Circle geometry type. More...

#include <qgscircle.h>

Inheritance diagram for QgsCircle:

Public Member Functions
	QgsCircle ()

	QgsCircle (const QgsPoint &center, double radius, double azimuth=0)
	Constructs a circle by defining all the members.

double	area () const override
	The area of the ellipse.

QDomElement	asGml2 (QDomDocument &doc, int precision=17, const QString &ns="gml", QgsAbstractGeometry::AxisOrder axisOrder=QgsAbstractGeometry::AxisOrder::XY) const
	Returns a GML2 representation of the geometry.

QDomElement	asGml3 (QDomDocument &doc, int precision=17, const QString &ns="gml", QgsAbstractGeometry::AxisOrder axisOrder=QgsAbstractGeometry::AxisOrder::XY) const
	Returns a GML3 representation of the geometry.

QgsRectangle	boundingBox () const override
	Returns the minimal bounding box for the ellipse.

bool	contains (const QgsPoint &point, double epsilon=1E-8) const
	Returns `true` if the circle contains the point.

int	innerTangents (const QgsCircle &other, QgsPointXY &line1P1, QgsPointXY &line1P2, QgsPointXY &line2P1, QgsPointXY &line2P2) const
	Calculates the inner tangent points between this circle and an other circle.

int	intersections (const QgsCircle &other, QgsPoint &intersection1, QgsPoint &intersection2, bool useZ=false) const
	Calculates the intersections points between this circle and an other circle.

QVector< QgsPoint >	northQuadrant () const
	The four quadrants of the ellipse.

int	outerTangents (const QgsCircle &other, QgsPointXY &line1P1, QgsPointXY &line1P2, QgsPointXY &line2P1, QgsPointXY &line2P2) const
	Calculates the outer tangent points between this circle and an other circle.

double	perimeter () const override
	The circumference of the ellipse using first approximation of Ramanujan.

double	radius () const
	Returns the radius of the circle.

void	setRadius (double radius)
	Sets the radius of the circle.

void	setSemiMajorAxis (double semiMajorAxis) override
	Inherited method.

void	setSemiMinorAxis (double semiMinorAxis) override
	Inherited method.

bool	tangentToPoint (const QgsPointXY &p, QgsPointXY &pt1, QgsPointXY &pt2) const
	Calculates the tangent points between this circle and the point p.

QgsCircularString *	toCircularString (bool oriented=false) const
	Returns a circular string from the circle.

QString	toString (int pointPrecision=17, int radiusPrecision=17, int azimuthPrecision=2) const override
	returns a string representation of the ellipse.

Public Member Functions inherited from QgsEllipse
	QgsEllipse ()=default
	Constructor for QgsEllipse.

	QgsEllipse (const QgsPoint &center, double semiMajorAxis, double semiMinorAxis, double azimuth=90)
	Constructs an ellipse by defining all the members.

virtual	~QgsEllipse ()=default

double	azimuth () const
	Returns the azimuth.

QgsPoint	center () const
	Returns the center point.

virtual double	eccentricity () const
	The eccentricity of the ellipse.

virtual QVector< QgsPoint >	foci () const
	Two foci of the ellipse.

virtual double	focusDistance () const
	The distance between the center and each foci.

virtual bool	isEmpty () const
	An ellipse is empty if axes are equal to 0.

virtual bool	operator!= (const QgsEllipse &elp) const

virtual bool	operator== (const QgsEllipse &elp) const

virtual QgsPolygon *	orientedBoundingBox () const
	Returns the oriented minimal bounding box for the ellipse.

virtual QgsPointSequence	points (unsigned int segments=36) const
	Returns a list of points with segmentation from segments.

virtual QVector< QgsPoint >	quadrant () const
	The four quadrants of the ellipse.

QgsPoint &	rcenter ()
	Returns a reference to the center point of this ellipse.

double	semiMajorAxis () const
	Returns the semi-major axis.

double	semiMinorAxis () const
	Returns the semi-minor axis.

void	setAzimuth (double azimuth)
	Sets the azimuth (orientation).

void	setCenter (const QgsPoint &center)
	Sets the center point.

virtual QgsLineString *	toLineString (unsigned int segments=36) const
	Returns a segmented linestring.

virtual QgsPolygon *	toPolygon (unsigned int segments=36) const
	Returns a segmented polygon.

Static Public Member Functions
static QgsCircle	from2Points (const QgsPoint &pt1, const QgsPoint &pt2)
	Constructs a circle by 2 points on the circle.

static QgsCircle	from3Points (const QgsPoint &pt1, const QgsPoint &pt2, const QgsPoint &pt3, double epsilon=1E-8)
	Constructs a circle by 3 points on the circle.

static QgsCircle	from3Tangents (const QgsPoint &pt1_tg1, const QgsPoint &pt2_tg1, const QgsPoint &pt1_tg2, const QgsPoint &pt2_tg2, const QgsPoint &pt1_tg3, const QgsPoint &pt2_tg3, double epsilon=1E-8, const QgsPoint &pos=QgsPoint())
	Constructs a circle by 3 tangents on the circle (aka inscribed circle of a triangle).

static QVector< QgsCircle >	from3TangentsMulti (const QgsPoint &pt1_tg1, const QgsPoint &pt2_tg1, const QgsPoint &pt1_tg2, const QgsPoint &pt2_tg2, const QgsPoint &pt1_tg3, const QgsPoint &pt2_tg3, double epsilon=1E-8, const QgsPoint &pos=QgsPoint())
	Returns an array of circle constructed by 3 tangents on the circle (aka inscribed circle of a triangle).

static QgsCircle	fromCenterDiameter (const QgsPoint &center, double diameter, double azimuth=0)
	Constructs a circle by a center point and a diameter.

static QgsCircle	fromCenterPoint (const QgsPoint &center, const QgsPoint &pt1)
	Constructs a circle by a center point and another point.

static QgsCircle	fromExtent (const QgsPoint &pt1, const QgsPoint &pt2)
	Constructs a circle by an extent (aka bounding box / QgsRectangle).

static QgsCircle	minimalCircleFrom3Points (const QgsPoint &pt1, const QgsPoint &pt2, const QgsPoint &pt3, double epsilon=1E-8)
	Constructs the smallest circle from 3 points.

Static Public Member Functions inherited from QgsEllipse
static QgsEllipse	fromCenter2Points (const QgsPoint &ptc, const QgsPoint &pt1, const QgsPoint &pt2)
	Constructs an ellipse by a central point and two other points.

static QgsEllipse	fromCenterPoint (const QgsPoint &ptc, const QgsPoint &pt1)
	Constructs an ellipse by a center point and a another point.

static QgsEllipse	fromExtent (const QgsPoint &pt1, const QgsPoint &pt2)
	Constructs an ellipse by an extent (aka bounding box / QgsRectangle).

static QgsEllipse	fromFoci (const QgsPoint &pt1, const QgsPoint &pt2, const QgsPoint &pt3)
	Constructs an ellipse by foci (pt1 and pt2) and a point pt3.

Additional Inherited Members
Protected Attributes inherited from QgsEllipse
double	mAzimuth = 90.0

QgsPoint	mCenter

double	mSemiMajorAxis = 0.0

double	mSemiMinorAxis = 0.0

Detailed Description

Circle geometry type.

A circle is defined by a center point with a radius and an azimuth. The azimuth is the north angle to the semi-major axis, in degrees. By default, the semi-major axis is oriented to the north (0 degrees).

Definition at line 42 of file qgscircle.h.

Constructor & Destructor Documentation

◆ QgsCircle() [1/2]

QgsCircle::QgsCircle ( )

Definition at line 26 of file qgscircle.cpp.

◆ QgsCircle() [2/2]

QgsCircle::QgsCircle	(	const QgsPoint &	center,
		double	radius,
		double	azimuth = `0`
	)

Constructs a circle by defining all the members.

Parameters

center	The center of the circle.
radius	The radius of the circle.
azimuth	Angle in degrees started from the North to the first quadrant.

