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Java example source code file (Line.java)

This example Java source code file (Line.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, default_tolerance, deprecated, euclidean1d, geometry, hyperplane, line, linetransform, mathillegalargumentexception, orientedpoint, point, polygonsset, subhyperplane, subline, vector1d, vector2d

The Line.java Java example source code

/*
 * 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.awt.geom.AffineTransform;

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.Vector;
import org.apache.commons.math3.geometry.euclidean.oned.Euclidean1D;
import org.apache.commons.math3.geometry.euclidean.oned.IntervalsSet;
import org.apache.commons.math3.geometry.euclidean.oned.OrientedPoint;
import org.apache.commons.math3.geometry.euclidean.oned.Vector1D;
import org.apache.commons.math3.geometry.partitioning.Embedding;
import org.apache.commons.math3.geometry.partitioning.Hyperplane;
import org.apache.commons.math3.geometry.partitioning.SubHyperplane;
import org.apache.commons.math3.geometry.partitioning.Transform;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathArrays;
import org.apache.commons.math3.util.MathUtils;

/** This class represents an oriented line in the 2D plane.

 * <p>An oriented line can be defined either by prolongating a line
 * segment between two points past these points, or by one point and
 * an angular direction (in trigonometric orientation).</p>

 * <p>Since it is oriented the two half planes at its two sides are
 * unambiguously identified as a left half plane and a right half
 * plane. This can be used to identify the interior and the exterior
 * in a simple way by local properties only when part of a line is
 * used to define part of a polygon boundary.</p>

 * <p>A line can also be used to completely define a reference frame
 * in the plane. It is sufficient to select one specific point in the
 * line (the orthogonal projection of the original reference frame on
 * the line) and to use the unit vector in the line direction and the
 * orthogonal vector oriented from left half plane to right half
 * plane. We define two coordinates by the process, the
 * <em>abscissa along the line, and the offset across
 * the line. All points of the plane are uniquely identified by these
 * two coordinates. The line is the set of points at zero offset, the
 * left half plane is the set of points with negative offsets and the
 * right half plane is the set of points with positive offsets.</p>

 * @since 3.0
 */
public class Line implements Hyperplane<Euclidean2D>, Embedding {

    /** Default value for tolerance. */
    private static final double DEFAULT_TOLERANCE = 1.0e-10;

    /** Angle with respect to the abscissa axis. */
    private double angle;

    /** Cosine of the line angle. */
    private double cos;

    /** Sine of the line angle. */
    private double sin;

    /** Offset of the frame origin. */
    private double originOffset;

    /** Tolerance below which points are considered identical. */
    private final double tolerance;

    /** Reverse line. */
    private Line reverse;

    /** Build a line from two points.
     * <p>The line is oriented from p1 to p2

* @param p1 first point * @param p2 second point * @param tolerance tolerance below which points are considered identical * @since 3.3 */ public Line(final Vector2D p1, final Vector2D p2, final double tolerance) { reset(p1, p2); this.tolerance = tolerance; } /** Build a line from a point and an angle. * @param p point belonging to the line * @param angle angle of the line with respect to abscissa axis * @param tolerance tolerance below which points are considered identical * @since 3.3 */ public Line(final Vector2D p, final double angle, final double tolerance) { reset(p, angle); this.tolerance = tolerance; } /** Build a line from its internal characteristics. * @param angle angle of the line with respect to abscissa axis * @param cos cosine of the angle * @param sin sine of the angle * @param originOffset offset of the origin * @param tolerance tolerance below which points are considered identical * @since 3.3 */ private Line(final double angle, final double cos, final double sin, final double originOffset, final double tolerance) { this.angle = angle; this.cos = cos; this.sin = sin; this.originOffset = originOffset; this.tolerance = tolerance; this.reverse = null; } /** Build a line from two points. * <p>The line is oriented from p1 to p2

* @param p1 first point * @param p2 second point * @deprecated as of 3.3, replaced with {@link #Line(Vector2D, Vector2D, double)} */ @Deprecated public Line(final Vector2D p1, final Vector2D p2) { this(p1, p2, DEFAULT_TOLERANCE); } /** Build a line from a point and an angle. * @param p point belonging to the line * @param angle angle of the line with respect to abscissa axis * @deprecated as of 3.3, replaced with {@link #Line(Vector2D, double, double)} */ @Deprecated public Line(final Vector2D p, final double angle) { this(p, angle, DEFAULT_TOLERANCE); } /** Copy constructor. * <p>The created instance is completely independent from the * original instance, it is a deep copy.</p> * @param line line to copy */ public Line(final Line line) { angle = MathUtils.normalizeAngle(line.angle, FastMath.PI); cos = line.cos; sin = line.sin; originOffset = line.originOffset; tolerance = line.tolerance; reverse = null; } /** {@inheritDoc} */ public Line copySelf() { return new Line(this); } /** Reset the instance as if built from two points. * <p>The line is oriented from p1 to p2

