Polygon2d.java
package org.djutils.draw.line;
import java.awt.geom.Path2D;
import java.awt.geom.Path2D.Double;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import org.djutils.draw.bounds.Bounds2d;
import org.djutils.draw.point.Point2d;
import org.djutils.exceptions.Throw;
/**
* Closed PolyLine2d. The actual closing point (which is the same as the starting point) is NOT included in the super
* PolyLine2d. The constructors automatically remove the last point if it is a at the same location as the first point.
* <p>
* Copyright (c) 2020-2025 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
* BSD-style license. See <a href="https://djutils.org/docs/current/djutils/licenses.html">DJUTILS License</a>.
* </p>
* @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
* @author <a href="https://github.com/peter-knoppers">Peter Knoppers</a>
* @author <a href="https://github.com/wjschakel">Wouter Schakel</a>
*/
public class Polygon2d extends PolyLine2d
{
/** */
private static final long serialVersionUID = 20209999L;
/**
* Construct a new Polygon2d.
* @param x the x coordinates of the points
* @param y the y coordinates of the points
* @throws NullPointerException when <code>x</code>, or <code>y</code> is <code>null</code>
* @throws IllegalArgumentException when any two successive points are equal, or when there are too few points, or when the
* lengths of the coordinate arrays are not equal
*/
public Polygon2d(final double[] x, final double[] y)
{
this(NO_FILTER, x, y);
}
/**
* Construct a new Polygon2d.
* @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
* @param x the x coordinates of the points
* @param y the y coordinates of the points
* @throws NullPointerException when <code>x</code>, or <code>y</code> is <code>null</code>
* @throws IllegalArgumentException when any two successive points are equal, or when there are too few points, or when the
* lengths of the coordinate arrays are not equal
*/
public Polygon2d(final double epsilon, final double[] x, final double[] y)
{
super(epsilon, fixClosingPoint(Throw.whenNull(x, "x"), Throw.whenNull(y, "y")), fixClosingPoint(y, x));
}
/**
* Ensure that the last pair of values in two arrays are not equal to the first pair. Remove the last pair if necessary.
* @param a the a array
* @param b the b array
* @return the <code>a</code> array (possibly a copy with the last element removed)
*/
private static double[] fixClosingPoint(final double[] a, final double[] b)
{
if (a.length > 1 && b.length == a.length && a[0] == a[a.length - 1] && b[0] == b[a.length - 1])
{
return Arrays.copyOf(a, a.length - 1);
}
return a;
}
/**
* Construct a new Polygon2d.
* @param points array of Point2d objects.
* @throws NullPointerException when <code>points</code> is <code>null</code>
* @throws IllegalArgumentException when <code>points</code> is too short, or contains successive duplicate points
*/
public Polygon2d(final Point2d[] points)
{
this(NO_FILTER, points);
}
/**
* Construct a new Polygon2d.
* @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
* @param points array of Point2d objects.
* @throws NullPointerException when <code>points</code> is <code>null</code>
* @throws IllegalArgumentException when <code>points</code> is too short, or contains successive duplicate points
*/
public Polygon2d(final double epsilon, final Point2d[] points)
{
this(epsilon, PolyLine2d.makeArray(points, p -> p.x), PolyLine2d.makeArray(points, p -> p.y));
}
/**
* Construct a new Polygon2d.
* @param point1 the first point of the new Polygon2d
* @param point2 the second point of the new Polygon2d
* @param otherPoints all remaining points of the new Polygon2d (may be <code>null</code>)
* @throws NullPointerException when <code>point1</code> or <code>point2</code> is <code>null</code>, or
* <code>otherPoints</code> contains a <code>null</code> value
* @throws IllegalArgumentException when <code>point1</code> is equal to the last entry of <code>otherPoints</code>, or any
* two successive points are equal
*/
public Polygon2d(final Point2d point1, final Point2d point2, final Point2d... otherPoints)
{
this(NO_FILTER, point1, point2, otherPoints);
}
/**
* Construct a new Polygon2d.
