
-    }
-    MultiLineString mls = geomFactory.createMultiLineString(lines);
-    return mls;
-  }
-
   private static Coordinate[] extractEdgePoints(Coordinate[] ring, int start, int end) {
     int size = start < end 
                   ? end - start + 1 
@@ -136,12 +127,16 @@ else if (i > pts.length - 1) {
   private Coordinate[] pts;
   private int ringCount = 0;
   private boolean isFreeRing = true;
+  private boolean isPrimary = true;
+  private int adjacentIndex0 = -1;
+  private int adjacentIndex1 = -1;
 
-  public CoverageEdge(Coordinate[] pts, boolean isFreeRing) {
+  public CoverageEdge(Coordinate[] pts, boolean isPrimary, boolean isFreeRing) {
     this.pts = pts;
+    this.isPrimary = isPrimary;
     this.isFreeRing = isFreeRing;
   }
-
+  
   public void incRingCount() {
     ringCount++;
   }
@@ -150,9 +145,30 @@ public int getRingCount() {
     return ringCount;
   }
 
+  public boolean isInner() {
+    return ringCount == RING_COUNT_INNER;
+  }
+
+  public boolean isOuter() {
+    return ringCount == RING_COUNT_OUTER;
+  }
+
+  public void setPrimary(boolean isPrimary) {
+    //-- preserve primary status if set
+    if (this.isPrimary)
+      return;
+    this.isPrimary = isPrimary;
+  }
+
+  public boolean isRemovableRing() {
+    boolean isRing = CoordinateArrays.isRing(pts);
+    return isRing && ! isPrimary;
+  }
+
   /**
    * Returns whether this edge is a free ring;
-   * i.e. one with no constrained nodes.
+   * i.e. one that does not have nodes
+   * which are anchored because they occur in another ring.
    * 
    * @return true if this is a free ring
    */
@@ -184,5 +200,28 @@ public String toString() {
     return WKTWriter.toLineString(pts);
   }
 
+  public void addIndex(int index) {
+    //TODO: keep information about which element is L and R?
+
+    // assert: at least one elementIndex is unset (< 0)
+    if (adjacentIndex0 < 0) {
+      adjacentIndex0 = index;
+    }
+    else {
+      adjacentIndex1 = index;
+    }
+  }
+
+  public int getAdjacentIndex(int index) {
+    if (index == 0)
+      return adjacentIndex0;
+    return adjacentIndex1;
+  }
+
+  public boolean hasAdjacentIndex(int index) {
+    if (index == 0)
+      return adjacentIndex0 >= 0;
+    return adjacentIndex1 >= 0;
+  }
 
 }