| /* |
| * 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.geometry.euclidean.twod.hull; |
| |
| import java.util.Collection; |
| |
| import org.apache.commons.geometry.core.precision.DoublePrecisionContext; |
| import org.apache.commons.geometry.core.precision.EpsilonDoublePrecisionContext; |
| import org.apache.commons.geometry.euclidean.twod.Vector2D; |
| |
| /** |
| * Abstract base class for convex hull generators in the two-dimensional Euclidean space. |
| */ |
| abstract class AbstractConvexHullGenerator2D implements ConvexHullGenerator2D { |
| |
| /** Default epsilon value. */ |
| private static final double DEFAULT_EPSILON = 1e-10; |
| |
| /** Precision context used to compare floating point numbers. */ |
| private final DoublePrecisionContext precision; |
| |
| /** |
| * Indicates if collinear points on the hull shall be present in the output. |
| * If {@code false}, only the extreme points are added to the hull. |
| */ |
| private final boolean includeCollinearPoints; |
| |
| /** |
| * Simple constructor. |
| * <p> |
| * The default epsilon (1e-10) will be used to determine identical points. |
| * |
| * @param includeCollinearPoints indicates if collinear points on the hull shall be |
| * added as hull vertices |
| */ |
| protected AbstractConvexHullGenerator2D(final boolean includeCollinearPoints) { |
| this(includeCollinearPoints, new EpsilonDoublePrecisionContext(DEFAULT_EPSILON)); |
| } |
| |
| /** |
| * Simple constructor. |
| * |
| * @param includeCollinearPoints indicates if collinear points on the hull shall be |
| * added as hull vertices |
| * @param precision precision context used to compare floating point numbers |
| */ |
| protected AbstractConvexHullGenerator2D(final boolean includeCollinearPoints, |
| final DoublePrecisionContext precision) { |
| this.includeCollinearPoints = includeCollinearPoints; |
| this.precision = precision; |
| } |
| |
| /** Get the object used to determine floating point equality for this region. |
| * @return the floating point precision context for the instance |
| */ |
| public DoublePrecisionContext getPrecision() { |
| return precision; |
| } |
| |
| /** |
| * Returns if collinear points on the hull will be added as hull vertices. |
| * @return {@code true} if collinear points are added as hull vertices, or {@code false} |
| * if only extreme points are present. |
| */ |
| public boolean isIncludeCollinearPoints() { |
| return includeCollinearPoints; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public ConvexHull2D generate(final Collection<Vector2D> points) |
| throws IllegalStateException { |
| Collection<Vector2D> hullVertices = null; |
| if (points.size() < 2) { |
| hullVertices = points; |
| } else { |
| hullVertices = findHullVertices(points); |
| } |
| |
| try { |
| return new ConvexHull2D(hullVertices.toArray(new Vector2D[hullVertices.size()]), |
| precision); |
| } catch (IllegalArgumentException e) { |
| // the hull vertices may not form a convex hull if the tolerance value is to large |
| throw new IllegalStateException("Convex hull algorithm failed to generate solution", e); |
| } |
| } |
| |
| /** |
| * Find the convex hull vertices from the set of input points. |
| * @param points the set of input points |
| * @return the convex hull vertices in CCW winding |
| */ |
| protected abstract Collection<Vector2D> findHullVertices(Collection<Vector2D> points); |
| |
| } |