* @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
* @param point1 the first point of the new Polygon2d
* @param point2 the second point of the new Polygon2d
* @param otherPoints all remaining points of the new Polygon2d (may be <code>null</code>)
* @throws NullPointerException when <code>point1</code> or <code>point2</code> is <code>null</code>, or
* <code>otherPoints</code> contains a <code>null</code> value
* @throws IllegalArgumentException when <code>point1</code> is equal to the last entry of <code>otherPoints</code>, or any
* two successive points are equal
*/
public Polygon2d(final double epsilon, final Point2d point1, final Point2d point2, final Point2d... otherPoints)
{
super(epsilon, Throw.whenNull(point1, "point1"), Throw.whenNull(point2, "point2"),
fixClosingPoint(point1, otherPoints));
}
/**
* Ensure that the last point of otherPoints is not equal to point1. Remove the last point if necessary.
* @param point1 the first point of a new Polygon2d
* @param otherPoints the remaining points of a new Polygon2d (may be <code>null</code>)
* @return <code>otherPoints</code> (possibly a copy thereof with the last entry removed)
*/
private static Point2d[] fixClosingPoint(final Point2d point1, final Point2d[] otherPoints)
{
if (otherPoints == null || otherPoints.length == 0)
{
return otherPoints;
}
Point2d[] result = otherPoints;
Point2d lastPoint = result[result.length - 1];
if (point1.x == lastPoint.x && point1.y == lastPoint.y)
{
result = Arrays.copyOf(otherPoints, result.length - 1);
lastPoint = result[result.length - 1];
}
Throw.when(point1.x == lastPoint.x && point1.y == lastPoint.y, IllegalArgumentException.class,
"Before last point and last point are at same location");
return result;
}
/**
* Construct a new Polygon2d from a list of Point2d objects.
* @param points the list of points
* @throws NullPointerException when <code>points</code> is <code>null</code>, or contains a <code>null</code> value
* @throws IllegalArgumentException when <code>points</code> is too short, or the last two points are at the same location
*/
public Polygon2d(final List<Point2d> points)
{
this(NO_FILTER, points);
}
/**
* Construct a new Polygon2d from a list of Point2d objects.
* @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
* @param points the list of points
* @throws NullPointerException when <code>points</code> is <code>null</code>, or contains a <code>null</code> value
* @throws IllegalArgumentException when <code>points</code> is too short, or the last two points are at the same location
*/
public Polygon2d(final double epsilon, final List<Point2d> points)
{
super(epsilon, fixClosingPoint(true, Throw.whenNull(points, "points")));
}
/**
* Ensure that the last point in the list is different from the first point by possibly removing the last point.
* @param doNotModifyList if <code>true</code>; the list of points will not be modified (if the last point is to be
* removed; the entire list up to the last point is duplicated)
* @param points the list of points
* @return the fixed list
* @throws NullPointerException when <code>points</code> is <code>null</code>
* @throws IllegalArgumentException when the (resulting) list is too short, or the before last and last point of points have
* the same coordinates
*/
private static List<Point2d> fixClosingPoint(final boolean doNotModifyList, final List<Point2d> points)
{
Throw.when(points.size() < 2, IllegalArgumentException.class, "Need at least two points");
Point2d firstPoint = points.get(0);
Point2d lastPoint = points.get(points.size() - 1);
List<Point2d> result = points;
if (firstPoint.x == lastPoint.x && firstPoint.y == lastPoint.y)
{
if (doNotModifyList)
{
result = new ArrayList<>(points.size() - 1);
for (int i = 0; i < points.size() - 1; i++)
{
result.add(points.get(i));
}
}
else
{
result.remove(points.size() - 1);
}
lastPoint = result.get(result.size() - 1);
}
Throw.when(firstPoint.x == lastPoint.x && firstPoint.y == lastPoint.y, IllegalArgumentException.class,
"Before last point and last point are at same location");
return result;
}
/**
* Construct a new Polygon2d from an iterator that yields Point2d.
* @param iterator the iterator
* @throws NullPointerException when <code>iterator</code> is <code>null</code>, or the iterator returns a <code>null</code>
* value
* @throws IllegalArgumentException when the <code>iterator</code> yields too few points, or the before last and last point
* have the same coordinates
*/
public Polygon2d(final Iterator<Point2d> iterator)
{
this(NO_FILTER, iterator);
}
/**
* Construct a new Polygon2d from an iterator that yields Point2d.
