Class LineIntersector
- java.lang.Object
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- org.locationtech.jts.algorithm.LineIntersector
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- Direct Known Subclasses:
RobustLineIntersector
public abstract class LineIntersector extends java.lang.Object
ALineIntersector
is an algorithm that can both test whether two line segments intersect and compute the intersection point(s) if they do.There are three possible outcomes when determining whether two line segments intersect:
NO_INTERSECTION
- the segments do not intersectPOINT_INTERSECTION
- the segments intersect in a single pointCOLLINEAR_INTERSECTION
- the segments are collinear and they intersect in a line segment
isProper()
test for this situation.The intersection point(s) may be computed in a precise or non-precise manner. Computing an intersection point precisely involves rounding it via a supplied
PrecisionModel
.LineIntersectors do not perform an initial envelope intersection test to determine if the segments are disjoint. This is because this class is likely to be used in a context where envelope overlap is already known to occur (or be likely).
- Version:
- 1.7
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Field Summary
Fields Modifier and Type Field Description static int
COLLINEAR
static int
COLLINEAR_INTERSECTION
Indicates that line segments intersect in a line segmentstatic int
DO_INTERSECT
static int
DONT_INTERSECT
These are deprecated, due to ambiguous namingstatic int
NO_INTERSECTION
Indicates that line segments do not intersectstatic int
POINT_INTERSECTION
Indicates that line segments intersect in a single point
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Constructor Summary
Constructors Constructor Description LineIntersector()
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods Modifier and Type Method Description static double
computeEdgeDistance(Coordinate p, Coordinate p0, Coordinate p1)
Computes the "edge distance" of an intersection point p along a segment.abstract void
computeIntersection(Coordinate p, Coordinate p1, Coordinate p2)
Compute the intersection of a point p and the line p1-p2.void
computeIntersection(Coordinate p1, Coordinate p2, Coordinate p3, Coordinate p4)
Computes the intersection of the lines p1-p2 and p3-p4.double
getEdgeDistance(int segmentIndex, int intIndex)
Computes the "edge distance" of an intersection point along the specified input line segment.Coordinate
getEndpoint(int segmentIndex, int ptIndex)
Gets an endpoint of an input segment.int
getIndexAlongSegment(int segmentIndex, int intIndex)
Computes the index (order) of the intIndex'th intersection point in the direction of a specified input line segmentCoordinate
getIntersection(int intIndex)
Returns the intIndex'th intersection pointCoordinate
getIntersectionAlongSegment(int segmentIndex, int intIndex)
Computes the intIndex'th intersection point in the direction of a specified input line segmentint
getIntersectionNum()
Returns the number of intersection points found.boolean
hasIntersection()
Tests whether the input geometries intersect.boolean
isInteriorIntersection()
Tests whether either intersection point is an interior point of one of the input segments.boolean
isInteriorIntersection(int inputLineIndex)
Tests whether either intersection point is an interior point of the specified input segment.boolean
isIntersection(Coordinate pt)
Test whether a point is a intersection point of two line segments.boolean
isProper()
Tests whether an intersection is proper.static double
nonRobustComputeEdgeDistance(Coordinate p, Coordinate p1, Coordinate p2)
This function is non-robust, since it may compute the square of large numbers.void
setMakePrecise(PrecisionModel precisionModel)
Deprecated.usesetPrecisionModel
insteadvoid
setPrecisionModel(PrecisionModel precisionModel)
Force computed intersection to be rounded to a given precision model.java.lang.String
toString()
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Field Detail
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DONT_INTERSECT
public static final int DONT_INTERSECT
These are deprecated, due to ambiguous naming- See Also:
- Constant Field Values
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DO_INTERSECT
public static final int DO_INTERSECT
- See Also:
- Constant Field Values
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COLLINEAR
public static final int COLLINEAR
- See Also:
- Constant Field Values
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NO_INTERSECTION
public static final int NO_INTERSECTION
Indicates that line segments do not intersect- See Also:
- Constant Field Values
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POINT_INTERSECTION
public static final int POINT_INTERSECTION
Indicates that line segments intersect in a single point- See Also:
- Constant Field Values
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COLLINEAR_INTERSECTION
public static final int COLLINEAR_INTERSECTION
Indicates that line segments intersect in a line segment- See Also:
- Constant Field Values
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Method Detail
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computeEdgeDistance
public static double computeEdgeDistance(Coordinate p, Coordinate p0, Coordinate p1)
Computes the "edge distance" of an intersection point p along a segment. The edge distance is a metric of the point along the edge. The metric used is a robust and easy to compute metric function. It is not equivalent to the usual Euclidean metric. It relies on the fact that either the x or the y ordinates of the points in the edge are unique, depending on whether the edge is longer in the horizontal or vertical direction.NOTE: This function may produce incorrect distances for inputs where p is not precisely on p1-p2 (E.g. p = (139,9) p1 = (139,10), p2 = (280,1) produces distance 0.0, which is incorrect.