* @param p1 first point * @param p2 second point */ public void reset(final Vector2D p1, final Vector2D p2) { unlinkReverse(); final double dx = p2.getX() - p1.getX(); final double dy = p2.getY() - p1.getY(); final double d = FastMath.hypot(dx, dy); if (d == 0.0) { angle = 0.0; cos = 1.0; sin = 0.0; originOffset = p1.getY(); } else { angle = FastMath.PI + FastMath.atan2(-dy, -dx); cos = dx / d; sin = dy / d; originOffset = MathArrays.linearCombination(p2.getX(), p1.getY(), -p1.getX(), p2.getY()) / d; } } /** Reset the instance as if built from a line and an angle. * @param p point belonging to the line * @param alpha angle of the line with respect to abscissa axis */ public void reset(final Vector2D p, final double alpha) { unlinkReverse(); this.angle = MathUtils.normalizeAngle(alpha, FastMath.PI); cos = FastMath.cos(this.angle); sin = FastMath.sin(this.angle); originOffset = MathArrays.linearCombination(cos, p.getY(), -sin, p.getX()); } /** Revert the instance. */ public void revertSelf() { unlinkReverse(); if (angle < FastMath.PI) { angle += FastMath.PI; } else { angle -= FastMath.PI; } cos = -cos; sin = -sin; originOffset = -originOffset; } /** Unset the link between an instance and its reverse. */ private void unlinkReverse() { if (reverse != null) { reverse.reverse = null; } reverse = null; } /** Get the reverse of the instance. * <p>Get a line with reversed orientation with respect to the * instance.</p> * <p> * As long as neither the instance nor its reverse are modified * (i.e. as long as none of the {@link #reset(Vector2D, Vector2D)}, * {@link #reset(Vector2D, double)}, {@link #revertSelf()}, * {@link #setAngle(double)} or {@link #setOriginOffset(double)} * methods are called), then the line and its reverse remain linked * together so that {@code line.getReverse().getReverse() == line}. * When one of the line is modified, the link is deleted as both * instance becomes independent. * </p> * @return a new line, with orientation opposite to the instance orientation */ public Line getReverse() { if (reverse == null) { reverse = new Line((angle < FastMath.PI) ? (angle + FastMath.PI) : (angle - FastMath.PI), -cos, -sin, -originOffset, tolerance); reverse.reverse = this; } return reverse; } /** Transform a space point into a sub-space point. * @param vector n-dimension point of the space * @return (n-1)-dimension point of the sub-space corresponding to * the specified space point */ public Vector1D toSubSpace(Vector<Euclidean2D> vector) { return toSubSpace((Point<Euclidean2D>) vector); } /** Transform a sub-space point into a space point. * @param vector (n-1)-dimension point of the sub-space * @return n-dimension point of the space corresponding to the * specified sub-space point */ public Vector2D toSpace(Vector<Euclidean1D> vector) { return toSpace((Point<Euclidean1D>) vector); } /** {@inheritDoc} */ public Vector1D toSubSpace(final Point<Euclidean2D> point) { Vector2D p2 = (Vector2D) point; return new Vector1D(MathArrays.linearCombination(cos, p2.getX(), sin, p2.getY())); } /** {@inheritDoc} */ public Vector2D toSpace(final Point<Euclidean1D> point) { final double abscissa = ((Vector1D) point).getX(); return new Vector2D(MathArrays.linearCombination(abscissa, cos, -originOffset, sin), MathArrays.linearCombination(abscissa, sin, originOffset, cos)); } /** Get the intersection point of the instance and another line. * @param other other line * @return intersection point of the instance and the other line * or null if there are no intersection points */ public Vector2D intersection(final Line other) { final double d = MathArrays.linearCombination(sin, other.cos, -other.sin, cos); if (FastMath.abs(d) < tolerance) { return null; } return new Vector2D(MathArrays.linearCombination(cos, other.originOffset, -other.cos, originOffset) / d, MathArrays.linearCombination(sin, other.originOffset, -other.sin, originOffset) / d); } /** {@inheritDoc} * @since 3.3 */ public Point<Euclidean2D> project(Point point) { return toSpace(toSubSpace(point)); } /** {@inheritDoc} * @since 3.3 */ public double getTolerance() { return tolerance; } /** {@inheritDoc} */ public SubLine wholeHyperplane() { return new SubLine(this, new IntervalsSet(tolerance)); } /** Build a region covering the whole space. * @return a region containing the instance (really a {@link * PolygonsSet PolygonsSet} instance) */ public PolygonsSet wholeSpace() { return new PolygonsSet(tolerance); } /** Get the offset (oriented distance) of a parallel line. * <p>This method should be called only for parallel lines otherwise * the result is not meaningful.