Class for doing transforms between two map coordinate systems. More...

#include <qgscoordinatetransform.h>

Public Types
enum	TransformDirection { ForwardTransform, ReverseTransform }
	Enum used to indicate the direction (forward or inverse) of the transform. More...

Public Member Functions
	QgsCoordinateTransform ()
	Default constructor, creates an invalid QgsCoordinateTransform. More...

Q_DECL_DEPRECATED	QgsCoordinateTransform (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination)
	Constructs a QgsCoordinateTransform using QgsCoordinateReferenceSystem objects. More...

	QgsCoordinateTransform (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination, const QgsCoordinateTransformContext &context)
	Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system. More...

	QgsCoordinateTransform (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination, const QgsProject *project)
	Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system, when used with the given project. More...

	QgsCoordinateTransform (const QgsCoordinateReferenceSystem &source, const QgsCoordinateReferenceSystem &destination, int sourceDatumTransformId, int destinationDatumTransformId)
	Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system, with the specified datum transforms (see QgsDatumTransform). More...

	QgsCoordinateTransform (const QgsCoordinateTransform &o)
	Copy constructor. More...

	~QgsCoordinateTransform ()

QgsCoordinateTransformContext	context () const
	Returns the context in which the coordinate transform will be calculated. More...

QgsCoordinateReferenceSystem	destinationCrs () const
	Returns the destination coordinate reference system, which the transform will transform coordinates to. More...

int	destinationDatumTransformId () const
	Returns the ID of the datum transform to use when projecting to the destination CRS. More...

bool	isShortCircuited () const
	Returns true if the transform short circuits because the source and destination are equivalent. More...

bool	isValid () const
	Returns true if the coordinate transform is valid, ie both the source and destination CRS have been set and are valid. More...

QgsCoordinateTransform &	operator= (const QgsCoordinateTransform &o)
	Assignment operator. More...

double	scaleFactor (const QgsRectangle &referenceExtent) const
	Computes an estimated conversion factor between source and destination units: More...

void	setContext (const QgsCoordinateTransformContext &context)
	Sets the context in which the coordinate transform should be calculated. More...

void	setDestinationCrs (const QgsCoordinateReferenceSystem &crs)
	Sets the destination coordinate reference system. More...

void	setDestinationDatumTransformId (int datumId)
	Sets the datumId ID of the datum transform to use when projecting to the destination CRS. More...

void	setSourceCrs (const QgsCoordinateReferenceSystem &crs)
	Sets the source coordinate reference system. More...

void	setSourceDatumTransformId (int datumId)
	Sets the datumId ID of the datum transform to use when projecting from the source CRS. More...

QgsCoordinateReferenceSystem	sourceCrs () const
	Returns the source coordinate reference system, which the transform will transform coordinates from. More...

int	sourceDatumTransformId () const
	Returns the ID of the datum transform to use when projecting from the source CRS. More...

QgsPointXY	transform (const QgsPointXY &point, TransformDirection direction=ForwardTransform) const SIP_THROW(QgsCsException)
	Transform the point from the source CRS to the destination CRS. More...

QgsPointXY	transform (double x, double y, TransformDirection direction=ForwardTransform) const
	Transform the point specified by x,y from the source CRS to the destination CRS. More...

QgsRectangle	transform (const QgsRectangle &rectangle, TransformDirection direction=ForwardTransform) const SIP_THROW(QgsCsException)
	Transforms a rectangle to the destination CRS. More...

QgsRectangle	transformBoundingBox (const QgsRectangle &rectangle, TransformDirection direction=ForwardTransform, bool handle180Crossover=false) const SIP_THROW(QgsCsException)
	Transforms a rectangle from the source CRS to the destination CRS. More...

void	transformCoords (int numPoint, double x, double y, double *z, TransformDirection direction=ForwardTransform) const SIP_THROW(QgsCsException)
	Transform an array of coordinates to the destination CRS. More...

void	transformInPlace (double &x, double &y, double &z, TransformDirection direction=ForwardTransform) const SIP_THROW(QgsCsException)
	Transforms an array of x, y and z double coordinates in place, from the source CRS to the destination CRS. More...

void	transformInPlace (float &x, float &y, double &z, TransformDirection direction=ForwardTransform) const
	Transforms an array of x, y and z float coordinates in place, from the source CRS to the destination CRS. More...

void	transformInPlace (float &x, float &y, float &z, TransformDirection direction=ForwardTransform) const
	Transforms an array of x, y and z float coordinates in place, from the source CRS to the destination CRS. More...

void	transformInPlace (QVector< float > &x, QVector< float > &y, QVector< float > &z, TransformDirection direction=ForwardTransform) const
	Transforms a vector of x, y and z float coordinates in place, from the source CRS to the destination CRS. More...

void	transformInPlace (QVector< double > &x, QVector< double > &y, QVector< double > &z, TransformDirection direction=ForwardTransform) const
	Transforms a vector of x, y and z double coordinates in place, from the source CRS to the destination CRS. More...

void	transformPolygon (QPolygonF &polygon, TransformDirection direction=ForwardTransform) const SIP_THROW(QgsCsException)
	Transforms a polygon to the destination coordinate system. More...