* @param epsilon minimum distance between points to be considered different (these will <b>not</b> be filtered out)
* @param iterator the iterator
* @throws NullPointerException when <code>iterator</code> is <code>null</code>, or the iterator returns a <code>null</code>
* value
* @throws IllegalArgumentException when the <code>iterator</code> yields too few points, or the before last and last point
* have the same coordinates
*/
public Polygon2d(final double epsilon, final Iterator<Point2d> iterator)
{
this(epsilon, fixClosingPoint(false, iteratorToList(Throw.whenNull(iterator, "iterator"))));
}
/**
* Construct a new Polygon2d from an existing one. This constructor is primarily intended for use in extending classes.
* @param polygon the existing Polygon2d
* @throws NullPointerException when <code>polygon</code> is <code>null</code>
*/
public Polygon2d(final Polygon2d polygon)
{
super(polygon);
}
/**
* Determine if this Polygon is convex. Returns bogus result for self-intersecting polygons. Derived from
* <a href="http://paulbourke.net/geometry/polygonmesh/source2.c">Convex by Paul Bourke</a>
* @return <code>true</code> if this <code>Polygon2d</code> is convex; <code>false</code> if this
* <code>Polygon2d</code> is concave
*/
public final boolean isConvex()
{
int flag = 0;
for (int i = 0; i < size(); i++)
{
int j = (i + 1) % size();
int k = (j + 1) % size();
double z = (getX(j) - getX(i)) * (getY(k) - getY(j)) - (getY(j) - getY(i)) * (getX(k) - getX(j));
if (z < 0)
{
flag |= 1;
}
else if (z > 0)
{
flag |= 2;
}
if (flag == 3)
{
return false;
}
}
return flag != 0;
}
/**
* Determine if a point is inside this Polygon. Returns bogus results for self-intersecting polygons.
* @param point the point
* @return <code>true</code> if the point is inside this <code>Polygon2d</code>, <code>false</code> if the point is
* outside this <code>Polygon2d</code>. Results are ill-defined for points on the edges of this
* <code>Polygon2d</code>.
*/
public boolean contains(final Point2d point)
{
return contains(point.x, point.y);
}
/**
* Determine if a point is inside this Polygon. Returns bogus results for self-intersecting polygons. Derived from
* <a href="http://paulbourke.net/geometry/polygonmesh/">Polygons and meshes by Paul Bourke</a>
* @param x the x-coordinate of the point
* @param y the y-coordinate of the point
* @return <code>true</code> if the point is inside this <code>Polygon2d</code>, <code>false</code> if the point is
* outside this <code>Polygon2d</code>. Results are ill-defined for points on the edges of this
* <code>Polygon2d</code>.
*/
public boolean contains(final double x, final double y)
{
if (!getBounds().contains(x, y))
{
return false;
}
int counter = 0;
// Unlike Paul Bourke, we initialize prevPoint to the last point of the polygon (so we never have to wrap around)
double prevPointX = getX(size() - 1);
double prevPointY = getY(size() - 1);
for (int i = 0; i < size(); i++)
{
double curPointX = getX(i);
double curPointY = getY(i);
// Combined 4 if statements into one; I trust that the java compiler will short-circuit this nicely
if (y > Math.min(prevPointY, curPointY) && y <= Math.max(prevPointY, curPointY)
&& x <= Math.max(prevPointX, curPointX) && prevPointY != curPointY)
{
double xIntersection = (y - prevPointY) * (curPointX - prevPointX) / (curPointY - prevPointY) + prevPointX;
if (prevPointX == curPointX || x <= xIntersection)
{
counter++;
}
}
prevPointX = curPointX;
prevPointY = curPointY;
}
return counter % 2 != 0;
}
/**
* Determine if this Polygon completely contains a Bounds2d object. If this Polygon self-intersects, the results is bogus.
* @param bounds the Bounds2d object
* @return <code>true</code> if the <code>Bounds2d</code> object is completely contained in this
* <code>Polygon2d</code>; <code>false</code> if any part (or all) of the Bounds2d object is outside this
* <code>Polygon2d</code>. If the Bounds2d object touches this <code>Polygon2d</code> the results are ill-defined.
*/
public boolean contains(final Bounds2d bounds)
{
// Step 1: quick check to see if the bounds intersect
if (getBounds().disjoint(bounds))
{
return false;
}
// This is a quick hack
return toPath2D().contains(bounds.getMinX(), bounds.getMinY(), bounds.getDeltaX(), bounds.getDeltaY());
}
/**
* Determine if this Polygon2d intersects another Polygon2d.
