Package org.locationtech.jts.algorithm

Class MinimumDiameter

java.lang.Object

org.locationtech.jts.algorithm.MinimumDiameter

public class MinimumDiameter
extends java.lang.Object

Computes the minimum diameter of a Geometry. The minimum diameter is defined to be the width of the smallest band that contains the geometry, where a band is a strip of the plane defined by two parallel lines. This can be thought of as the smallest hole that the geometry can be moved through, with a single rotation.

The first step in the algorithm is computing the convex hull of the Geometry. If the input Geometry is known to be convex, a hint can be supplied to avoid this computation.

This class can also be used to compute a line segment representing the minimum diameter, the supporting line segment of the minimum diameter, and a minimum rectangle enclosing the input geometry. This rectangle will have width equal to the minimum diameter, and have one side parallel to the supporting segment.

Version:

1.7

See Also:

ConvexHull

Field Summary

Fields

Modifier and Type	Field	Description
private Coordinate[]	convexHullPts
private Geometry	inputGeom
private boolean	isConvex
private LineSegment	minBaseSeg
private int	minPtIndex
private double	minWidth
private Coordinate	minWidthPt

Constructor Summary

Constructors

Constructor	Description
MinimumDiameter(Geometry inputGeom)	Compute a minimum diameter for a given Geometry.
MinimumDiameter(Geometry inputGeom, boolean isConvex)	Compute a minimum diameter for a giver Geometry, with a hint if the Geometry is convex (e.g.

Method Summary

Modifier and Type	Method	Description
private static double	computeC(double a, double b, Coordinate p)
private void	computeConvexRingMinDiameter(Coordinate[] pts)	Compute the width information for a ring of Coordinates.
private void	computeMinimumDiameter()
private static LineSegment	computeSegmentForLine(double a, double b, double c)
private void	computeWidthConvex(Geometry convexGeom)
private int	findMaxPerpDistance(Coordinate[] pts, LineSegment seg, int startIndex)
LineString	getDiameter()	Gets a LineString which is a minimum diameter
double	getLength()	Gets the length of the minimum diameter of the input Geometry
static Geometry	getMinimumDiameter(Geometry geom)	Gets the length of the minimum diameter enclosing a geometry
Geometry	getMinimumRectangle()	Gets the minimum rectangular Polygon which encloses the input geometry.
static Geometry	getMinimumRectangle(Geometry geom)	Gets the minimum rectangle enclosing a geometry.
LineString	getSupportingSegment()	Gets the segment forming the base of the minimum diameter
Coordinate	getWidthCoordinate()	Gets the Coordinate forming one end of the minimum diameter
private static int	nextIndex(Coordinate[] pts, int index)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

inputGeom

private final Geometry inputGeom

isConvex

private final boolean isConvex

convexHullPts

private Coordinate[] convexHullPts

minBaseSeg

private LineSegment minBaseSeg

minWidthPt

private Coordinate minWidthPt

minPtIndex

private int minPtIndex

minWidth

private double minWidth

Constructor Detail

MinimumDiameter

public MinimumDiameter(Geometry inputGeom)

Compute a minimum diameter for a given Geometry.

Parameters:

inputGeom - a Geometry

MinimumDiameter

public MinimumDiameter(Geometry inputGeom,
                       boolean isConvex)

Compute a minimum diameter for a giver Geometry, with a hint if the Geometry is convex (e.g. a convex Polygon or LinearRing, or a two-point LineString, or a Point).

Parameters:

inputGeom - a Geometry which is convex

isConvex - true if the input geometry is convex

Method Detail

getMinimumRectangle

public static Geometry getMinimumRectangle(Geometry geom)

Gets the minimum rectangle enclosing a geometry.

Parameters:

geom - the geometry

Returns:

the minimum rectangle enclosing the geometry

getMinimumDiameter

public static Geometry getMinimumDiameter(Geometry geom)

Gets the length of the minimum diameter enclosing a geometry

Parameters:

geom - the geometry

Returns:

the length of the minimum diameter of the geometry

getLength

public double getLength()

Gets the length of the minimum diameter of the input Geometry

Returns:

the length of the minimum diameter

getWidthCoordinate

public Coordinate getWidthCoordinate()

Gets the Coordinate forming one end of the minimum diameter

Returns:

a coordinate forming one end of the minimum diameter

getSupportingSegment

public LineString getSupportingSegment()

Gets the segment forming the base of the minimum diameter

Returns:

the segment forming the base of the minimum diameter

getDiameter

public LineString getDiameter()

Gets a LineString which is a minimum diameter

Returns:

a LineString which is a minimum diameter

computeMinimumDiameter

private void computeMinimumDiameter()

computeWidthConvex

private void computeWidthConvex(Geometry convexGeom)

computeConvexRingMinDiameter

private void computeConvexRingMinDiameter(Coordinate[] pts)

Compute the width information for a ring of Coordinates. Leaves the width information in the instance variables.

Parameters:

pts -

findMaxPerpDistance

private int findMaxPerpDistance(Coordinate[] pts,
                                LineSegment seg,
                                int startIndex)

nextIndex

private static int nextIndex(Coordinate[] pts,
                             int index)

getMinimumRectangle

public Geometry getMinimumRectangle()

Gets the minimum rectangular Polygon which encloses the input geometry. The rectangle has width equal to the minimum diameter, and a longer length. If the convex hull of the input is degenerate (a line or point) a LineString or Point is returned.

The minimum rectangle can be used as an extremely generalized representation for the given geometry.

Returns:

the minimum rectangle enclosing the input (or a line or point if degenerate)

computeC

private static double computeC(double a,
                               double b,
                               Coordinate p)

computeSegmentForLine

private static LineSegment computeSegmentForLine(double a,
                                                 double b,
                                                 double c)