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## com.vividsolutions.jts.algorithm
Class CGAlgorithms

    java.lang.Object
      com.vividsolutions.jts.algorithm.CGAlgorithms

Direct Known Subclasses:
  NonRobustCGAlgorithms, RobustCGAlgorithms

    public class CGAlgorithms

extends java.lang.Object

Specifies and implements various fundamental Computational Geometric algorithms. The algorithms supplied in this class are robust for double-precision floating point.

Version:
  1.7

Field Summary
`static int` | `CLOCKWISE` A value that indicates an orientation of clockwise, or a right turn.
`static int` | `COLLINEAR` A value that indicates an orientation of collinear, or no turn (straight).
`static int` | `COUNTERCLOCKWISE` A value that indicates an orientation of counterclockwise, or a left turn.
`static int` | `LEFT`
`static int` | `RIGHT`
`static int` | `STRAIGHT`

Constructor Summary
`CGAlgorithms()`

Method Summary
`static int` | `computeOrientation(Coordinate p1, Coordinate p2, Coordinate q)` Computes the orientation of a point q to the directed line segment p1-p2.
`static double` | `distanceLineLine(Coordinate A, Coordinate B, Coordinate C, Coordinate D)` Computes the distance from a line segment AB to a line segment CD Note: NON-ROBUST!
`static double` | `distancePointLine(Coordinate p, Coordinate[] line)` Computes the distance from a point to a sequence of line segments.
`static double` | `distancePointLine(Coordinate p, Coordinate A, Coordinate B)` Computes the distance from a point p to a line segment AB Note: NON-ROBUST!
`static double` | `distancePointLinePerpendicular(Coordinate p, Coordinate A, Coordinate B)` Computes the perpendicular distance from a point p to the (infinite) line containing the points AB
`static boolean` | `isCCW(Coordinate[] ring)` Computes whether a ring defined by an array of `Coordinate`s is oriented counter-clockwise.
`static boolean` | `isOnLine(Coordinate p, Coordinate[] pt)` Tests whether a point lies on the line segments defined by a list of coordinates.
`static boolean` | `isPointInRing(Coordinate p, Coordinate[] ring)` Tests whether a point lies inside or on a ring.
`static double` | `length(CoordinateSequence pts)` Computes the length of a linestring specified by a sequence of points.
`static int` | `locatePointInRing(Coordinate p, Coordinate[] ring)` Determines whether a point lies in the interior, on the boundary, or in the exterior of a ring.
`static int` | `orientationIndex(Coordinate p1, Coordinate p2, Coordinate q)` Returns the index of the direction of the point `q` relative to a vector specified by `p1-p2`.
`static double` | `signedArea(Coordinate[] ring)` Computes the signed area for a ring.
`static double` | `signedArea(CoordinateSequence ring)` Computes the signed area for a ring.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### CLOCKWISE

    public static final int CLOCKWISE

  A value that indicates an orientation of clockwise, or a right turn.

  See Also:
    Constant Field Values

### RIGHT

    public static final int RIGHT

See Also:
  Constant Field Values

### COUNTERCLOCKWISE

    public static final int COUNTERCLOCKWISE

  A value that indicates an orientation of counterclockwise, or a left turn.

  See Also:
    Constant Field Values

### LEFT

    public static final int LEFT

See Also:
  Constant Field Values

### COLLINEAR

    public static final int COLLINEAR

  A value that indicates an orientation of collinear, or no turn (straight).

  See Also:
    Constant Field Values

### STRAIGHT

    public static final int STRAIGHT

See Also:
  Constant Field Values

Constructor Detail

### CGAlgorithms

    public CGAlgorithms()

Method Detail

### orientationIndex

    public static int orientationIndex(Coordinate p1,
                                       Coordinate p2,
                                       Coordinate q)

  Returns the index of the direction of the point `q` relative to a vector specified by `p1-p2`.

  Parameters:
    `p1` - the origin point of the vector
    `p2` - the final point of the vector
    `q` - the point to compute the direction to
  Returns:
    1 if q is counter-clockwise (left) from p1-p2

### isPointInRing

    public static boolean isPointInRing(Coordinate p,
                                        Coordinate[] ring)

  Tests whether a point lies inside or on a ring. The ring may be oriented in either direction. A point lying exactly on the ring boundary is considered to be inside the ring.

