Subgroup: Property
Class: QgsPropertyTransformer¶
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class
qgis.core.
QgsPropertyTransformer
¶ Bases:
sip.wrapper
Abstract base class for objects which transform the calculated value of a property. Possible uses include transformers which map a value into a scaled size or color from a gradient.
New in version 3.0: Methods
clone
Returns a clone of the transformer. create
Factory method for creating a new property transformer of the specified type. curveTransform
Returns the curve transform applied to input values before they are transformed by the individual transform subclasses. fromExpression
Attempts to parse an expression into a corresponding property transformer. loadVariant
Loads this transformer from a QVariantMap, wrapped in a QVariant. maxValue
Returns the maximum value expected by the transformer. minValue
Returns the minimum value expected by the transformer. setCurveTransform
Sets a curve transform to apply to input values before they are transformed by the individual transform subclasses. setMaxValue
Sets the maximum value expected by the transformer. setMinValue
Sets the minimum value expected by the transformer. toExpression
Converts the transformer to a QGIS expression string. toVariant
Saves this transformer to a QVariantMap, wrapped in a QVariant. transform
Calculates the transform of a value. transformNumeric
Applies base class numeric transformations. transformerType
Returns the transformer type. Attributes
ColorRampTransformer
GenericNumericTransformer
SizeScaleTransformer
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ColorRampTransformer
= 2¶
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GenericNumericTransformer
= 0¶
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SizeScaleTransformer
= 1¶
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class
Type
¶ Bases:
int
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clone
(self) → QgsPropertyTransformer¶ Returns a clone of the transformer.
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create
(type: QgsPropertyTransformer.Type) → QgsPropertyTransformer¶ Factory method for creating a new property transformer of the specified type.
Parameters: type – transformer type to create
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curveTransform
(self) → QgsCurveTransform¶ Returns the curve transform applied to input values before they are transformed by the individual transform subclasses.
See also
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fromExpression
(expression: str) → Tuple[QgsPropertyTransformer, str, str]¶ Attempts to parse an expression into a corresponding property transformer.
Parameters: - expression – expression to parse
- baseExpression – will be set to the component of the source expression which
is used to calculate the input to the property transformer. This will be set to an empty string if a field reference is the transformer input. :param fieldName: will be set to a field name which is used to calculate the input to the property transformer. This will be set to an empty string if an expression is the transformer input.
Returns: corresponding property transformer, or None if expression could not be parsed to a transformer.
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loadVariant
(self, transformer: Any) → bool¶ Loads this transformer from a QVariantMap, wrapped in a QVariant. You can use QgsXmlUtils.readVariant to read it from an XML document.
See also
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maxValue
(self) → float¶ Returns the maximum value expected by the transformer.
See also
See also
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minValue
(self) → float¶ Returns the minimum value expected by the transformer.
See also
See also
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setCurveTransform
(self, transform: QgsCurveTransform)¶ Sets a curve transform to apply to input values before they are transformed by the individual transform subclasses. Ownership of
transform
is transferred to the property transformer.See also
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setMaxValue
(self, max: float)¶ Sets the maximum value expected by the transformer.
Parameters: max – maximum value See also
See also
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setMinValue
(self, min: float)¶ Sets the minimum value expected by the transformer.
Parameters: min – minimum value See also
See also
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toExpression
(self, baseExpression: str) → str¶ Converts the transformer to a QGIS expression string. The
baseExpression
string consists of a sub-expression reflecting the parent property’s state.
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toVariant
(self) → Any¶ Saves this 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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transform
(self, context: QgsExpressionContext, value: Any) → Any¶ Calculates the transform of a value. Derived classes must implement this to perform their transformations on input values
Parameters: - context – expression context
- value – input value to transform
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transformNumeric
(self, input: float) → float¶ Applies base class numeric transformations. Derived classes should call this to transform an
input
numeric value before they apply any transform to the result. This applies any curve transforms which may exist on the transformer.
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transformerType
(self) → QgsPropertyTransformer.Type¶ Returns the transformer type.
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