Definition at line 32 of file qgscircle.cpp.

Member Function Documentation

◆ area()

double QgsCircle::area ( ) const

overridevirtual

The area of the ellipse.

Reimplemented from QgsEllipse.

Definition at line 397 of file qgscircle.cpp.

◆ asGml2()

QDomElement QgsCircle::asGml2	(	QDomDocument &	doc,
		int	precision = `17`,
		const QString &	ns = `"gml"`,
		QgsAbstractGeometry::AxisOrder	axisOrder = `QgsAbstractGeometry::AxisOrder::XY`
	)		const

Returns a GML2 representation of the geometry.

Since GML2 does not supports curve, it will be converted to a LineString.

Parameters

doc	DOM document
precision	number of decimal places for coordinates
ns	XML namespace
axisOrder	Axis order for generated GML

See also: asGml3()

Definition at line 478 of file qgscircle.cpp.

◆ asGml3()

QDomElement QgsCircle::asGml3	(	QDomDocument &	doc,
		int	precision = `17`,
		const QString &	ns = `"gml"`,
		QgsAbstractGeometry::AxisOrder	axisOrder = `QgsAbstractGeometry::AxisOrder::XY`
	)		const

Returns a GML3 representation of the geometry.

From the GML3 description: A Circle is an arc whose ends coincide to form a simple closed loop. The three control points shall be distinct non-co-linear points for the circle to be unambiguously defined. The arc is simply extended past the third control point until the first control point is encountered.

Coordinates are taken from quadrant North, East and South.

Parameters

doc	DOM document
precision	number of decimal places for coordinates
ns	XML namespace
axisOrder	Axis order for generated GML

See also: asGml2()

Definition at line 486 of file qgscircle.cpp.

◆ boundingBox()

QgsRectangle QgsCircle::boundingBox ( ) const

overridevirtual

Returns the minimal bounding box for the ellipse.

Reimplemented from QgsEllipse.

Definition at line 458 of file qgscircle.cpp.

◆ contains()

bool QgsCircle::contains	(	const QgsPoint &	point,
		double	epsilon = `1E-8`
	)		const

Returns true if the circle contains the point.

Definition at line 453 of file qgscircle.cpp.

◆ from2Points()

QgsCircle QgsCircle::from2Points	(	const QgsPoint &	pt1,
		const QgsPoint &	pt2
	)

static

Constructs a circle by 2 points on the circle.

The center point can have m value which is the result from the midpoint operation between pt1 and pt2. Z dimension is also supported and is retrieved from the first 3D point amongst pt1 and pt2. The radius is calculated from the 2D distance between pt1 and pt2. The azimuth is the angle between pt1 and pt2.

Parameters

pt1	First point.
pt2	Second point.

Definition at line 38 of file qgscircle.cpp.

◆ from3Points()

QgsCircle QgsCircle::from3Points	(	const QgsPoint &	pt1,
		const QgsPoint &	pt2,
		const QgsPoint &	pt3,
		double	epsilon = `1E-8`
	)

static

Constructs a circle by 3 points on the circle.

M value is dropped for the center point. Z dimension is supported and is retrieved from the first 3D point amongst pt1, pt2 and pt3. The azimuth always takes the default value. If the points are colinear an empty circle is returned.

Parameters

pt1	First point.
pt2	Second point.
pt3	Third point.
epsilon	Value used to compare point.

Definition at line 84 of file qgscircle.cpp.

◆ from3Tangents()

QgsCircle QgsCircle::from3Tangents	(	const QgsPoint &	pt1_tg1,
		const QgsPoint &	pt2_tg1,
		const QgsPoint &	pt1_tg2,
		const QgsPoint &	pt2_tg2,
		const QgsPoint &	pt1_tg3,
		const QgsPoint &	pt2_tg3,
		double	epsilon = `1E-8`,
		const QgsPoint &	pos = `QgsPoint()`
	)

static

Constructs a circle by 3 tangents on the circle (aka inscribed circle of a triangle).

