Class: QgsCurve

class qgis.core.QgsCurve

Bases: QgsAbstractGeometry

Abstract base class for curved geometry type

New in version 2.10.

QgsCurve() Constructor for QgsCurve.

QgsCurve(QgsCurve)

Enums

Orientation

alias of AngularDirection

Methods

addToPainterPath	Adds a curve to a painter path.
adjacentVertices	param vertex:
asKml	param precision:
asQPainterPath	rtype: QPainterPath
asQPolygonF	Returns a QPolygonF representing the points.
boundary	rtype: QgsAbstractGeometry
boundingBox	rtype: QgsRectangle
clone	rtype: QgsCurve
coordinateSequence	rtype: object
curveSubstring	Returns a new curve representing a substring of this curve.
curveToLine	Returns a new line string geometry corresponding to a segmentized approximation of the curve.
drawAsPolygon	Draws the curve as a polygon on the specified QPainter.
endPoint	Returns the end point of the curve.
equals	Checks whether this curve exactly equals another curve.
indexOf	Returns the index of the first vertex matching the given point, or -1 if a matching vertex is not found.
interpolatePoint	Returns an interpolated point on the curve at the specified distance.
isClosed	Returns True if the curve is closed.
isClosed2D	Returns true if the curve is closed.
isRing	Returns True if the curve is a ring.
isValid	param flags:
nextVertex	param id:
normalize
numPoints	Returns the number of points in the curve.
orientation	Returns the curve's orientation, e.g.
partCount	rtype: int
pointAt	Returns the point and vertex id of a point within the curve.
points	Returns a list of points within the curve.
reversed	Returns a reversed copy of the curve, where the direction of the curve has been flipped.
ringCount	param part:
scroll	Scrolls the curve vertices so that they start with the vertex at the given index.
segmentize	Returns a geometry without curves.
sinuosity	Returns the curve sinuosity, which is the ratio of the curve length() to curve straightDistance2d().
startPoint	Returns the starting point of the curve.
straightDistance2d	Returns the straight distance of the curve, i.e. the direct/euclidean distance between the first and last vertex of the curve.
sumUpArea	Sums up the area of the curve by iterating over the vertices (shoelace formula).
toCurveType	rtype: QgsCurve
vertexAt	param id:
vertexCount	param part:
vertexNumberFromVertexId	param id:
xAt	Returns the x-coordinate of the specified node in the line string.
yAt	Returns the y-coordinate of the specified node in the line string.

Orientation

alias of AngularDirection

addToPainterPath(self, path: QPainterPath)

Adds a curve to a painter path.

Parameters:

path (QPainterPath) –

adjacentVertices(self, vertex: QgsVertexId) → Tuple[QgsVertexId, QgsVertexId]

Parameters:

vertex (QgsVertexId) –

Return type:

Tuple[QgsVertexId, QgsVertexId]

asKml(self, precision: int = 17) → str

Parameters:

precision (int = 17) –

Return type:

str

asQPainterPath(self) → QPainterPath

Return type:

QPainterPath

asQPolygonF(self) → QPolygonF

Returns a QPolygonF representing the points.

Return type:

QPolygonF

boundary(self) → QgsAbstractGeometry

Return type:

QgsAbstractGeometry

boundingBox(self) → QgsRectangle

Return type:

QgsRectangle

clone(self) → QgsCurve

Return type:

QgsCurve

coordinateSequence(self) → object

Return type:

object

curveSubstring(self, startDistance: float, endDistance: float) → QgsCurve

Returns a new curve representing a substring of this curve.

The startDistance and endDistance arguments specify the length along the curve which the substring should start and end at. If the endDistance is greater than the total length of the curve then any “extra” length will be ignored.

If z or m values are present, the output z and m will be interpolated using the existing vertices’ z or m values.

New in version 3.4.

Parameters:

• startDistance (float) –

• endDistance (float) –

Return type:

QgsCurve

curveToLine(self, tolerance: float = M_PI_2 / 90, toleranceType: QgsAbstractGeometry.SegmentationToleranceType = QgsAbstractGeometry.MaximumAngle) → QgsLineString

Returns a new line string geometry corresponding to a segmentized approximation of the curve.

Parameters:

• tolerance (float = M_PI_2/90) – segmentation tolerance

• toleranceType (QgsAbstractGeometry.SegmentationToleranceType = QgsAbstractGeometry.MaximumAngle) – maximum segmentation angle or maximum difference between approximation and curve

Uses a MaximumAngle tolerance of 1 degrees by default (360 segments in a full circle)

Return type:

QgsLineString

drawAsPolygon(self, p: QPainter)

Draws the curve as a polygon on the specified QPainter.

Parameters:

p (QPainter) – destination QPainter

endPoint(self) → QgsPoint

Returns the end point of the curve.

See also

startPoint()

Return type:

QgsPoint

equals(self, other: QgsCurve) → bool

Checks whether this curve exactly equals another curve.

New in version 3.0.

Parameters:

other (QgsCurve) –

Return type:

bool

indexOf(self, point: QgsPoint) → int

Returns the index of the first vertex matching the given point, or -1 if a matching vertex is not found.

Note

If the curve has m or z values then the search point must have exactly matching m and z values in order to be matched against the curve’s vertices.

