QgsCoordinateTransform Class Reference

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 Slots
void	initialise ()
	initialise is used to actually create the Transformer instance
bool	readXML (QDomNode &theNode)
bool	writeXML (QDomNode &theNode, QDomDocument &theDoc)

Signals
void	invalidTransformInput () const
	Signal when an invalid pj_transform() has occured.

Public Member Functions
	QgsCoordinateTransform ()
	QgsCoordinateTransform (const QgsCoordinateReferenceSystem &theSource, const QgsCoordinateReferenceSystem &theDest)
	Constructs a QgsCoordinateTransform using QgsCoordinateReferenceSystem objects.
	QgsCoordinateTransform (long theSourceSrsId, long theDestSrsId)
	Constructs a QgsCoordinateTransform using CRS ID of source and destination CRS.
	QgsCoordinateTransform (QString theSourceWkt, QString theDestWkt)
	QgsCoordinateTransform (long theSourceSrid, QString theDestWkt, QgsCoordinateReferenceSystem::CrsType theSourceCRSType=QgsCoordinateReferenceSystem::PostgisCrsId)
	~QgsCoordinateTransform ()
	destructor
QgsCoordinateTransform *	clone () const
void	setSourceCrs (const QgsCoordinateReferenceSystem &theCRS)
void	setDestCRS (const QgsCoordinateReferenceSystem &theCRS)
const QgsCoordinateReferenceSystem &	sourceCrs () const
const QgsCoordinateReferenceSystem &	destCRS () const
QgsPoint	transform (const QgsPoint p, TransformDirection direction=ForwardTransform) const
QgsPoint	transform (const double x, const double y, TransformDirection direction=ForwardTransform) const
QgsRectangle	transformBoundingBox (const QgsRectangle theRect, TransformDirection direction=ForwardTransform, const bool handle180Crossover=false) const
void	transformInPlace (double &x, double &y, double &z, TransformDirection direction=ForwardTransform) const
void	transformInPlace (QVector< double > &x, QVector< double > &y, QVector< double > &z, TransformDirection direction=ForwardTransform) const
void	transformPolygon (QPolygonF &poly, TransformDirection direction=ForwardTransform) const
QgsRectangle	transform (const QgsRectangle theRect, TransformDirection direction=ForwardTransform) const
void	transformCoords (const int &numPoint, double *x, double *y, double *z, TransformDirection direction=ForwardTransform) const
bool	isInitialised () const
bool	isShortCircuited ()
void	setDestCRSID (long theCRSID)
int	sourceDatumTransform () const
void	setSourceDatumTransform (int dt)
int	destinationDatumTransform () const
void	setDestinationDatumTransform (int dt)

Static Public Member Functions
static QList< QList< int > >	datumTransformations (const QgsCoordinateReferenceSystem &srcCRS, const QgsCoordinateReferenceSystem &destCRS)
	Returns list of datum transformations for the given src and dest CRS.
static QString	datumTransformString (int datumTransform)
static bool	datumTransformCrsInfo (int datumTransform, int &epsgNr, QString &srcProjection, QString &dstProjection, QString &remarks, QString &scope, bool &preferred, bool &deprecated)
	Gets name of source and dest geographical CRS (to show in a tooltip)

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.

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 layers coordinate system to the map canvas.

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.

Constructor & Destructor Documentation

QgsCoordinateTransform::QgsCoordinateTransform

(

)

Default constructor. Make sure you use initialised() manually if you use this one!

QgsCoordinateTransform::QgsCoordinateTransform	(	const QgsCoordinateReferenceSystem &	theSource,
		const QgsCoordinateReferenceSystem &	theDest
	)

Constructs a QgsCoordinateTransform using QgsCoordinateReferenceSystem objects.

Parameters

theSource	CRS, typically of the layer's coordinate system
theDest	CRS, typically of the map canvas coordinate system

QgsCoordinateTransform::QgsCoordinateTransform	(	long	theSourceSrsId,
		long	theDestSrsId
	)

Constructs a QgsCoordinateTransform using CRS ID of source and destination CRS.

QgsCoordinateTransform::QgsCoordinateTransform	(	QString	theSourceWkt,
		QString	theDestWkt
	)

Constructs a QgsCoordinateTransform using the Well Known Text representation of the layer and map canvas coordinate systems

Parameters

theSourceWkt	Wkt, typically of the layer's coordinate system
theDestWkt	Wkt, typically of the map canvas coordinate system

QgsCoordinateTransform::QgsCoordinateTransform	(	long	theSourceSrid,
		QString	theDestWkt,
		QgsCoordinateReferenceSystem::CrsType	theSourceCRSType = QgsCoordinateReferenceSystem::PostgisCrsId
	)

Constructs a QgsCoordinateTransform using a Spatial Reference Id of the layer and map canvas coordinate system as Wkt

Parameters

theSourceSrid	Spatial Ref Id of the layer's coordinate system
theDestWkt	Wkt of the map canvas coordinate system
theSourceCRSType	On of the enum members defined in QgsCoordinateReferenceSystem::CrsType

QgsCoordinateTransform::~QgsCoordinateTransform

(

)

destructor

Member Function Documentation

QgsCoordinateTransform * QgsCoordinateTransform::clone

(

)

const

QList< QList< int > > QgsCoordinateTransform::datumTransformations ( const QgsCoordinateReferenceSystem &  srcCRS, const QgsCoordinateReferenceSystem &  destCRS  )

static

Returns list of datum transformations for the given src and dest CRS.