Z and m values are dropped for the center point. The azimuth always takes the default value.

Parameters

pt1_tg1	First point of the first tangent.
pt2_tg1	Second point of the first tangent.
pt1_tg2	First point of the second tangent.
pt2_tg2	Second point of the second tangent.
pt1_tg3	First point of the third tangent.
pt2_tg3	Second point of the third tangent.
epsilon	Value used to compare point.
pos	Point to determine which circle use in case of multi return. If the solution is not unique and pos is an empty point, an empty circle is returned. – This case happens only when two tangents are parallels. (since QGIS 3.18)

See also: from3TangentsMulti()

Example

# [(0 0), (5 0)] and [(5 5), (10 5)] are parallels
QgsCircle.from3Tangents(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5))
# <QgsCircle: Empty>
QgsCircle.from3Tangents(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5), pos=QgsPoint(2, 0))
# <QgsCircle: Circle (Center: Point (1.46446609406726203 2.49999999999999911), Radius: 2.5, Azimuth: 0)>
QgsCircle.from3Tangents(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5), pos=QgsPoint(3, 0))
# <QgsCircle: Circle (Center: Point (8.53553390593273775 2.5), Radius: 2.5, Azimuth: 0)>

Definition at line 318 of file qgscircle.cpp.

◆ from3TangentsMulti()

QVector< QgsCircle > QgsCircle::from3TangentsMulti	(	const QgsPoint &	pt1_tg1,
		const QgsPoint &	pt2_tg1,
		const QgsPoint &	pt1_tg2,
		const QgsPoint &	pt2_tg2,
		const QgsPoint &	pt1_tg3,
		const QgsPoint &	pt2_tg3,
		double	epsilon = `1E-8`,
		const QgsPoint &	pos = `QgsPoint()`
	)

static

Returns an array of circle constructed by 3 tangents on the circle (aka inscribed circle of a triangle).

The vector can contain 0, 1 or 2 circles:

0: Impossible to construct a circle from 3 tangents (three parallel tangents)
1: The three tangents make a triangle or when two tangents are parallel there are two possible circles (see examples). If pos is not an empty point, we use its coordinates to determine which circle will be returned. More precisely the circle that will be returned will be the one whose center is on the same side as pos relative to the third tangent.
2: Returns both solutions when two tangents are parallel (this implies that pos is an empty point).

Z and m values are dropped for the center point. The azimuth always takes the default value.

Parameters

pt1_tg1	First point of the first tangent.
pt2_tg1	Second point of the first tangent.
pt1_tg2	First point of the second tangent.
pt2_tg2	Second point of the second tangent.
pt1_tg3	First point of the third tangent.
pt2_tg3	Second point of the third tangent.
epsilon	Value used to compare point.
pos	(optional) Point to determine which circle use in case of multi return.

See also: from3Tangents()

Example

# [(0 0), (5 0)] and [(5 5), (10 5)] are parallels
QgsCircle.from3TangentsMulti(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5))
# [<QgsCircle: Circle (Center: Point (8.53553390593273775 2.5), Radius: 2.5, Azimuth: 0)>, <QgsCircle: Circle (Center: Point (1.46446609406726203 2.49999999999999911), Radius: 2.5, Azimuth: 0)>]
QgsCircle.from3TangentsMulti(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5), pos=QgsPoint(2, 0))
# [<QgsCircle: Circle (Center: Point (1.46446609406726203 2.49999999999999911), Radius: 2.5, Azimuth: 0)>]
QgsCircle.from3TangentsMulti(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(2.5, 0), QgsPoint(7.5, 5), pos=QgsPoint(3, 0))
# [<QgsCircle: Circle (Center: Point (8.53553390593273775 2.5), Radius: 2.5, Azimuth: 0)>]
# [(0 0), (5 0)], [(5 5), (10 5)] and [(15 5), (20 5)] are parallels
QgsCircle.from3TangentsMulti(QgsPoint(0, 0), QgsPoint(5, 0), QgsPoint(5, 5), QgsPoint(10, 5), QgsPoint(15, 5), QgsPoint(20, 5))
# []

Definition at line 278 of file qgscircle.cpp.

