Class: QgsColorRampTransformer

class qgis.core.QgsColorRampTransformer

Bases: QgsPropertyTransformer

QgsPropertyTransformer subclass for transforming a numeric value into a color from a color ramp.

QgsColorRampTransformer(minValue: float = 0, maxValue: float = 1, ramp: QgsColorRamp = None, nullColor: Union[QColor, Qt.GlobalColor, QGradient] = QColor(0,0,0,0), rampName: str = ‘’) Constructor for QgsColorRampTransformer.

Parameters:
  • minValue – minimum expected value

  • maxValue – maximum expected value

  • ramp – source color ramp. Ownership is transferred to the transformer.

  • nullColor – color to return for null values

  • rampName – name of the source color ramp (since QGIS 3.36)

QgsColorRampTransformer(other: QgsColorRampTransformer) Copy constructor

Methods

clone

rtype:

QgsColorRampTransformer

color

Calculates the color corresponding to a specific value.

colorRamp

Returns the color ramp used for calculating property colors.

loadVariant

param definition:

nullColor

Returns the color corresponding to a null value.

rampName

Returns the color ramp's name.

setColorRamp

Sets the color ramp to use for calculating property colors.

setNullColor

Sets the color corresponding to a null value.

setRampName

Sets the color ramp's name.

toExpression

param baseExpression:

toVariant

rtype:

Any

transform

param context:

transformNumeric

Applies base class numeric transformations.

transformerType

rtype:

QgsPropertyTransformer.Type

clone(self) QgsColorRampTransformer
Return type:

QgsColorRampTransformer

color(self, value: float) QColor

Calculates the color corresponding to a specific value.

Parameters:

value (float) – value to calculate color for

Return type:

QColor

Returns:

calculated color using transformer’s parameters and type

colorRamp(self) QgsColorRamp

Returns the color ramp used for calculating property colors.

Return type:

QgsColorRamp

Returns:

color ramp

See also

setColorRamp()

loadVariant(self, definition: Any) bool
Parameters:

definition (Any) –

Return type:

bool

nullColor(self) QColor

Returns the color corresponding to a null value.

See also

setNullColor()

Return type:

QColor

rampName(self) str

Returns the color ramp’s name.

See also

setRampName()

Return type:

str

setColorRamp(self, ramp: QgsColorRamp)

Sets the color ramp to use for calculating property colors.

Parameters:

ramp (QgsColorRamp) – color ramp, ownership of ramp is transferred to the transformer.

See also

colorRamp()

setNullColor(self, color: QColor | Qt.GlobalColor | QGradient)

Sets the color corresponding to a null value.

Parameters:

color (Union[QColor) – null color

See also

nullColor()

setRampName(self, name: str)

Sets the color ramp’s name. The ramp name must be set to match a color ramp available in the style database for conversion to expression to work correctly.

See also

rampName()

Parameters:

name (str) –

toExpression(self, baseExpression: str) str
Parameters:

baseExpression (str) –

Return type:

str

toVariant(self) Any
Return type:

Any

transform(self, context: QgsExpressionContext, value: Any) Any
Parameters:
Return type:

Any

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.

transformerType(self) QgsPropertyTransformer.Type
Return type:

QgsPropertyTransformer.Type