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With inspiration from other libraries
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.geometry.euclidean.twod;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.geometry.Point;
import org.apache.commons.math3.geometry.euclidean.oned.IntervalsSet;
import org.apache.commons.math3.geometry.partitioning.Region;
import org.apache.commons.math3.geometry.partitioning.RegionFactory;
import org.apache.commons.math3.geometry.partitioning.SubHyperplane;
/** This class represent a tree of nested 2D boundary loops.
* This class is used for piecewise polygons construction.
* Polygons are built using the outline edges as
* representative of boundaries, the orientation of these lines are
* meaningful. However, we want to allow the user to specify its
* outline loops without having to take care of this orientation. This
* class is devoted to correct mis-oriented loops.
*
Orientation is computed assuming the piecewise polygon is finite,
* i.e. the outermost loops have their exterior side facing points at
* infinity, and hence are oriented counter-clockwise. The orientation of
* internal loops is computed as the reverse of the orientation of
* their immediate surrounding loop.
* @since 3.0
*/
class NestedLoops {
/** Boundary loop. */
private Vector2D[] loop;
/** Surrounded loops. */
private List surrounded;
/** Polygon enclosing a finite region. */
private Region polygon;
/** Indicator for original loop orientation. */
private boolean originalIsClockwise;
/** Tolerance below which points are considered identical. */
private final double tolerance;
/** Simple Constructor.
* Build an empty tree of nested loops. This instance will become
* the root node of a complete tree, it is not associated with any
* loop by itself, the outermost loops are in the root tree child
* nodes.
* @param tolerance tolerance below which points are considered identical
* @since 3.3
*/
NestedLoops(final double tolerance) {
this.surrounded = new ArrayList();
this.tolerance = tolerance;
}
/** Constructor.
* Build a tree node with neither parent nor children
* @param loop boundary loop (will be reversed in place if needed)
* @param tolerance tolerance below which points are considered identical
* @exception MathIllegalArgumentException if an outline has an open boundary loop
* @since 3.3
*/
private NestedLoops(final Vector2D[] loop, final double tolerance)
throws MathIllegalArgumentException {
if (loop[0] == null) {
throw new MathIllegalArgumentException(LocalizedFormats.OUTLINE_BOUNDARY_LOOP_OPEN);
}
this.loop = loop;
this.surrounded = new ArrayList();
this.tolerance = tolerance;
// build the polygon defined by the loop
final ArrayList> edges = new ArrayList>();
Vector2D current = loop[loop.length - 1];
for (int i = 0; i < loop.length; ++i) {
final Vector2D previous = current;
current = loop[i];
final Line line = new Line(previous, current, tolerance);
final IntervalsSet region =
new IntervalsSet(line.toSubSpace((Point) previous).getX(),
line.toSubSpace((Point) current).getX(),
tolerance);
edges.add(new SubLine(line, region));
}
polygon = new PolygonsSet(edges, tolerance);
// ensure the polygon encloses a finite region of the plane
if (Double.isInfinite(polygon.getSize())) {
polygon = new RegionFactory().getComplement(polygon);
originalIsClockwise = false;
} else {
originalIsClockwise = true;
}
}
/** Add a loop in a tree.
* @param bLoop boundary loop (will be reversed in place if needed)
* @exception MathIllegalArgumentException if an outline has crossing
* boundary loops or open boundary loops
*/
public void add(final Vector2D[] bLoop) throws MathIllegalArgumentException {
add(new NestedLoops(bLoop, tolerance));
}
/** Add a loop in a tree.
* @param node boundary loop (will be reversed in place if needed)
* @exception MathIllegalArgumentException if an outline has boundary
* loops that cross each other
*/
private void add(final NestedLoops node) throws MathIllegalArgumentException {
// check if we can go deeper in the tree
for (final NestedLoops child : surrounded) {
if (child.polygon.contains(node.polygon)) {
child.add(node);
return;
}
}
// check if we can absorb some of the instance children
for (final Iterator iterator = surrounded.iterator(); iterator.hasNext();) {
final NestedLoops child = iterator.next();
if (node.polygon.contains(child.polygon)) {
node.surrounded.add(child);
iterator.remove();
}
}
// we should be separate from the remaining children
RegionFactory factory = new RegionFactory();
for (final NestedLoops child : surrounded) {
if (!factory.intersection(node.polygon, child.polygon).isEmpty()) {
throw new MathIllegalArgumentException(LocalizedFormats.CROSSING_BOUNDARY_LOOPS);
}
}
surrounded.add(node);
}
/** Correct the orientation of the loops contained in the tree.
* This is this method that really inverts the loops that where
* provided through the {@link #add(Vector2D[]) add} method if
* they are mis-oriented
*/
public void correctOrientation() {
for (NestedLoops child : surrounded) {
child.setClockWise(true);
}
}
/** Set the loop orientation.
* @param clockwise if true, the loop should be set to clockwise
* orientation
*/
private void setClockWise(final boolean clockwise) {
if (originalIsClockwise ^ clockwise) {
// we need to inverse the original loop
int min = -1;
int max = loop.length;
while (++min < --max) {
final Vector2D tmp = loop[min];
loop[min] = loop[max];
loop[max] = tmp;
}
}
// go deeper in the tree
for (final NestedLoops child : surrounded) {
child.setClockWise(!clockwise);
}
}
}