Static Public Member Functions
static void	invalidateCache (bool disableCache=false)
	Clears the internal cache used to initialize QgsCoordinateTransform objects. More...

Detailed Description

Class for doing transforms between two map coordinate systems.

This class can convert map coordinates to a different coordinate reference system. It is normally associated with a map layer and is used to transform between the layer's coordinate system and the coordinate system of the map canvas, although it can be used in a more general sense to transform coordinates.

When used to transform between a layer and the map canvas, all references to source and destination coordinate systems refer to layer and map canvas respectively. All operations are from the perspective of the layer. For example, a forward transformation transforms coordinates from the layer's coordinate system to the map canvas.

Note: Since QGIS 3.0 QgsCoordinateReferenceSystem objects are implicitly shared.

See also: QgsDatumTransform; QgsCoordinateTransformContext

Definition at line 52 of file qgscoordinatetransform.h.

Member Enumeration Documentation

enum QgsCoordinateTransform::TransformDirection

Enum used to indicate the direction (forward or inverse) of the transform.

Enumerator
ForwardTransform	Transform from source to destination CRS.
ReverseTransform	Transform from destination to source CRS.

Definition at line 58 of file qgscoordinatetransform.h.

Constructor & Destructor Documentation

QgsCoordinateTransform::QgsCoordinateTransform ( )

Default constructor, creates an invalid QgsCoordinateTransform.

Definition at line 52 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::QgsCoordinateTransform	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination
	)

explicit

Constructs a QgsCoordinateTransform using QgsCoordinateReferenceSystem objects.

Parameters

source	source CRS, typically of the layer's coordinate system
destination	CRS, typically of the map canvas coordinate system correctly handle the user's datum transform setup. Instead the constructor variant which accepts a QgsCoordinateTransformContext or QgsProject argument should be used instead. It is highly likely that this constructor will be removed in future QGIS versions.

Note: Not available in Python bindings.

Deprecated:: Use of this constructor is strongly discouraged, as it will not

Definition at line 57 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::QgsCoordinateTransform	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination,
		const QgsCoordinateTransformContext &	context
	)

explicit

Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system.

The context argument specifies the context under which the transform will be applied, and is used for calculating necessary datum transforms to utilize.

Python scripts should generally use the constructor variant which accepts a QgsProject instance instead of this constructor.

Warning: Do NOT use an empty/default constructed QgsCoordinateTransformContext() object when creating QgsCoordinateTransform objects. This prevents correct datum transform handling and may result in inaccurate transformations. Always ensure that the QgsCoordinateTransformContext object is correctly retrieved based on the current code context, or use the constructor variant which accepts a QgsProject argument instead.

Since: QGIS 3.0

Definition at line 71 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::QgsCoordinateTransform	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination,
		const QgsProject *	project
	)

explicit

Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system, when used with the given project.

No reference to project is stored or utilized outside of the constructor, and it is used to retrieve the project's transform context only.

Python scripts should utilize the QgsProject.instance() project instance when creating QgsCoordinateTransform. This will ensure that any datum transforms defined in the project will be correctly respected during coordinate transforms. E.g.

1 transform = QgsCoordinateTransform(QgsCoordinateReferenceSystem("EPSG:3111"),

2 QgsCoordinateReferenceSystem("EPSG:4326"), QgsProject.instance())

Since: QGIS 3.0

Definition at line 89 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::QgsCoordinateTransform	(	const QgsCoordinateReferenceSystem &	source,
		const QgsCoordinateReferenceSystem &	destination,
		int	sourceDatumTransformId,
		int	destinationDatumTransformId
	)

explicit

Constructs a QgsCoordinateTransform to transform from the source to destination coordinate reference system, with the specified datum transforms (see QgsDatumTransform).

Since: QGIS 3.0

Definition at line 108 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::QgsCoordinateTransform ( const QgsCoordinateTransform & o )

Copy constructor.

Definition at line 125 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform::~QgsCoordinateTransform ( )

Definition at line 144 of file qgscoordinatetransform.cpp.

Member Function Documentation

QgsCoordinateTransformContext QgsCoordinateTransform::context ( ) const

Returns the context in which the coordinate transform will be calculated.

See also: setContext()

Since: QGIS 3.4

Definition at line 193 of file qgscoordinatetransform.cpp.