Note

not available in python bindings

bool QgsCoordinateTransform::datumTransformCrsInfo ( int  datumTransform, int &  epsgNr, QString &  srcProjection, QString &  dstProjection, QString &  remarks, QString &  scope, bool &  preferred, bool &  deprecated  )

static

Gets name of source and dest geographical CRS (to show in a tooltip)

Returns

epsgNr epsg code of the transformation (or 0 if not in epsg db)

QString QgsCoordinateTransform::datumTransformString ( int  datumTransform )

static

const QgsCoordinateReferenceSystem& QgsCoordinateTransform::destCRS ( ) const

inline

Get the QgsCoordinateReferenceSystem representation of the map canvas coordinate system

Returns

QgsCoordinateReferenceSystem of the map canvas coordinate system

int QgsCoordinateTransform::destinationDatumTransform ( ) const

inline

void QgsCoordinateTransform::initialise ( )

slot

initialise is used to actually create the Transformer instance

void QgsCoordinateTransform::invalidTransformInput ( ) const

signal

Signal when an invalid pj_transform() has occured.

bool QgsCoordinateTransform::isInitialised ( ) const

inline

Flag to indicate whether the coordinate systems have been initialised

Returns

true if initialised, otherwise false

bool QgsCoordinateTransform::isShortCircuited ( )

inline

See if the transform short circuits because src and dest are equivalent

Returns

bool True if it short circuits

bool QgsCoordinateTransform::readXML ( QDomNode &  theNode )

slot

Restores state from the given Dom node.

Parameters

theNode

The node from which state will be restored

Returns

bool True on success, False on failure

void QgsCoordinateTransform::setDestCRS

(

const QgsCoordinateReferenceSystem &

theCRS

)

Mutator for dest QgsCoordinateReferenceSystem

Parameters

theCRS

of the destination coordinate system

void QgsCoordinateTransform::setDestCRSID

(

long

theCRSID

)

Change the destination coordinate system by passing it a qgis srsid A QGIS srsid is a unique key value to an entry on the tbl_srs in the srs.db sqlite database.

Note

This slot will usually be called if the project properties change and a different coordinate system is selected.

This coord transform will be reinitialised when this slot is called to check if short circuiting is needed or not etc.

Parameters

theCRSID

- A long representing the srsid of the srs to be used

todo Add some logic here to determine if the srsid is a system or user one

void QgsCoordinateTransform::setDestinationDatumTransform ( int  dt )

inline

void QgsCoordinateTransform::setSourceCrs

(

const QgsCoordinateReferenceSystem &

theCRS

)

Set the source (layer) QgsCoordinateReferenceSystem

Parameters

theCRS

QgsCoordinateReferenceSystem representation of the layer's coordinate system

void QgsCoordinateTransform::setSourceDatumTransform ( int  dt )

inline

const QgsCoordinateReferenceSystem& QgsCoordinateTransform::sourceCrs ( ) const

inline

Get the QgsCoordinateReferenceSystem representation of the layer's coordinate system

Returns

QgsCoordinateReferenceSystem of the layer's coordinate system

int QgsCoordinateTransform::sourceDatumTransform ( ) const

inline

QgsPoint QgsCoordinateTransform::transform	(	const QgsPoint	p,
		TransformDirection	direction = ForwardTransform
	)		const

Transform the point from Source Coordinate System to Destination Coordinate System If the direction is ForwardTransform then coordinates are transformed from layer CS –> map canvas CS, otherwise points are transformed from map canvas CS to layerCS.

Parameters

p	Point to transform
direction	TransformDirection (defaults to ForwardTransform)

Returns

QgsPoint in Destination Coordinate System

QgsPoint QgsCoordinateTransform::transform	(	const double	x,
		const double	y = 0,
		TransformDirection	direction = ForwardTransform
	)		const

Transform the point specified by x,y from Source Coordinate System to Destination Coordinate System If the direction is ForwardTransform then coordinates are transformed from layer CS –> map canvas CS, otherwise points are transformed from map canvas CS to layerCS.

Parameters

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

Returns

QgsPoint in Destination Coordinate System

QgsRectangle QgsCoordinateTransform::transform	(	const QgsRectangle	theRect,
		TransformDirection	direction = ForwardTransform
	)		const

Transform a QgsRectangle to the dest Coordinate system If the direction is ForwardTransform then coordinates are transformed from layer CS –> map canvas CS, otherwise points are transformed from map canvas CS to layerCS.

Parameters

theRect	rect to transform
direction	TransformDirection (defaults to ForwardTransform)

Returns

QgsRectangle in Destination Coordinate System

QgsRectangle QgsCoordinateTransform::transformBoundingBox	(	const QgsRectangle	theRect,
		TransformDirection	direction = ForwardTransform,
		const bool	handle180Crossover = false
	)		const

Transform a QgsRectangle to the dest Coordinate system If the direction is ForwardTransform then coordinates are transformed from layer CS –> map canvas CS, otherwise points are transformed from map canvas CS to layerCS. It assumes that rect is a bounding box, and creates a bounding box in the proejcted CS, so that all points in source rectangle is within returned rectangle.

Parameters

theRect	rect to transform
direction	TransformDirection (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

QgsRectangle in Destination Coordinate System

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

Transform an array of coordinates to a different Coordinate System If the direction is ForwardTransform then coordinates are transformed from layer CS –> map canvas CS, otherwise points are transformed from map canvas CS to layerCS.

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	TransformDirection (defaults to ForwardTransform)

Returns

QgsRectangle in Destination Coordinate System

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

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

Note

not available in python bindings

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

bool QgsCoordinateTransform::writeXML ( QDomNode &  theNode, QDomDocument &  theDoc  )

slot

Stores state to the given Dom node in the given document

Parameters

theNode	The node in which state will be restored
theDoc	The document in which state will be stored

Returns

bool True on success, False on failure

---

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

• /tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgscoordinatetransform.h
• /tmp/buildd/qgis-2.6.0+wheezy1/src/core/qgscoordinatetransform.cpp