My hypothesis is that the function is safe to use for points which are the result of rounding points which lie on the line, but not safe to use for truncated points.
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nonRobustComputeEdgeDistance
public static double nonRobustComputeEdgeDistance(Coordinate p, Coordinate p1, Coordinate p2)
This function is non-robust, since it may compute the square of large numbers. Currently not sure how to improve this.
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setMakePrecise
public void setMakePrecise(PrecisionModel precisionModel)
Deprecated.usesetPrecisionModel
insteadForce computed intersection to be rounded to a given precision model- Parameters:
precisionModel
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setPrecisionModel
public void setPrecisionModel(PrecisionModel precisionModel)
Force computed intersection to be rounded to a given precision model. No getter is provided, because the precision model is not required to be specified.- Parameters:
precisionModel
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getEndpoint
public Coordinate getEndpoint(int segmentIndex, int ptIndex)
Gets an endpoint of an input segment.- Parameters:
segmentIndex
- the index of the input segment (0 or 1)ptIndex
- the index of the endpoint (0 or 1)- Returns:
- the specified endpoint
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computeIntersection
public abstract void computeIntersection(Coordinate p, Coordinate p1, Coordinate p2)
Compute the intersection of a point p and the line p1-p2. This function computes the boolean value of the hasIntersection test. The actual value of the intersection (if there is one) is equal to the value ofp
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computeIntersection
public void computeIntersection(Coordinate p1, Coordinate p2, Coordinate p3, Coordinate p4)
Computes the intersection of the lines p1-p2 and p3-p4. This function computes both the boolean value of the hasIntersection test and the (approximate) value of the intersection point itself (if there is one).
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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hasIntersection
public boolean hasIntersection()
Tests whether the input geometries intersect.- Returns:
- true if the input geometries intersect
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getIntersectionNum
public int getIntersectionNum()
Returns the number of intersection points found. This will be either 0, 1 or 2.- Returns:
- the number of intersection points found (0, 1, or 2)
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getIntersection
public Coordinate getIntersection(int intIndex)
Returns the intIndex'th intersection point- Parameters:
intIndex
- is 0 or 1- Returns:
- the intIndex'th intersection point
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isIntersection
public boolean isIntersection(Coordinate pt)
Test whether a point is a intersection point of two line segments. Note that if the intersection is a line segment, this method only tests for equality with the endpoints of the intersection segment. It does not return true if the input point is internal to the intersection segment.- Returns:
- true if the input point is one of the intersection points.
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isInteriorIntersection
public boolean isInteriorIntersection()
Tests whether either intersection point is an interior point of one of the input segments.- Returns:
true
if either intersection point is in the interior of one of the input segments
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isInteriorIntersection
public boolean isInteriorIntersection(int inputLineIndex)
Tests whether either intersection point is an interior point of the specified input segment.- Returns:
true
if either intersection point is in the interior of the input segment
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isProper
public boolean isProper()
Tests whether an intersection is proper.
The intersection between two line segments is considered proper if they intersect in a single point in the interior of both segments (e.g. the intersection is a single point and is not equal to any of the endpoints).The intersection between a point and a line segment is considered proper if the point lies in the interior of the segment (e.g. is not equal to either of the endpoints).
- Returns:
- true if the intersection is proper
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getIntersectionAlongSegment
public Coordinate getIntersectionAlongSegment(int segmentIndex, int intIndex)
Computes the intIndex'th intersection point in the direction of a specified input line segment- Parameters:
segmentIndex
- is 0 or 1intIndex
- is 0 or 1- Returns:
- the intIndex'th intersection point in the direction of the specified input line segment
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getIndexAlongSegment
public int getIndexAlongSegment(int segmentIndex, int intIndex)
Computes the index (order) of the intIndex'th intersection point in the direction of a specified input line segment- Parameters:
segmentIndex
- is 0 or 1intIndex
- is 0 or 1- Returns:
- the index of the intersection point along the input segment (0 or 1)
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getEdgeDistance
public double getEdgeDistance(int segmentIndex, int intIndex)
Computes the "edge distance" of an intersection point along the specified input line segment.- Parameters:
segmentIndex
- is 0 or 1intIndex
- is 0 or 1- Returns:
- the edge distance of the intersection point
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