QgsCoordinateReferenceSystem QgsCoordinateTransform::destinationCrs ( ) const

Returns the destination coordinate reference system, which the transform will transform coordinates to.

See also: setDestinationCrs(); sourceCrs()

Definition at line 203 of file qgscoordinatetransform.cpp.

int QgsCoordinateTransform::destinationDatumTransformId ( ) const

Returns the ID of the datum transform to use when projecting to the destination CRS.

This is usually calculated automatically from the transform's QgsCoordinateTransformContext, but can be manually overwritten by a call to setDestinationDatumTransformId().

See also: QgsDatumTransform; setDestinationDatumTransformId(); sourceDatumTransformId()

Definition at line 808 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::invalidateCache ( bool disableCache = false )

static

Clears the internal cache used to initialize QgsCoordinateTransform objects.

This should be called whenever the srs database has been modified in order to ensure that outdated CRS transforms are not created.

If disableCache is TRUE then the inbuilt cache will be completely disabled. This argument is for internal use only.

Since: QGIS 3.0

Definition at line 819 of file qgscoordinatetransform.cpp.

bool QgsCoordinateTransform::isShortCircuited ( ) const

Returns true if the transform short circuits because the source and destination are equivalent.

Definition at line 718 of file qgscoordinatetransform.cpp.

bool QgsCoordinateTransform::isValid ( ) const

Returns true if the coordinate transform is valid, ie both the source and destination CRS have been set and are valid.

Since: QGIS 3.0

Definition at line 713 of file qgscoordinatetransform.cpp.

QgsCoordinateTransform & QgsCoordinateTransform::operator= ( const QgsCoordinateTransform & o )

Assignment operator.

Definition at line 134 of file qgscoordinatetransform.cpp.

double QgsCoordinateTransform::scaleFactor ( const QgsRectangle & referenceExtent ) const

Computes an estimated conversion factor between source and destination units:

sourceUnits * scaleFactor = destinationUnits

Parameters

referenceExtent A reference extent based on which to perform the computation

Since: QGIS 3.4

Definition at line 833 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::setContext ( const QgsCoordinateTransformContext & context )

Sets the context in which the coordinate transform should be calculated.

See also: context()

Since: QGIS 3.0

Definition at line 175 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::setDestinationCrs ( const QgsCoordinateReferenceSystem & crs )

Sets the destination coordinate reference system.

Parameters

crs	CRS to transform coordinates to

See also: destinationCrs(); setSourceCrs()

Definition at line 160 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::setDestinationDatumTransformId ( int datumId )

Sets the datumId ID of the datum transform to use when projecting to the destination CRS.

This is usually calculated automatically from the transform's QgsCoordinateTransformContext. Calling this method will overwrite any automatically calculated datum transform.

See also: QgsDatumTransform; destinationDatumTransformId(); setSourceDatumTransformId()

Definition at line 813 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::setSourceCrs ( const QgsCoordinateReferenceSystem & crs )

Sets the source coordinate reference system.

Parameters

crs	CRS to transform coordinates from

See also: sourceCrs(); setDestinationCrs()

Definition at line 146 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::setSourceDatumTransformId ( int datumId )

Sets the datumId ID of the datum transform to use when projecting from the source CRS.

This is usually calculated automatically from the transform's QgsCoordinateTransformContext. Calling this method will overwrite any automatically calculated datum transform.

See also: QgsDatumTransform; sourceDatumTransformId(); setDestinationDatumTransformId()

Definition at line 802 of file qgscoordinatetransform.cpp.

QgsCoordinateReferenceSystem QgsCoordinateTransform::sourceCrs ( ) const

Returns the source coordinate reference system, which the transform will transform coordinates from.

See also: setSourceCrs(); destinationCrs()

Definition at line 198 of file qgscoordinatetransform.cpp.

int QgsCoordinateTransform::sourceDatumTransformId ( ) const

Returns the ID of the datum transform to use when projecting from the source CRS.

This is usually calculated automatically from the transform's QgsCoordinateTransformContext, but can be manually overwritten by a call to setSourceDatumTransformId().

See also: QgsDatumTransform; setSourceDatumTransformId(); destinationDatumTransformId()

Definition at line 797 of file qgscoordinatetransform.cpp.

QgsPointXY QgsCoordinateTransform::transform	(	const QgsPointXY &	point,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transform the point from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

point	point to transform
direction	transform direction (defaults to ForwardTransform)

Returns: transformed point

Definition at line 208 of file qgscoordinatetransform.cpp.

QgsPointXY QgsCoordinateTransform::transform	(	double	x,
		double	y = `0.0`,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transform the point specified by x,y from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	x coordinate of point to transform
y	y coordinate of point to transform
direction	transform direction (defaults to ForwardTransform)

Returns: transformed point

Definition at line 232 of file qgscoordinatetransform.cpp.