</p> * <p>The offset is 0 if both lines are the same, it is * positive if the line is on the right side of the instance and * negative if it is on the left side, according to its natural * orientation.</p> * @param line line to check * @return offset of the line */ public double getOffset(final Line line) { return originOffset + (MathArrays.linearCombination(cos, line.cos, sin, line.sin) > 0 ? -line.originOffset : line.originOffset); } /** Get the offset (oriented distance) of a vector. * @param vector vector to check * @return offset of the vector */ public double getOffset(Vector<Euclidean2D> vector) { return getOffset((Point<Euclidean2D>) vector); } /** {@inheritDoc} */ public double getOffset(final Point<Euclidean2D> point) { Vector2D p2 = (Vector2D) point; return MathArrays.linearCombination(sin, p2.getX(), -cos, p2.getY(), 1.0, originOffset); } /** {@inheritDoc} */ public boolean sameOrientationAs(final Hyperplane<Euclidean2D> other) { final Line otherL = (Line) other; return MathArrays.linearCombination(sin, otherL.sin, cos, otherL.cos) >= 0.0; } /** Get one point from the plane. * @param abscissa desired abscissa for the point * @param offset desired offset for the point * @return one point in the plane, with given abscissa and offset * relative to the line */ public Vector2D getPointAt(final Vector1D abscissa, final double offset) { final double x = abscissa.getX(); final double dOffset = offset - originOffset; return new Vector2D(MathArrays.linearCombination(x, cos, dOffset, sin), MathArrays.linearCombination(x, sin, -dOffset, cos)); } /** Check if the line contains a point. * @param p point to check * @return true if p belongs to the line */ public boolean contains(final Vector2D p) { return FastMath.abs(getOffset(p)) < tolerance; } /** Compute the distance between the instance and a point. * <p>This is a shortcut for invoking FastMath.abs(getOffset(p)), * and provides consistency with what is in the * org.apache.commons.math3.geometry.euclidean.threed.Line class.</p> * * @param p to check * @return distance between the instance and the point * @since 3.1 */ public double distance(final Vector2D p) { return FastMath.abs(getOffset(p)); } /** Check the instance is parallel to another line. * @param line other line to check * @return true if the instance is parallel to the other line * (they can have either the same or opposite orientations) */ public boolean isParallelTo(final Line line) { return FastMath.abs(MathArrays.linearCombination(sin, line.cos, -cos, line.sin)) < tolerance; } /** Translate the line to force it passing by a point. * @param p point by which the line should pass */ public void translateToPoint(final Vector2D p) { originOffset = MathArrays.linearCombination(cos, p.getY(), -sin, p.getX()); } /** Get the angle of the line. * @return the angle of the line with respect to the abscissa axis */ public double getAngle() { return MathUtils.normalizeAngle(angle, FastMath.PI); } /** Set the angle of the line. * @param angle new angle of the line with respect to the abscissa axis */ public void setAngle(final double angle) { unlinkReverse(); this.angle = MathUtils.normalizeAngle(angle, FastMath.PI); cos = FastMath.cos(this.angle); sin = FastMath.sin(this.angle); } /** Get the offset of the origin. * @return the offset of the origin */ public double getOriginOffset() { return originOffset; } /** Set the offset of the origin. * @param offset offset of the origin */ public void setOriginOffset(final double offset) { unlinkReverse(); originOffset = offset; } /** Get a {@link org.apache.commons.math3.geometry.partitioning.Transform * Transform} embedding an affine transform. * @param transform affine transform to embed (must be inversible * otherwise the {@link * org.apache.commons.math3.geometry.partitioning.Transform#apply(Hyperplane) * apply(Hyperplane)} method would work only for some lines, and * fail for other ones) * @return a new transform that can be applied to either {@link * Vector2D Vector2D}, {@link Line Line} or {@link * org.apache.commons.math3.geometry.partitioning.SubHyperplane * SubHyperplane} instances * @exception MathIllegalArgumentException if the transform is non invertible * @deprecated as of 3.6, replaced with {@link #getTransform(double, double, double, double, double, double)} */ @Deprecated public static Transform<Euclidean2D, Euclidean1D> getTransform(final AffineTransform transform) throws MathIllegalArgumentException { final double[] m = new double[6]; transform.getMatrix(m); return new LineTransform(m[0], m[1], m[2], m[3], m[4], m[5]); } /** Get a {@link org.apache.commons.math3.geometry.partitioning.Transform * Transform} embedding an affine transform. * @param cXX transform factor between input abscissa and output abscissa * @param cYX transform factor between input abscissa and output ordinate * @param cXY transform factor between input ordinate and output abscissa * @param cYY transform factor between input ordinate and output ordinate * @param cX1 transform addendum for output abscissa * @param cY1 transform addendum for output ordinate * @return a new transform that can be applied to either {@link * Vector2D Vector2D}, {@link Line Line} or {@link * org.apache.commons.math3.geometry.partitioning.SubHyperplane * SubHyperplane} instances * @exception MathIllegalArgumentException if the transform is non invertible * @since 3.6 */ public static Transform<Euclidean2D, Euclidean1D> getTransform(final double cXX, final double cYX, final double cXY, final double cYY, final double cX1, final double cY1) throws MathIllegalArgumentException { return new LineTransform(cXX, cYX, cXY, cYY, cX1, cY1); } /** Class embedding an affine transform. * <p>This class is used in order to apply an affine transform to a * line. Using a specific object allow to perform some computations * on the transform only once even if the same transform is to be * applied to a large number of lines (for example to a large * polygon)./<p> */ private static class LineTransform implements Transform<Euclidean2D, Euclidean1D> { /** Transform factor between input abscissa and output abscissa. */ private double cXX; /** Transform factor between input abscissa and output ordinate. */ private double cYX; /** Transform factor between input ordinate and output abscissa. */ private double cXY; /** Transform factor between input ordinate and output ordinate. */ private double cYY; /** Transform addendum for output abscissa. */ private double cX1; /** Transform addendum for output ordinate. */ private double cY1; /** cXY * cY1 - cYY * cX1. */ private double c1Y; /** cXX * cY1 - cYX * cX1. */ private double c1X; /** cXX * cYY - cYX * cXY. */ private double c11; /** Build an affine line transform from a n {@code AffineTransform}. * @param cXX transform factor between input abscissa and output abscissa * @param cYX transform factor between input abscissa and output ordinate * @param cXY transform factor between input ordinate and output abscissa * @param cYY transform factor between input ordinate and output ordinate * @param cX1 transform addendum for output abscissa * @param cY1 transform addendum for output ordinate * @exception MathIllegalArgumentException if the transform is non invertible * @since 3.6 */ LineTransform(final double cXX, final double cYX, final double cXY, final double cYY, final double cX1, final double cY1) throws MathIllegalArgumentException { this.cXX = cXX; this.cYX = cYX; this.cXY = cXY; this.cYY = cYY; this.cX1 = cX1; this.cY1 = cY1; c1Y = MathArrays.linearCombination(cXY, cY1, -cYY, cX1); c1X = MathArrays.linearCombination(cXX, cY1, -cYX, cX1); c11 = MathArrays.linearCombination(cXX, cYY, -cYX, cXY); if (FastMath.abs(c11) < 1.0e-20) { throw new MathIllegalArgumentException(LocalizedFormats.NON_INVERTIBLE_TRANSFORM); } } /** {@inheritDoc} */ public Vector2D apply(final Point<Euclidean2D> point) { final Vector2D p2D = (Vector2D) point; final double x = p2D.getX(); final double y = p2D.getY(); return new Vector2D(MathArrays.linearCombination(cXX, x, cXY, y, cX1, 1), MathArrays.linearCombination(cYX, x, cYY, y, cY1, 1)); } /** {@inheritDoc} */ public Line apply(final Hyperplane<Euclidean2D> hyperplane) { final Line line = (Line) hyperplane; final double rOffset = MathArrays.linearCombination(c1X, line.cos, c1Y, line.sin, c11, line.originOffset); final double rCos = MathArrays.linearCombination(cXX, line.cos, cXY, line.sin); final double rSin = MathArrays.linearCombination(cYX, line.cos, cYY, line.sin); final double inv = 1.0 / FastMath.sqrt(rSin * rSin + rCos * rCos); return new Line(FastMath.PI + FastMath.atan2(-rSin, -rCos), inv * rCos, inv * rSin, inv * rOffset, line.tolerance); } /** {@inheritDoc} */ public SubHyperplane<Euclidean1D> apply(final SubHyperplane sub, final Hyperplane<Euclidean2D> original, final Hyperplane<Euclidean2D> transformed) { final OrientedPoint op = (OrientedPoint) sub.getHyperplane(); final Line originalLine = (Line) original; final Line transformedLine = (Line) transformed; final Vector1D newLoc = transformedLine.toSubSpace(apply(originalLine.toSpace(op.getLocation()))); return new OrientedPoint(newLoc, op.isDirect(), originalLine.tolerance).wholeHyperplane(); } } }

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