Class: QgsCurve

class qgis.core.QgsCurve

Bases: qgis._core.QgsAbstractGeometry

Constructor for QgsCurve.

QgsCurve(QgsCurve)

Abstract base class for curved geometry type

New in version 2.10: Enums

Methods

addToPainterPath

Adds a curve to a painter path.

adjacentVertices

asQPolygonF

Returns a QPolygonF representing the points.

boundary

boundingBox

calculateBoundingBox

childCount

childGeometry

childPoint

clearCache

clone

coordinateSequence

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.

hasChildGeometries

interpolatePoint

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

isClosed

Returns True if the curve is closed.

isRing

Returns True if the curve is a ring.

isValid

nextVertex

numPoints

Returns the number of points in the curve.

orientation

Returns the curve’s orientation, e.g.

partCount

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

segmentize

Returns a geometry without curves.

setZMTypeFromSubGeometry

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.

sumUpArea

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

toCurveType

vertexAt

vertexCount

vertexNumberFromVertexId

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.

Signals

Attributes

Clockwise

CounterClockwise

Clockwise = 0
CounterClockwise = 1
class Orientation

Bases: int

addToPainterPath(self, path: QPainterPath)

Adds a curve to a painter path.

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

Returns a QPolygonF representing the points.

boundary(self) → QgsAbstractGeometry
boundingBox(self) → QgsRectangle
calculateBoundingBox()
childCount(self) → int
childGeometry()
childPoint(self, index: int) → QgsPoint
clearCache(self)
clone(self) → QgsCurve
coordinateSequence(self) → 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.

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 – segmentation tolerance

  • toleranceType – 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)

drawAsPolygon(self, p: QPainter)

Draws the curve as a polygon on the specified QPainter.

Parameters

p – destination QPainter

endPoint(self) → QgsPoint

Returns the end point of the curve.

See also

startPoint()

equals(self, other: QgsCurve) → bool

Checks whether this curve exactly equals another curve.

New in version 3.0.

hasChildGeometries()
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.

isClosed(self) → bool

Returns True if the curve is closed.

isRing(self) → bool

Returns True if the curve is a ring.

isValid(self, flags: int = 0) → Tuple[bool, str]
nextVertex(self, id: QgsVertexId) → Tuple[bool, QgsPoint]
numPoints(self) → int

Returns the number of points in the curve.

orientation(self) → QgsCurve.Orientation

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.

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

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

Parameters
  • node – node number, where the first node is 0

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

Returns

  • True if node exists within the curve

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

points(self) → object

Returns a list of points within the curve.

reversed(self) → QgsCurve

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

New in version 2.14.

ringCount(self, part: int = 0) → 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 – segmentation tolerance

  • toleranceType – maximum segmentation angle or maximum difference between approximation and curve*

setZMTypeFromSubGeometry()
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.

startPoint(self) → QgsPoint

Returns the starting point of the curve.

See also

endPoint()

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.

sumUpArea(self) → float

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

toCurveType(self) → QgsCurve
vertexAt(self, id: QgsVertexId) → QgsPoint
vertexCount(self, part: int = 0, ring: int = 0) → int
vertexNumberFromVertexId(self, id: QgsVertexId) → int
xAt(self, index: int) → float

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

Parameters

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

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

Returns

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