* @param other the other Polygon2d
* @return <code>true</code> if the polygons intersect; <code>false</code> if the polygons are disjunct.
* Ill-defined if the polygons touch.
*/
public boolean intersects(final Polygon2d other)
{
// step 1: quick check to see if the bounds intersect
if (!getBounds().intersects(other.getBounds()))
{
return false;
}
// step 2: quick check to see if any of the points of this polygon lies inside the other polygon
for (Iterator<Point2d> iterator = iterator(); iterator.hasNext();)
{
if (other.contains(iterator.next()))
{
return true;
}
}
// step 3: quick check to see if any of the points of the other polygon lies inside this polygon
for (Iterator<Point2d> iterator = other.iterator(); iterator.hasNext();)
{
if (contains(iterator.next()))
{
return true;
}
}
// step 4: see if any of the lines of shape 1 and shape 2 intersect (expensive!)
for (int i = 0; i < this.size(); i++)
{
LineSegment2d ourSegment = getSegment(i);
for (int j = 0; j < other.size(); j++)
{
LineSegment2d otherSegment = other.getSegment(j);
Point2d intersection = Point2d.intersectionOfLineSegments(ourSegment, otherSegment);
if (intersection != null)
{
double p1x = ourSegment.startX, p1y = ourSegment.startY;
double d1x = ourSegment.endX - p1x, d1y = ourSegment.endY - p1y;
double p2x = otherSegment.startX, p2y = otherSegment.startY;
double d2x = otherSegment.endX - p2x, d2y = otherSegment.endY - p2y;
double det = d2x * d1y - d2y * d1x;
if (det != 0)
{
double z = (d2x * (p2y - p1y) + d2y * (p1x - p2x)) / det;
if (Math.abs(z) < 10.0 * Math.ulp(1.0) || Math.abs(z - 1.0) > 10.0 * Math.ulp(1.0))
{
return true; // intersection at end point
}
}
}
}
}
return false;
}
/**
* Compute the surface of this Polygon2d. Sign of the result reflects the winding-ness of this this Polygon2d. If this
* Polygon2d self-intersects, the result is bogus.
* @return the surface of this <code>Polygon2d</code>
*/
public double surface()
{
// Translate all coordinates to the median of the bounding box to minimize rounding errors
Point2d midPoint = getBounds().midPoint();
double result = 0;
// We initialize previous point to the last point of this Polygon2d to avoid wrapping problems
double prevX = getX(size() - 1) - midPoint.x;
double prevY = getY(size() - 1) - midPoint.y;
for (int i = 0; i < size(); i++)
{
double thisX = getX(i) - midPoint.x;
double thisY = getY(i) - midPoint.y;
result += prevX * thisY - thisX * prevY;
prevX = thisX;
prevY = thisY;
}
return result / 2;
}
@Override
public double getLength()
{
// Length of a polygon is computed by taking the length of the PolyLine and adding the length of the closing segment
return super.getLength() + Math.hypot(getX(size() - 1) - getX(0), getY(size() - 1) - getY(0));
}
@Override
public LineSegment2d getSegment(final int index)
{
if (index < size() - 1)
{
return super.getSegment(index);
}
Throw.when(index != size() - 1, IndexOutOfBoundsException.class, "index must be in range [0..size() - 1] (got %d)",
index);
return new LineSegment2d(getX(index), getY(index), getX(0), getY(0));
}
@Override
public Polygon2d reverse()
{
return new Polygon2d(super.reverse().iterator());
}
/**
* Construct a Path2D from this PolyLine2d. The result is NOT cached (in the current implementation).
* @return newly construct Path2D consisting solely of straight segments.
*/
@Override
public Path2D toPath2D()
{
Path2D.Double result = (Double) super.toPath2D();
result.closePath();
return result;
}
@Override
public final String toString()
{
return toString("%f", false);
}
@Override
public String toString(final String doubleFormat, final boolean doNotIncludeClassName)
{
StringBuilder result = new StringBuilder();
if (!doNotIncludeClassName)
{
result.append("Polygon2d ");
}
result.append("[super=");
result.append(super.toString(doubleFormat, false));
result.append("]");
return result.toString();
}
}