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Added distance to point to 2D Line and Segment. 

Patch provided by Curtis Jensen applied with minor modifications.

JIRA: MATH-641

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1392022 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Luc Maisonobe 2012-09-30 13:22:28 +00:00
parent 3246e42006
commit df92c3b6f1
6 changed files with 111 additions and 1 deletions
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3
pom.xml
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@ -192,6 +192,9 @@
<contributor> <contributor>
<name>Matthias Hummel</name> <name>Matthias Hummel</name>
</contributor> </contributor>
<contributor>
<name>Curtis Jensen</name>
</contributor>
<contributor> <contributor>
<name>Ismael Juma</name> <name>Ismael Juma</name>
</contributor> </contributor>

3
src/changes/changes.xml
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@ -52,6 +52,9 @@ If the output is not quite correct, check for invisible trailing spaces!
<body> <body>
<release version="3.1" date="TBD" description=" <release version="3.1" date="TBD" description="
"> ">
<action dev="luc" type="fix" issue="MATH-641" due-to="Curtis Jensen">
Added distance to point to 2D Line and Segment.
</action>
<action dev="erans" type="fix" issue="MATH-783"> <action dev="erans" type="fix" issue="MATH-783">
"PowellOptimizer" (package "o.a.c.m.optimization.direct") uses "PowellOptimizer" (package "o.a.c.m.optimization.direct") uses
"BrentOptimizer" as its internal line search optimizer. The fix "BrentOptimizer" as its internal line search optimizer. The fix

12
src/main/java/org/apache/commons/math3/geometry/euclidean/twod/Line.java
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@ -263,6 +263,18 @@ public class Line implements Hyperplane<Euclidean2D>, Embedding<Euclidean2D, Euc
return FastMath.abs(getOffset(p)) < 1.0e-10; return FastMath.abs(getOffset(p)) < 1.0e-10;
} }
/** Compute the distance between the instance and a point.
* 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.
*
* @param p to check
* @return distance between the instance and the point
*/
public double distance(final Vector2D p) {
return FastMath.abs(getOffset(p));
}
/** Check the instance is parallel to another line. /** Check the instance is parallel to another line.
* @param line other line to check * @param line other line to check
* @return true if the instance is parallel to the other line * @return true if the instance is parallel to the other line

40
src/main/java/org/apache/commons/math3/geometry/euclidean/twod/Segment.java
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@ -16,6 +16,7 @@
*/ */
package org.apache.commons.math3.geometry.euclidean.twod; package org.apache.commons.math3.geometry.euclidean.twod;
import org.apache.commons.math3.util.FastMath;
/** Simple container for a two-points segment. /** Simple container for a two-points segment.
* @version $Id$ * @version $Id$
@ -64,4 +65,43 @@ public class Segment {
return line; return line;
} }
/**
* Calculates the shortest distance from a point to this line segment.
* <p>
* If the perpendicular extension from the point to the line does not
* cross in the bounds of the line segment, the shortest distance to
* the two end points will be returned.
* </p>
*
* Algorithm adapted from: http://www.codeguru.com/forum/printthread.php?s=cc8cf0596231f9a7dba4da6e77c29db3&t=194400&pp=15&page=1
*/
public double distance(final Vector2D p) {
final double deltaX = end.getX() - start.getX();
final double deltaY = end.getY() - start.getY();
final double r = ((p.getX() - start.getX()) * deltaX + (p.getY() - start.getY()) * deltaY) /
(deltaX * deltaX + deltaY * deltaY);
// r == 0 => P = startPt
// r == 1 => P = endPt
// r < 0 => P is on the backward extension of the segment
// r > 1 => P is on the forward extension of the segment
// 0 < r < 1 => P is on the segment
// if point isn't on the line segment, just return the shortest distance to the end points
if (r < 0 || r > 1) {
final double dist1 = getStart().distance(p);
final double dist2 = getEnd().distance(p);
return FastMath.min(dist1, dist2);
}
else {
// find point on line and see if it is in the line segment
final double px = start.getX() + r * deltaX;
final double py = start.getY() + r * deltaY;
final Vector2D interPt = new Vector2D(px, py);
return interPt.distance(p);
}
}
} }

7
src/test/java/org/apache/commons/math3/geometry/euclidean/twod/LineTest.java
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@ -63,6 +63,13 @@ public class LineTest {
Assert.assertEquals(+5.0, l.getOffset(new Vector2D(-5, 2)), 1.0e-10); Assert.assertEquals(+5.0, l.getOffset(new Vector2D(-5, 2)), 1.0e-10);
} }
@Test
public void testDistance() {
Line l = new Line(new Vector2D(2, 1), new Vector2D(-2, -2));
Assert.assertEquals(+5.0, l.distance(new Vector2D(5, -3)), 1.0e-10);
Assert.assertEquals(+5.0, l.distance(new Vector2D(-5, 2)), 1.0e-10);
}
@Test @Test
public void testPointAt() { public void testPointAt() {
Line l = new Line(new Vector2D(2, 1), new Vector2D(-2, -2)); Line l = new Line(new Vector2D(2, 1), new Vector2D(-2, -2));

45
src/test/java/org/apache/commons/math3/geometry/euclidean/twod/SegmentTest.java Normal file
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@ -0,0 +1,45 @@
/*
* 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 org.apache.commons.math3.geometry.euclidean.twod.Line;
import org.apache.commons.math3.geometry.euclidean.twod.Vector2D;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;
import org.junit.Test;
public class SegmentTest {
@Test
public void testDistance() {
Vector2D start = new Vector2D(2, 2);
Vector2D end = new Vector2D(-2, -2);
Segment segment = new Segment(start, end, new Line(start, end));
// distance to center of segment
Assert.assertEquals(FastMath.sqrt(2), segment.distance(new Vector2D(1, -1)), 1.0e-10);
// distance a point on segment
Assert.assertEquals(FastMath.sin(Math.PI / 4.0), segment.distance(new Vector2D(0, -1)), 1.0e-10);
// distance to end point
Assert.assertEquals(FastMath.sqrt(8), segment.distance(new Vector2D(0, 4)), 1.0e-10);
// distance to start point
Assert.assertEquals(FastMath.sqrt(8), segment.distance(new Vector2D(0, -4)), 1.0e-10);
}
}