com.revolsys.jts.algorithm

Class CGAlgorithms

java.lang.Object

com.revolsys.jts.algorithm.CGAlgorithms

Direct Known Subclasses:

RobustCGAlgorithms

public class CGAlgorithms
extends 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

Fields

Modifier and Type	Field and Description
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 A value that indicates an orientation of counterclockwise, or a left turn.
static int	RIGHT A value that indicates an orientation of clockwise, or a right turn.
static int	STRAIGHT A value that indicates an orientation of collinear, or no turn (straight).

Constructor Summary

Constructors

Constructor and Description
CGAlgorithms()

Method Summary

Methods

Modifier and Type	Method and Description
static double	distancePointLinePerpendicular(Point p, Point A, Point B) Computes the perpendicular distance from a point p to the (infinite) line containing the points AB
static boolean	isCCW(Point[] ring) Computes whether a ring defined by an array of Coordinatess is oriented counter-clockwise.
static boolean	isOnLine(Point p, LineString line) Tests whether a point lies on the line segments defined by a list of coordinates.
static boolean	isPointInRing(Point point, LineString 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

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

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

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

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

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

See Also:

Constant Field Values

Constructor Detail

CGAlgorithms

public CGAlgorithms()

Method Detail

distancePointLinePerpendicular

public static double distancePointLinePerpendicular(Point p,
                                    Point A,
                                    Point 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

isCCW

public static boolean isCCW(Point[] ring)

Computes whether a ring defined by an array of Coordinatess 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 Point forming a ring

Returns:

true if the ring is oriented counter-clockwise.

Throws:

IllegalArgumentException - if there are too few points to determine orientation (< 4)

isOnLine

public static boolean isOnLine(Point p,
               LineString line)

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

isPointInRing

public static boolean isPointInRing(Point point,
                    LineString ring)