geos::algorithm::MinimumDiameter Class Reference

Computes the minimum diameter of a geom::Geometry. More...

#include <MinimumDiameter.h>

Collaboration diagram for geos::algorithm::MinimumDiameter:

Public Member Functions
	~MinimumDiameter ()=default
	MinimumDiameter (const geom::Geometry *newInputGeom)
	Compute a minimum diameter for a given Geometry. More...
	MinimumDiameter (const geom::Geometry *newInputGeom, const bool newIsConvex)
	Compute a minimum diameter for a given Geometry, with a hint if the Geometry is convex (e.g. a convex Polygon or LinearRing, or a two-point LineString, or a Point). More...
double	getLength ()
	Gets the length of the minimum diameter of the input Geometry. More...
const geom::Coordinate &	getWidthCoordinate ()
	Gets the geom::Coordinate forming one end of the minimum diameter. More...
std::unique_ptr< geom::LineString >	getSupportingSegment ()
	Gets the segment forming the base of the minimum diameter. More...
std::unique_ptr< geom::LineString >	getDiameter ()
	Gets a LineString which is a minimum diameter. More...
std::unique_ptr< geom::Geometry >	getMinimumRectangle ()
	Gets the minimum rectangular Polygon which encloses the input geometry. More...

Static Public Member Functions
static std::unique_ptr< geom::Geometry >	getMinimumRectangle (geom::Geometry *geom)
	Gets the minimum rectangle enclosing a geometry. More...
static std::unique_ptr< geom::Geometry >	getMinimumDiameter (geom::Geometry *geom)
	Gets the length of the minimum diameter enclosing a geometry. More...

Private Member Functions
void	computeMinimumDiameter ()
void	computeWidthConvex (const geom::Geometry *geom)
void	computeConvexRingMinDiameter (const geom::CoordinateSequence *pts)
unsigned int	findMaxPerpDistance (const geom::CoordinateSequence *pts, const geom::LineSegment *seg, unsigned int startIndex)

Static Private Member Functions
static unsigned int	getNextIndex (const geom::CoordinateSequence *pts, unsigned int index)
static double	computeC (double a, double b, const geom::Coordinate &p)
static geom::LineSegment	computeSegmentForLine (double a, double b, double c)

Private Attributes
const geom::Geometry *	inputGeom
bool	isConvex
std::unique_ptr< geom::CoordinateSequence >	convexHullPts
geom::LineSegment	minBaseSeg
geom::Coordinate	minWidthPt
size_t	minPtIndex
double	minWidth

Detailed Description

Computes the minimum diameter of a geom::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.

See also

ConvexHull

Definition at line 63 of file MinimumDiameter.h.

Constructor & Destructor Documentation

geos::algorithm::MinimumDiameter::~MinimumDiameter ( )

default

geos::algorithm::MinimumDiameter::MinimumDiameter

(

const geom::Geometry *

newInputGeom

)

Compute a minimum diameter for a given Geometry.

Parameters

newInputGeom

a Geometry

geos::algorithm::MinimumDiameter::MinimumDiameter	(	const geom::Geometry *	newInputGeom,
		const bool	newIsConvex
	)

Compute a minimum diameter for a given 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

newInputGeom	a Geometry which is convex
newIsConvex	true if the input geometry is convex

Member Function Documentation

static double geos::algorithm::MinimumDiameter::computeC ( double  a, double  b, const geom::Coordinate &  p  )

staticprivate

void geos::algorithm::MinimumDiameter::computeConvexRingMinDiameter ( const geom::CoordinateSequence *  pts )

private

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

Parameters

pts

Returns

void geos::algorithm::MinimumDiameter::computeMinimumDiameter ( )

private

static geom::LineSegment geos::algorithm::MinimumDiameter::computeSegmentForLine ( double  a, double  b, double  c  )

staticprivate

void geos::algorithm::MinimumDiameter::computeWidthConvex ( const geom::Geometry *  geom )

private

unsigned int geos::algorithm::MinimumDiameter::findMaxPerpDistance ( const geom::CoordinateSequence *  pts, const geom::LineSegment *  seg, unsigned int  startIndex  )

private

std::unique_ptr<geom::LineString> geos::algorithm::MinimumDiameter::getDiameter

(

)

Gets a LineString which is a minimum diameter.

Returns

a LineString which is a minimum diameter

double geos::algorithm::MinimumDiameter::getLength

(

)

Gets the length of the minimum diameter of the input Geometry.

Returns

the length of the minimum diameter

static std::unique_ptr<geom::Geometry> geos::algorithm::MinimumDiameter::getMinimumDiameter ( geom::Geometry *  geom )

static

Gets the length of the minimum diameter enclosing a geometry.

Parameters

geom	the geometry

Returns

the length of the minimum diameter of the geometry

std::unique_ptr<geom::Geometry> geos::algorithm::MinimumDiameter::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 hill 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)

static std::unique_ptr<geom::Geometry> geos::algorithm::MinimumDiameter::getMinimumRectangle ( geom::Geometry *  geom )

static

Gets the minimum rectangle enclosing a geometry.

Parameters

geom	the geometry

Returns

the minimum rectangle enclosing the geometry

static unsigned int geos::algorithm::MinimumDiameter::getNextIndex ( const geom::CoordinateSequence *  pts, unsigned int  index  )

staticprivate

std::unique_ptr<geom::LineString> geos::algorithm::MinimumDiameter::getSupportingSegment

(

)

Gets the segment forming the base of the minimum diameter.

Returns

the segment forming the base of the minimum diameter

const geom::Coordinate& geos::algorithm::MinimumDiameter::getWidthCoordinate

(

)

Gets the geom::Coordinate forming one end of the minimum diameter.

Returns

a coordinate forming one end of the minimum diameter

Member Data Documentation

std::unique_ptr<geom::CoordinateSequence> geos::algorithm::MinimumDiameter::convexHullPts

private

Definition at line 68 of file MinimumDiameter.h.

const geom::Geometry* geos::algorithm::MinimumDiameter::inputGeom

private

Definition at line 65 of file MinimumDiameter.h.

bool geos::algorithm::MinimumDiameter::isConvex

private

Definition at line 66 of file MinimumDiameter.h.

geom::LineSegment geos::algorithm::MinimumDiameter::minBaseSeg

private

Definition at line 70 of file MinimumDiameter.h.

size_t geos::algorithm::MinimumDiameter::minPtIndex

private

Definition at line 72 of file MinimumDiameter.h.

double geos::algorithm::MinimumDiameter::minWidth

private

Definition at line 73 of file MinimumDiameter.h.

geom::Coordinate geos::algorithm::MinimumDiameter::minWidthPt

private

Definition at line 71 of file MinimumDiameter.h.

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The documentation for this class was generated from the following file:

• MinimumDiameter.h