Vector2D.java
/*
* Copyright (c) 2016 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.math;
import org.locationtech.jts.algorithm.Angle;
import org.locationtech.jts.algorithm.CGAlgorithmsDD;
import org.locationtech.jts.geom.Coordinate;
import org.locationtech.jts.util.Assert;
/**
* A 2-dimensional mathematical vector represented by double-precision X and Y components.
*
* @author mbdavis
*
*/
public class Vector2D {
/**
* Creates a new vector with given X and Y components.
*
* @param x the x component
* @param y the y component
* @return a new vector
*/
public static Vector2D create(double x, double y) {
return new Vector2D(x, y);
}
/**
* Creates a new vector from an existing one.
*
* @param v the vector to copy
* @return a new vector
*/
public static Vector2D create(Vector2D v) {
return new Vector2D(v);
}
/**
* Creates a vector from a {@link Coordinate}.
*
* @param coord the Coordinate to copy
* @return a new vector
*/
public static Vector2D create(Coordinate coord) {
return new Vector2D(coord);
}
/**
* Creates a vector with the direction and magnitude
* of the difference between the
* <tt>to</tt> and <tt>from</tt> {@link Coordinate}s.
*
* @param from the origin Coordinate
* @param to the destination Coordinate
* @return a new vector
*/
public static Vector2D create(Coordinate from, Coordinate to) {
return new Vector2D(from, to);
}
/**
* The X component of this vector.
*/
private double x;
/**
* The Y component of this vector.
*/
private double y;
public Vector2D() {
this(0.0, 0.0);
}
public Vector2D(double x, double y) {
this.x = x;
this.y = y;
}
public Vector2D(Vector2D v) {
x = v.x;
y = v.y;
}
public Vector2D(Coordinate from, Coordinate to) {
x = to.x - from.x;
y = to.y - from.y;
}
public Vector2D(Coordinate v) {
x = v.x;
y = v.y;
}
public double getX() {
return x;
}
public double getY() {
return y;
}
public double getComponent(int index) {
if (index == 0)
return x;
return y;
}
public Vector2D add(Vector2D v) {
return create(x + v.x, y + v.y);
}
public Vector2D subtract(Vector2D v) {
return create(x - v.x, y - v.y);
}
/**
* Multiplies the vector by a scalar value.
*
* @param d the value to multiply by
* @return a new vector with the value v * d
*/
public Vector2D multiply(double d) {
return create(x * d, y * d);
}
/**
* Divides the vector by a scalar value.
*
* @param d the value to divide by
* @return a new vector with the value v / d
*/
public Vector2D divide(double d) {
return create(x / d, y / d);
}
public Vector2D negate() {
return create(-x , -y);
}
public double length() {
return Math.hypot(x, y);
}
public double lengthSquared() {
return x * x + y * y;
}
public Vector2D normalize() {
double length = length();
if (length > 0.0)
return divide(length);
return create(0.0, 0.0);
}
public Vector2D average(Vector2D v) {
return weightedSum(v, 0.5);
}
/**
* Computes the weighted sum of this vector
* with another vector,
* with this vector contributing a fraction
* of <tt>frac</tt> to the total.
* <p>
* In other words,
* <pre>
* sum = frac * this + (1 - frac) * v
* </pre>
*
* @param v the vector to sum
* @param frac the fraction of the total contributed by this vector
* @return the weighted sum of the two vectors
*/
public Vector2D weightedSum(Vector2D v, double frac) {
return create(
frac * x + (1.0 - frac) * v.x,
frac * y + (1.0 - frac) * v.y);
}
/**
* Computes the distance between this vector and another one.
* @param v a vector
* @return the distance between the vectors
*/
public double distance(Vector2D v)
{
double delx = v.x - x;
double dely = v.y - y;
return Math.hypot(delx, dely);
}
/**
* Computes the dot-product of two vectors
*
* @param v a vector
* @return the dot product of the vectors
*/
public double dot(Vector2D v) {
return x * v.x + y * v.y;
}
public double angle()
{
return Math.atan2(y, x);
}
public double angle(Vector2D v)
{
return Angle.diff(v.angle(), angle());
}
public double angleTo(Vector2D v)
{
double a1 = angle();
double a2 = v.angle();
double angDel = a2 - a1;
// normalize, maintaining orientation
if (angDel <= -Math.PI)
return angDel + Angle.PI_TIMES_2;
if (angDel > Math.PI)
return angDel - Angle.PI_TIMES_2;
return angDel;
}
public Vector2D rotate(double angle)
{
double cos = Math.cos(angle);
double sin = Math.sin(angle);
return create(
x * cos - y * sin,
x * sin + y * cos
);
}
/**
* Rotates a vector by a given number of quarter-circles (i.e. multiples of 90
* degrees or Pi/2 radians). A positive number rotates counter-clockwise, a
* negative number rotates clockwise. Under this operation the magnitude of
* the vector and the absolute values of the ordinates do not change, only
* their sign and ordinate index.
*
* @param numQuarters
* the number of quarter-circles to rotate by
* @return the rotated vector.
*/
public Vector2D rotateByQuarterCircle(int numQuarters) {
int nQuad = numQuarters % 4;
if (numQuarters < 0 && nQuad != 0) {
nQuad = nQuad + 4;
}
switch (nQuad) {
case 0:
return create(x, y);
case 1:
return create(-y, x);
case 2:
return create(-x, -y);
case 3:
return create(y, -x);
}
Assert.shouldNeverReachHere();
return null;
}
public boolean isParallel(Vector2D v)
{
return 0.0 == CGAlgorithmsDD.signOfDet2x2(x, y, v.x, v.y);
}
public Coordinate translate(Coordinate coord) {
return new Coordinate(x + coord.x, y + coord.y);
}
public Coordinate toCoordinate() {
return new Coordinate(x, y);
}
/**
* Creates a copy of this vector
*
* @return a copy of this vector
*/
public Object clone()
{
return new Vector2D(this);
}
/**
* Gets a string representation of this vector
*
* @return a string representing this vector
*/
public String toString() {
return "[" + x + ", " + y + "]";
}
/**
* Tests if a vector <tt>o</tt> has the same values for the x and y
* components.
*
* @param o
* a <tt>Vector2D</tt> with which to do the comparison.
* @return true if <tt>other</tt> is a <tt>Vector2D</tt> with the same
* values for the x and y components.
*/
public boolean equals(Object o) {
if (!(o instanceof Vector2D)) {
return false;
}
Vector2D v = (Vector2D) o;
return x == v.x && y == v.y;
}
/**
* Gets a hashcode for this vector.
*
* @return a hashcode for this vector
*/
public int hashCode() {
// Algorithm from Effective Java by Joshua Bloch
int result = 17;
result = 37 * result + Coordinate.hashCode(x);
result = 37 * result + Coordinate.hashCode(y);
return result;
}
}