Note

This method only matches against segment vertices, not curve vertices.

New in version 3.20.

Parameters:

point (QgsPoint) –

Return type:

int

interpolatePoint(self, distance: float) → QgsPoint

Returns an interpolated point on the curve at the specified distance.

If z or m values are present, the output z and m will be interpolated using the existing vertices’ z or m values.

If distance is negative, or is greater than the length of the curve, None will be returned.

New in version 3.4.

Parameters:

distance (float) –

Return type:

QgsPoint

isClosed(self) → bool

Returns True if the curve is closed.

See also

isClosed2D()

Return type:

bool

isClosed2D(self) → bool

Returns true if the curve is closed.

Unlike isClosed. It looks only for XY coordinates.

See also

isClosed()

New in version 3.20.

Return type:

bool

isRing(self) → bool

Returns True if the curve is a ring.

Return type:

bool

isValid(self, flags: Qgis.GeometryValidityFlags | Qgis.GeometryValidityFlag = Qgis.GeometryValidityFlags()) → Tuple[bool, str]

Parameters:

flags (Union[Qgis.GeometryValidityFlags) –

Return type:

Tuple[bool, str]

nextVertex(self, id: QgsVertexId) → Tuple[bool, QgsPoint]

Parameters:

id (QgsVertexId) –

Return type:

Tuple[bool, QgsPoint]

normalize(self)

numPoints(self) → int

Returns the number of points in the curve.

Return type:

int

orientation(self) → Qgis.AngularDirection

Returns the curve’s orientation, e.g. clockwise or counter-clockwise.

Warning

The result is not predictable for non-closed curves.

New in version 3.6.

Return type:

Qgis.AngularDirection

partCount(self) → int

Return type:

int

pointAt(self, node: int) → Tuple[bool, QgsPoint, Qgis.VertexType]

Returns the point and vertex id of a point within the curve.

Parameters:

node (int) – node number, where the first node is 0

Return type:

Tuple[bool, QgsPoint, Qgis.VertexType]

Returns:

• True if node exists within the curve

• point: will be set to point at corresponding node in the curve

• type: will be set to the vertex type of the node

points(self) → List[QgsPoint]

Returns a list of points within the curve.

Return type:

List[QgsPoint]

reversed(self) → QgsCurve

Returns a reversed copy of the curve, where the direction of the curve has been flipped.

New in version 2.14.

Return type:

QgsCurve

ringCount(self, part: int = 0) → int

Parameters:

part (int = 0) –

Return type:

int

scroll(self, firstVertexIndex: int)

Scrolls the curve vertices so that they start with the vertex at the given index.

Warning

This should only be called on closed curves, or the shape of the curve will be altered and the result is undefined.

Warning

The firstVertexIndex must correspond to a segment vertex and not a curve point or the result is undefined.

New in version 3.20.

Parameters:

firstVertexIndex (int) –

segmentize(self, tolerance: float = M_PI_2 / 90, toleranceType: QgsAbstractGeometry.SegmentationToleranceType = QgsAbstractGeometry.MaximumAngle) → QgsCurve

Returns a geometry without curves. Caller takes ownership

Parameters:

• tolerance (float = M_PI_2/90) – segmentation tolerance

• toleranceType (QgsAbstractGeometry.SegmentationToleranceType = QgsAbstractGeometry.MaximumAngle) – maximum segmentation angle or maximum difference between approximation and curve

Return type:

QgsCurve

sinuosity(self) → float

Returns the curve sinuosity, which is the ratio of the curve length() to curve straightDistance2d(). Larger numbers indicate a more “sinuous” curve (i.e. more “bendy”). The minimum value returned of 1.0 indicates a perfectly straight curve.

If a curve isClosed(), it has infinite sinuosity and will return NaN.

New in version 3.2.

Return type:

float

startPoint(self) → QgsPoint

Returns the starting point of the curve.

See also

endPoint()

Return type:

QgsPoint

straightDistance2d(self) → float

Returns the straight distance of the curve, i.e. the direct/euclidean distance between the first and last vertex of the curve. (Also known as “as the crow flies” distance).

New in version 3.2.

Return type:

float

sumUpArea(self) → float

Sums up the area of the curve by iterating over the vertices (shoelace formula).

Return type:

float

toCurveType(self) → QgsCurve

Return type:

QgsCurve

vertexAt(self, id: QgsVertexId) → QgsPoint

Parameters:

id (QgsVertexId) –

Return type:

QgsPoint

vertexCount(self, part: int = 0, ring: int = 0) → int

Parameters:

• part (int = 0) –

• ring (int = 0) –

Return type:

int

vertexNumberFromVertexId(self, id: QgsVertexId) → int

Parameters:

id (QgsVertexId) –

Return type:

int

xAt(self, index: int) → float

Returns the x-coordinate of the specified node in the line string.

Parameters:

index (int) – index of node, where the first node in the line is 0

Return type:

float

Returns:

x-coordinate of node, or 0.0 if index is out of bounds

yAt(self, index: int) → float

Returns the y-coordinate of the specified node in the line string.

Parameters:

index (int) – index of node, where the first node in the line is 0

Return type:

float

Returns:

y-coordinate of node, or 0.0 if index is out of bounds