QgsRectangle QgsCoordinateTransform::transform	(	const QgsRectangle &	rectangle,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms a rectangle to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

rectangle	rectangle to transform
direction	transform direction (defaults to ForwardTransform)

Returns: transformed rectangle

Definition at line 246 of file qgscoordinatetransform.cpp.

QgsRectangle QgsCoordinateTransform::transformBoundingBox	(	const QgsRectangle &	rectangle,
		TransformDirection	direction = `ForwardTransform`,
		bool	handle180Crossover = `false`
	)		const

Transforms a rectangle from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS. This method assumes that the rectangle is a bounding box, and creates a bounding box in the projected CRS, such that all points from the source rectangle are within the returned rectangle.

Parameters

rectangle	rectangle to transform
direction	transform direction (defaults to ForwardTransform)
handle180Crossover	set to true if destination CRS is geographic and handling of extents crossing the 180 degree longitude line is required

Returns: rectangle in destination CRS

Definition at line 476 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformCoords	(	int	numPoint,
		double *	x,
		double *	y,
		double *	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transform an array of coordinates to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

numPoint	number of coordinates in arrays
x	array of x coordinates to transform
y	array of y coordinates to transform
z	array of z coordinates to transform
direction	transform direction (defaults to ForwardTransform)

Definition at line 595 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformInPlace	(	double &	x,
		double &	y,
		double &	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms an array of x, y and z double coordinates in place, from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	array of x coordinates of points to transform
y	array of y coordinates of points to transform
z	array of z coordinates of points to transform. The z coordinates of the points must represent height relative to the vertical datum of the source CRS (generally ellipsoidal heights) and must be expressed in its vertical units (generally meters)
direction	transform direction (defaults to ForwardTransform)

Definition at line 282 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformInPlace	(	float &	x,
		float &	y,
		double &	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms an array of x, y and z float coordinates in place, from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	array of x coordinates of points to transform
y	array of y coordinates of points to transform
z	array of z coordinates of points to transform. The z coordinates of the points must represent height relative to the vertical datum of the source CRS (generally ellipsoidal heights) and must be expressed in its vertical units (generally meters)
direction	transform direction (defaults to ForwardTransform)

Note: not available in Python bindings

Definition at line 303 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformInPlace	(	float &	x,
		float &	y,
		float &	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms an array of x, y and z float coordinates in place, from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	array of x coordinates of points to transform
y	array of y coordinates of points to transform
z	array of z coordinates of points to transform. The z coordinates of the points must represent height relative to the vertical datum of the source CRS (generally ellipsoidal heights) and must be expressed in its vertical units (generally meters)
direction	transform direction (defaults to ForwardTransform)

Note: not available in Python bindings

Definition at line 312 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformInPlace	(	QVector< float > &	x,
		QVector< float > &	y,
		QVector< float > &	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms a vector of x, y and z float coordinates in place, from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	vector of x coordinates of points to transform
y	vector of y coordinates of points to transform
z	vector of z coordinates of points to transform. The z coordinates of the points must represent height relative to the vertical datum of the source CRS (generally ellipsoidal heights) and must be expressed in its vertical units (generally meters)
direction	transform direction (defaults to ForwardTransform)

Note: not available in Python bindings

Definition at line 415 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformInPlace	(	QVector< double > &	x,
		QVector< double > &	y,
		QVector< double > &	z,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms a vector of x, y and z double coordinates in place, from the source CRS to the destination CRS.

If the direction is ForwardTransform then coordinates are transformed from source to destination, otherwise points are transformed from destination to source CRS.

Parameters

x	vector of x coordinates of points to transform
y	vector of y coordinates of points to transform
z	vector of z coordinates of points to transform. The z coordinates of the points must represent height relative to the vertical datum of the source CRS (generally ellipsoidal heights) and must be expressed in its vertical units (generally meters)
direction	transform direction (defaults to ForwardTransform)

Note: not available in Python bindings

Definition at line 387 of file qgscoordinatetransform.cpp.

void QgsCoordinateTransform::transformPolygon	(	QPolygonF &	polygon,
		TransformDirection	direction = `ForwardTransform`
	)		const

Transforms a polygon to the destination coordinate system.

Parameters

polygon	polygon to transform (occurs in place)
direction	transform direction (defaults to forward transformation)

Definition at line 339 of file qgscoordinatetransform.cpp.

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

/build/qgis-3.4.15+24xenial/src/core/qgscoordinatetransform.h
/build/qgis-3.4.15+24xenial/src/core/qgscoordinatetransform.cpp

Public Types

Public Member Functions

Static Public Member Functions

Detailed Description

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation