Subgroup: Curve
Class: QgsCurveTransform¶
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class
qgis.core.
QgsCurveTransform
¶ Bases:
sip.wrapper
Handles scaling of input values to output values by using a curve created from smoothly joining a number of set control points.
QgsCurveTransform assists in creation of curve type transforms, typically seen in raster image editing software (eg the curves dialog in GIMP or Photoshop). Transforms are created by passing a number of set control points through which the transform curve must pass. The curve is guaranteed to exactly pass through these control points. Between control points the curve is smoothly interpolated so that no disjoint sections or “corners” are present.
If the first or last control point are not located at x = 0 and x = 1 respectively, then values outside this range will be mapped to the y value of either the first or last control point. In other words, the curve will have a flat segment for values outside of the control point range.
New in version 3.0: Methods
addControlPoint
Adds a control point to the transform. controlPoints
Returns a list of the control points for the transform. loadVariant
Load this curve transformer from a QVariantMap, wrapped in a QVariant. readXml
Reads the curve’s state from an XML element. removeControlPoint
Removes a control point from the transform. setControlPoints
Sets the list of control points for the transform. toVariant
Saves this curve transformer to a QVariantMap, wrapped in a QVariant. writeXml
Writes the current state of the transform into an XML element y
Returns the mapped y value corresponding to the specified x
value.Attributes
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addControlPoint
(self, x: float, y: float)¶ Adds a control point to the transform. Behavior is undefined if duplicate x values exist in the control points list.
See also
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controlPoints
(self) → List[QgsPointXY]¶ Returns a list of the control points for the transform.
See also
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loadVariant
(self, transformer: Any) → bool¶ Load this curve transformer from a QVariantMap, wrapped in a QVariant. You can use QgsXmlUtils.writeVariant to load it from an XML document.
See also
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readXml
(self, elem: QDomElement, doc: QDomDocument) → bool¶ Reads the curve’s state from an XML element.
Parameters: - elem – source DOM element for transform’s state
- doc – DOM document
See also
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removeControlPoint
(self, x: float, y: float)¶ Removes a control point from the transform. This will have no effect if a matching control point does not exist.
See also
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setControlPoints
(self, points: Iterable[QgsPointXY])¶ Sets the list of control points for the transform. Any existing points are removed.
See also
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toVariant
(self) → Any¶ Saves this curve transformer to a QVariantMap, wrapped in a QVariant. You can use QgsXmlUtils.writeVariant to save it to an XML document.
See also
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writeXml
(self, transformElem: QDomElement, doc: QDomDocument) → bool¶ Writes the current state of the transform into an XML element
Parameters: - transformElem – destination element for the transform’s state
- doc – DOM document
See also
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y
(self, x: float) → float¶ Returns the mapped y value corresponding to the specified
x
value.y(self, x: Iterable[float]) -> List[float] Returns a list of y values corresponding to a list of
x
values. Calling this method is faster then calling the double variant multiple times.
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