◆ fromCenterDiameter()

QgsCircle QgsCircle::fromCenterDiameter	(	const QgsPoint &	center,
		double	diameter,
		double	azimuth = `0`
	)

static

Constructs a circle by a center point and a diameter.

The center point keeps z and m values from center.

Parameters

center	Center point.
diameter	Diameter of the circle.
azimuth	Azimuth of the circle.

Definition at line 177 of file qgscircle.cpp.

◆ fromCenterPoint()

QgsCircle QgsCircle::fromCenterPoint	(	const QgsPoint &	center,
		const QgsPoint &	pt1
	)

static

Constructs a circle by a center point and another point.

The center point keeps z and m values from center. Axes are calculated from the 2D distance between center and pt1. The azimuth is the angle between center and pt1.

Parameters

center	Center point.
pt1	A point on the circle.

Definition at line 182 of file qgscircle.cpp.

◆ fromExtent()

QgsCircle QgsCircle::fromExtent	(	const QgsPoint &	pt1,
		const QgsPoint &	pt2
	)

static

Constructs a circle by an extent (aka bounding box / QgsRectangle).

The center point can have m value which is the result from the midpoint operation between pt1 and pt2. Z dimension is also supported and is retrieved from the first 3D point amongst pt1 and pt2. Axes are calculated from the 2D distance between pt1 and pt2. The azimuth always takes the default value.

Parameters

pt1	First corner.
pt2	Second corner.

Definition at line 382 of file qgscircle.cpp.

◆ innerTangents()

int QgsCircle::innerTangents	(	const QgsCircle &	other,
		QgsPointXY &	line1P1,
		QgsPointXY &	line1P2,
		QgsPointXY &	line2P1,
		QgsPointXY &	line2P2
	)		const

Calculates the inner tangent points between this circle and an other circle.

The inner tangent points correspond to the points at which the two lines which are drawn so that they are tangential to both circles but on different sides, touching the circles and crossing each other.

The first tangent line is described by the points stored in line1P1 and line1P2, and the second line is described by the points stored in line2P1 and line2P2.

Returns the number of tangents (either 0 or 2).

Note: This method is 2D only and does not consider the z-value of the circle.

See also: tangentToPoint(); outerTangents()

Since: QGIS 3.6

Definition at line 376 of file qgscircle.cpp.

◆ intersections()

int QgsCircle::intersections	(	const QgsCircle &	other,
		QgsPoint &	intersection1,
		QgsPoint &	intersection2,
		bool	useZ = `false`
	)		const

Calculates the intersections points between this circle and an other circle.

If found, the intersection points will be stored in intersection1 and intersection2.

By default this method does not consider any z values and instead treats the circles as 2-dimensional. If useZ is set to true, then an intersection will only occur if the z values of both circles are equal. In this case the points returned for intersection1 and intersection2 will contain the z value of the circle intersections.

Returns: number of intersection points found.

Since: QGIS 3.2

Definition at line 342 of file qgscircle.cpp.

◆ minimalCircleFrom3Points()

QgsCircle QgsCircle::minimalCircleFrom3Points	(	const QgsPoint &	pt1,
		const QgsPoint &	pt2,
		const QgsPoint &	pt3,
		double	epsilon = `1E-8`
	)

static

Constructs the smallest circle from 3 points.

Z and m values are dropped for the center point. The azimuth always takes the default value. If the points are colinear an empty circle is returned.

Parameters

pt1	First point.
pt2	Second point.
pt3	Third point.
epsilon	Value used to compare point.

Definition at line 326 of file qgscircle.cpp.

◆ northQuadrant()

QVector< QgsPoint > QgsCircle::northQuadrant ( ) const

The four quadrants of the ellipse.

They are oriented and started from North.

Returns: quadrants defined by four points.

See also: quadrant()

Definition at line 419 of file qgscircle.cpp.

