Package org.locationtech.jts.geom

Class LineSegment

  • All Implemented Interfaces:
    Serializable, Comparable
    public class LineSegment
extends 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
    See Also:
    Serialized Form

    • Constructor Detail

      • LineSegment

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

      • LineSegment

        public LineSegment()

    • Method Detail

      • getCoordinate

        public Coordinate getCoordinate​(int i)

      • setCoordinates

        public void setCoordinates​(LineSegment ls)

      • minX

        public double minX()
        Gets the minimum X ordinate.
        Returns:
        the minimum X ordinate

      • maxX

        public double maxX()
        Gets the maximum X ordinate.
        Returns:
        the maximum X ordinate

      • minY

        public double minY()
        Gets the minimum Y ordinate.
        Returns:
        the minimum Y ordinate

      • maxY

        public double maxY()
        Gets the maximum Y ordinate.
        Returns:
        the maximum Y ordinate

      • 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 Orientation#computeOrientation.
        Parameters:
        p - the coordinate to compare
        Returns:
        1 (LEFT) if p is to the left of this segment
        See Also:
        Orientation#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:
        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 will lie in the range (-inf, +inf), or be NaN if the line segment has zero length..

        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(org.locationtech.jts.geom.Coordinate) clamped to the range [0.0, 1.0]. If the segment has zero length, 1.0 is returned.

        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 geometry factory to use
        Returns:
        a LineString with the same geometry as this segment

      • equals

        public boolean equals​(Object o)
        Returns true if other has the same values for its points.
        Overrides:
        equals in class 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 Object
        Returns:
        a hashcode for this object

      • 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.
        Specified by:
        compareTo in interface 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.