com.vividsolutions.jts.geom

Class LineSegment

Implemented Interfaces:
Comparable, Serializable
Known Direct Subclasses:
TaggedLineSegment

public class LineSegment
extends java.lang.Object
implements Comparable, Serializable

Represents a line segment defined by two Coordinates. Provides methods to compute various geometric properties and relationships of line segments.

This class is designed to be easily mutable (to the extent of having its contained points public). This supports a common pattern of reusing a single LineSegment object as a way of computing segment properties on the segments defined by arrays or lists of Coordinates.

Version:
1.7

Field Summary

Coordinate
p0
Coordinate
p1

Constructor Summary

LineSegment()
LineSegment(Coordinate p0, Coordinate p1)
LineSegment(LineSegment ls)

Method Summary

double
angle()
Computes the angle that the vector defined by this segment makes with the X-axis.
Coordinate
closestPoint(Coordinate p)
Computes the closest point on this line segment to another point.
Coordinate[]
closestPoints(LineSegment line)
Computes the closest points on two line segments.
int
compareTo(Object o)
Compares this object with the specified object for order.
double
distance(Coordinate p)
Computes the distance between this line segment and a given point.
double
distance(LineSegment ls)
Computes the distance between this line segment and another segment.
double
distancePerpendicular(Coordinate p)
Computes the perpendicular distance between the (infinite) line defined by this line segment and a point.
boolean
equals(Object o)
Returns true if other has the same values for its points.
boolean
equalsTopo(LineSegment other)
Returns true if other is topologically equal to this LineSegment (e.g.
Coordinate
getCoordinate(int i)
double
getLength()
Computes the length of the line segment.
Coordinate
intersection(LineSegment line)
Computes an intersection point between two segments, if there is one.
boolean
isHorizontal()
Tests whether the segment is horizontal.
boolean
isVertical()
Tests whether the segment is vertical.
void
normalize()
Puts the line segment into a normalized form.
int
orientationIndex(LineSegment seg)
Determines the orientation of a LineSegment relative to this segment.
Coordinate
pointAlong(double segmentLengthFraction)
Computes the Coordinate that lies a given fraction along the line defined by this segment.
Coordinate
project(Coordinate p)
Compute the projection of a point onto the line determined by this line segment.
LineSegment
project(LineSegment seg)
Project a line segment onto this line segment and return the resulting line segment.
double
projectionFactor(Coordinate p)
Computes the Projection Factor for the projection of the point p onto this LineSegment.
void
reverse()
Reverses the direction of the line segment.
void
setCoordinates(Coordinate p0, Coordinate p1)
void
setCoordinates(LineSegment ls)
String
toString()

Field Details

p0

public Coordinate p0

p1

public Coordinate p1

Constructor Details

LineSegment

public LineSegment()

LineSegment

public LineSegment(Coordinate p0,
                   Coordinate p1)

LineSegment

public LineSegment(LineSegment ls)

Method Details

angle

public double angle()
Computes the angle that the vector defined by this segment makes with the X-axis. The angle will be in the range [ -PI, PI ] radians.
Returns:
the angle this segment makes with the X-axis (in radians)

closestPoint

public Coordinate closestPoint(Coordinate p)
Computes the closest point on this line segment to another point.
Parameters:
p - the point to find the closest point to
Returns:
a Coordinate which is the closest point on the line segment to the point p

closestPoints

public Coordinate[] closestPoints(LineSegment line)
Computes the closest points on two line segments.
Parameters:
Returns:
a pair of Coordinates which are the closest points on the line segments

compareTo

public int compareTo(Object o)
Compares this object with the specified object for order. Uses the standard lexicographic ordering for the points in the LineSegment.
Parameters:
o - the LineSegment with which this LineSegment is being compared
Returns:
a negative integer, zero, or a positive integer as this LineSegment is less than, equal to, or greater than the specified LineSegment

distance

public double distance(Coordinate p)
Computes the distance between this line segment and a given point.
Returns:
the distance from this segment to the given point

distance

public double distance(LineSegment ls)
Computes the distance between this line segment and another segment.
Returns:
the distance to the other segment

distancePerpendicular

public double distancePerpendicular(Coordinate p)
Computes the perpendicular distance between the (infinite) line defined by this line segment and a point.
Returns:
the perpendicular distance between the defined line and the given point

equals

public boolean equals(Object o)
Returns true if other has the same values for its points.
Parameters:
Returns:
true if other is a LineSegment with the same values for the x and y ordinates.

equalsTopo

public boolean equalsTopo(LineSegment other)
Returns true if other is topologically equal to this LineSegment (e.g. irrespective of orientation).
Parameters:
other - a LineSegment with which to do the comparison.
Returns:
true if other is a LineSegment with the same values for the x and y ordinates.

getCoordinate

public Coordinate getCoordinate(int i)

getLength

public double getLength()
Computes the length of the line segment.
Returns:
the length of the line segment

intersection

public Coordinate intersection(LineSegment line)
Computes an intersection point between two segments, if there is one. There may be 0, 1 or many intersection points between two segments. If there are 0, null is returned. If there is 1 or more, a single one is returned (chosen at the discretion of the algorithm). If more information is required about the details of the intersection, the RobustLineIntersector class should be used.
Parameters:
line -
Returns:
an intersection point, or null if there is none

isHorizontal

public boolean isHorizontal()
Tests whether the segment is horizontal.
Returns:
true if the segment is horizontal

isVertical

public boolean isVertical()
Tests whether the segment is vertical.
Returns:
true if the segment is vertical

normalize

public void normalize()

orientationIndex

public int orientationIndex(LineSegment seg)
Determines the orientation of a LineSegment relative to this segment. The concept of orientation is specified as follows: Given two line segments A and L,
  • A is to the left of a segment L if A lies wholly in the closed half-plane lying to the left of L
  • A is to the right of a segment L if A lies wholly in the closed half-plane lying to the right of L
  • otherwise, A has indeterminate orientation relative to L. This happens if A is collinear with L or if A crosses the line determined by L.
Parameters:
seg - the LineSegment to compare
Returns:
1 if seg is to the left of this segment

pointAlong

public Coordinate pointAlong(double segmentLengthFraction)
Computes the Coordinate that lies a given fraction along the line defined by this segment. A fraction of 0.0 returns the start point of the segment; a fraction of 1.0 returns the end point of the segment.
Parameters:
segmentLengthFraction - the fraction of the segment length along the line
Returns:
the point at that distance

project

public Coordinate project(Coordinate p)
Compute the projection of a point onto the line determined by this line segment.

Note that the projected point may lie outside the line segment. If this is the case, the projection factor will lie outside the range [0.0, 1.0].


project

public LineSegment project(LineSegment seg)
Project a line segment onto this line segment and return the resulting line segment. The returned line segment will be a subset of the target line line segment. This subset may be null, if the segments are oriented in such a way that there is no projection.

Note that the returned line may have zero length (i.e. the same endpoints). This can happen for instance if the lines are perpendicular to one another.

Parameters:
seg - the line segment to project
Returns:
the projected line segment, or null if there is no overlap

projectionFactor

public double projectionFactor(Coordinate p)
Computes the Projection Factor for the projection of the point p onto this LineSegment. The Projection Factor is the constant r by which the vector for this segment must be multiplied to equal the vector for the projection of p on the line defined by this segment.

reverse

public void reverse()
Reverses the direction of the line segment.

setCoordinates

public void setCoordinates(Coordinate p0,
                           Coordinate p1)

setCoordinates

public void setCoordinates(LineSegment ls)

toString

public String toString()