  This method does not first check the point against the envelope of the ring.

  Parameters:
    `p` - point to check for ring inclusion
    `ring` - an array of coordinates representing the ring (which must have first point identical to last point)
  Returns:
    true if p is inside ring
  See Also:
    `locatePointInRing`

### locatePointInRing

    public static int locatePointInRing(Coordinate p,
                                        Coordinate[] ring)

  Determines whether a point lies in the interior, on the boundary, or in the exterior of a ring. The ring may be oriented in either direction.

  This method does not first check the point against the envelope of the ring.

  Parameters:
    `p` - point to check for ring inclusion
    `ring` - an array of coordinates representing the ring (which must have first point identical to last point)
  Returns:
    the `Location` of p relative to the ring

### isOnLine

    public static boolean isOnLine(Coordinate p,
                                   Coordinate[] pt)

  Tests whether a point lies on the line segments defined by a list of coordinates.

  Returns:
    true if the point is a vertex of the line or lies in the interior of a line segment in the linestring

### isCCW

    public static boolean isCCW(Coordinate[] ring)

  Computes whether a ring defined by an array of `Coordinate`s is oriented counter-clockwise.
  - The list of points is assumed to have the first and last points equal.
  - This will handle coordinate lists which contain repeated points.
  This algorithm is only guaranteed to work with valid rings. If the ring is invalid (e.g. self-crosses or touches), the computed result may not be correct.

  Parameters:
    `ring` - an array of Coordinates forming a ring
  Returns:
    true if the ring is oriented counter-clockwise.
  Throws:
    `java.lang.IllegalArgumentException` - if there are too few points to determine orientation (< 3)

### computeOrientation

    public static int computeOrientation(Coordinate p1,
                                         Coordinate p2,
                                         Coordinate q)

  Computes the orientation of a point q to the directed line segment p1-p2. The orientation of a point relative to a directed line segment indicates which way you turn to get to q after travelling from p1 to p2.

  Returns:
    1 if q is counter-clockwise from p1-p2

### distancePointLine

    public static double distancePointLine(Coordinate p,
                                           Coordinate A,
                                           Coordinate B)

  Computes the distance from a point p to a line segment AB Note: NON-ROBUST!

  Parameters:
    `p` - the point to compute the distance for
    `A` - one point of the line
    `B` - another point of the line (must be different to A)
  Returns:
    the distance from p to line segment AB

### distancePointLinePerpendicular

    public static double distancePointLinePerpendicular(Coordinate p,
                                                        Coordinate A,
                                                        Coordinate B)

  Computes the perpendicular distance from a point p to the (infinite) line containing the points AB

  Parameters:
    `p` - the point to compute the distance for
    `A` - one point of the line
    `B` - another point of the line (must be different to A)
  Returns:
    the distance from p to line AB

### distancePointLine

    public static double distancePointLine(Coordinate p,
                                           Coordinate[] line)

  Computes the distance from a point to a sequence of line segments.

  Parameters:
    `p` - a point
    `line` - a sequence of contiguous line segments defined by their vertices
  Returns:
    the minimum distance between the point and the line segments

### distanceLineLine

    public static double distanceLineLine(Coordinate A,
                                          Coordinate B,
                                          Coordinate C,
                                          Coordinate D)

  Computes the distance from a line segment AB to a line segment CD Note: NON-ROBUST!

  Parameters:
    `A` - a point of one line
    `B` - the second point of (must be different to A)
    `C` - one point of the line
    `D` - another point of the line (must be different to A)

### signedArea

    public static double signedArea(Coordinate[] ring)

  Computes the signed area for a ring. The signed area is positive if the ring is oriented CW, negative if the ring is oriented CCW, and zero if the ring is degenerate or flat.

  Parameters:
    `ring` - the coordinates forming the ring
  Returns:
    the signed area of the ring

### signedArea

    public static double signedArea(CoordinateSequence ring)

  Computes the signed area for a ring. The signed area is:
  - positive if the ring is oriented CW
  - negative if the ring is oriented CCW
  - zero if the ring is degenerate or flat

  Parameters:
    `ring` - the coordinates forming the ring
  Returns:
    the signed area of the ring

### length

    public static double length(CoordinateSequence pts)

  Computes the length of a linestring specified by a sequence of points.

  Parameters:
    `pts` - the points specifying the linestring
  Returns:
    the length of the linestring

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