◆ outerTangents()

int QgsCircle::outerTangents	(	const QgsCircle &	other,
		QgsPointXY &	line1P1,
		QgsPointXY &	line1P2,
		QgsPointXY &	line2P1,
		QgsPointXY &	line2P2
	)		const

Calculates the outer tangent points between this circle and an other circle.

The outer tangent points correspond to the points at which the two lines which are drawn so that they are tangential to both circles touch the circles.

The first tangent line is described by the points stored in line1P1 and line1P2, and the second line is described by the points stored in line2P1 and line2P2.

Returns the number of tangents (either 0 or 2).

Note: This method is 2D only and does not consider the z-value of the circle.

See also: tangentToPoint(); innerTangents()

Since: QGIS 3.2

Definition at line 370 of file qgscircle.cpp.

◆ perimeter()

double QgsCircle::perimeter ( ) const

overridevirtual

The circumference of the ellipse using first approximation of Ramanujan.

Reimplemented from QgsEllipse.

Definition at line 402 of file qgscircle.cpp.

◆ radius()

double QgsCircle::radius ( ) const

inline

Returns the radius of the circle.

Definition at line 310 of file qgscircle.h.

◆ setRadius()

void QgsCircle::setRadius ( double radius )

inline

Sets the radius of the circle.

Definition at line 312 of file qgscircle.h.

◆ setSemiMajorAxis()

void QgsCircle::setSemiMajorAxis ( double semiMajorAxis )

overridevirtual

Inherited method.

Use setRadius() instead.

See also: radius(); setRadius()

Reimplemented from QgsEllipse.

Definition at line 407 of file qgscircle.cpp.

◆ setSemiMinorAxis()

void QgsCircle::setSemiMinorAxis ( double semiMinorAxis )

overridevirtual

Inherited method.

Use setRadius() instead.

See also: radius(); setRadius()

Reimplemented from QgsEllipse.

Definition at line 413 of file qgscircle.cpp.

◆ tangentToPoint()

bool QgsCircle::tangentToPoint	(	const QgsPointXY &	p,
		QgsPointXY &	pt1,
		QgsPointXY &	pt2
	)		const

Calculates the tangent points between this circle and the point p.

If found, the tangent points will be stored in pt1 and pt2.

Note: This method is 2D only and does not consider the z-value of the circle.

Returns: true if tangent was found.

See also: outerTangents(); innerTangents()

Since: QGIS 3.2

Definition at line 365 of file qgscircle.cpp.

◆ toCircularString()

QgsCircularString * QgsCircle::toCircularString ( bool oriented = false ) const

Returns a circular string from the circle.

Parameters

oriented If oriented is true the start point is from azimuth instead from north.

Definition at line 430 of file qgscircle.cpp.

◆ toString()

QString QgsCircle::toString	(	int	pointPrecision = `17`,
		int	axisPrecision = `17`,
		int	azimuthPrecision = `2`
	)		const

overridevirtual

returns a string representation of the ellipse.

Members will be truncated to the specified precision.

Reimplemented from QgsEllipse.

Definition at line 463 of file qgscircle.cpp.

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

/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/geometry/qgscircle.h
/build/qgis-3.41.0+git20241225+af5edcb665c+99sid/src/core/geometry/qgscircle.cpp

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ QgsCircle() [1/2]

◆ QgsCircle() [2/2]

Member Function Documentation

◆ area()

◆ asGml2()

◆ asGml3()

◆ boundingBox()

◆ contains()

◆ from2Points()

◆ from3Points()

◆ from3Tangents()

Example

◆ from3TangentsMulti()

Example

◆ fromCenterDiameter()

◆ fromCenterPoint()

◆ fromExtent()

◆ innerTangents()

◆ intersections()

◆ minimalCircleFrom3Points()

◆ northQuadrant()

◆ outerTangents()

◆ perimeter()

◆ radius()

◆ setRadius()

◆ setSemiMajorAxis()

◆ setSemiMinorAxis()

◆ tangentToPoint()

◆ toCircularString()

◆ toString()