com.vividsolutions.jts.geom
Class LineSegment

java.lang.Object
  com.vividsolutions.jts.geom.LineSegment

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable

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

See Also:

Serialized Form

Field Summary

Coordinate	p0
Coordinate	p1

Constructor Summary

LineSegment()

LineSegment(Coordinate p0, Coordinate p1)

LineSegment(double x0, double y0, double x1, double y1)

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(java.lang.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(java.lang.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.
int	hashCode() Gets a hashcode for this object.
Coordinate	intersection(LineSegment line) Computes an intersection point between two line segments, if there is one.
boolean	isHorizontal() Tests whether the segment is horizontal.
boolean	isVertical() Tests whether the segment is vertical.
Coordinate	lineIntersection(LineSegment line) Computes the intersection point of the lines of infinite extent defined by two line segments (if there is one).
Coordinate	midPoint() Computes the midpoint of the segment
static Coordinate	midPoint(Coordinate p0, Coordinate p1) Computes the midpoint of a segment
void	normalize() Puts the line segment into a normalized form.
int	orientationIndex(Coordinate p) Determines the orientation index of a Coordinate relative to this segment.
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	pointAlongOffset(double segmentLengthFraction, double offsetDistance) Computes the Coordinate that lies a given fraction along the line defined by this segment and offset from the segment by a given distance.
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.
double	segmentFraction(Coordinate inputPt) Computes the fraction of distance (in [0.0, 1.0]) that the projection of a point occurs along this line segment.
void	setCoordinates(Coordinate p0, Coordinate p1)
void	setCoordinates(LineSegment ls)
LineString	toGeometry(GeometryFactory geomFactory) Creates a LineString with the same coordinates as this segment
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

p0

public Coordinate p0

p1

public Coordinate p1

Constructor Detail

LineSegment

public LineSegment(Coordinate p0,
                   Coordinate p1)

LineSegment

public LineSegment(double x0,
                   double y0,
                   double x1,
                   double y1)

LineSegment

public LineSegment(LineSegment ls)

LineSegment

public LineSegment()

Method Detail

getCoordinate

public Coordinate getCoordinate(int i)

setCoordinates

public void setCoordinates(LineSegment ls)

setCoordinates

public void setCoordinates(Coordinate p0,
                           Coordinate p1)

getLength

public double getLength()

Computes the length of the line segment.

Returns:

the length of the line segment

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

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

orientationIndex

public int orientationIndex(Coordinate p)

Determines the orientation index of a Coordinate relative to this segment. The orientation index is as defined in CGAlgorithms.computeOrientation(com.vividsolutions.jts.geom.Coordinate, com.vividsolutions.jts.geom.Coordinate, com.vividsolutions.jts.geom.Coordinate).

Parameters:

p - the coordinate to compare

Returns:

1 (LEFT) if p is to the left of this segment

See Also:

CGAlgorithms.computeOrientation(Coordinate, Coordinate, Coordinate)

reverse

public void reverse()

Reverses the direction of the line segment.

normalize

public void normalize()

Puts the line segment into a normalized form. This is useful for using line segments in maps and indexes when topological equality rather than exact equality is desired. A segment in normalized form has the first point smaller than the second (according to the standard ordering on Coordinate).

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)

midPoint

public Coordinate midPoint()

Computes the midpoint of the segment

Returns:

the midpoint of the segment

midPoint

public static Coordinate midPoint(Coordinate p0,
                                  Coordinate p1)

Computes the midpoint of a segment

Returns:

the midpoint of the segment

distance

public double distance(LineSegment ls)

Computes the distance between this line segment and another segment.

Returns:

the distance to the other segment

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

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

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. If the fraction is < 0.0 or > 1.0 the point returned will lie before the start or beyond the end of the segment.

Parameters:

segmentLengthFraction - the fraction of the segment length along the line

Returns:

the point at that distance

pointAlongOffset

public Coordinate pointAlongOffset(double segmentLengthFraction,
                                   double offsetDistance)

Computes the Coordinate that lies a given fraction along the line defined by this segment and offset from the segment by a given distance. A fraction of 0.0 offsets from the start point of the segment; a fraction of 1.0 offsets from the end point of the segment. The computed point is offset to the left of the line if the offset distance is positive, to the right if negative.

Parameters:

segmentLengthFraction - the fraction of the segment length along the line

offsetDistance - the distance the point is offset from the segment (positive is to the left, negative is to the right)

Returns:

the point at that distance and offset

Throws:

java.lang.IllegalStateException - if the segment has zero length

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.

The projection factor returned will be in the range (-inf, +inf).

Parameters:

p - the point to compute the factor for

Returns:

the projection factor for the point

segmentFraction

public double segmentFraction(Coordinate inputPt)

Computes the fraction of distance (in [0.0, 1.0]) that the projection of a point occurs along this line segment. If the point is beyond either ends of the line segment, the closest fractional value (0.0 or 1.0) is returned.

Essentially, this is the projectionFactor(com.vividsolutions.jts.geom.Coordinate) clamped to the range [0.0, 1.0].

Parameters:

inputPt - the point

Returns:

the fraction along the line segment the projection of the point occurs

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

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:

line - the segment to find the closest point to

Returns:

a pair of Coordinates which are the closest points on the line segments

intersection

public Coordinate intersection(LineSegment line)

Computes an intersection point between two line 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, exactly one of them 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 - a line segment

Returns:

an intersection point, or null if there is none

See Also:

RobustLineIntersector

lineIntersection

public Coordinate lineIntersection(LineSegment line)

Computes the intersection point of the lines of infinite extent defined by two line segments (if there is one). There may be 0, 1 or an infinite number of intersection points between two lines. If there is a unique intersection point, it is returned. Otherwise, null is returned. If more information is required about the details of the intersection, the RobustLineIntersector class should be used.

Parameters:

line - a line segment defining an straight line with infinite extent

Returns:

an intersection point, or null if there is no point of intersection or an infinite number of intersection points

See Also:

RobustLineIntersector

toGeometry

public LineString toGeometry(GeometryFactory geomFactory)

Creates a LineString with the same coordinates as this segment

Parameters:

geomFactory - the geometery factory to use

Returns:

a LineString with the same geometry as this segment

equals

public boolean equals(java.lang.Object o)

Returns true if other has the same values for its points.

Overrides:

equals in class java.lang.Object

Parameters:

o - 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.

hashCode

public int hashCode()

Gets a hashcode for this object.

Overrides:

hashCode in class java.lang.Object

Returns:

a hashcode for this object

compareTo

public int compareTo(java.lang.Object o)

Compares this object with the specified object for order. Uses the standard lexicographic ordering for the points in the LineSegment.

Specified by:

compareTo in interface java.lang.Comparable

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

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.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object