Class: QgsSizeScaleTransformer

class qgis.core.QgsSizeScaleTransformer(type: QgsSizeScaleTransformer.ScaleType = QgsSizeScaleTransformer.Linear, minValue: float = 0, maxValue: float = 1, minSize: float = 0, maxSize: float = 1, nullSize: float = 0, exponent: float = 1)

Bases: qgis._core.QgsPropertyTransformer

Constructor for QgsSizeScaleTransformer.

Parameters:
  • type – scaling type
  • minValue – minimum expected value
  • maxValue – maximum expected value
  • minSize – minimum size to return
  • maxSize – maximum size to return
  • nullSize – size to return for null values
  • exponent – exponent for Exponential scaling method

QgsSizeScaleTransformer(QgsSizeScaleTransformer)

QgsPropertyTransformer subclass for scaling a value into a size according to various scaling methods.

New in version 3.0: Enums

Methods

clone
exponent Returns the exponent for an exponential expression.
fromExpression Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.
loadVariant
maxSize Returns the maximum calculated size.
minSize Returns the minimum calculated size.
nullSize Returns the size value when an expression evaluates to NULL.
setExponent Sets the exponent for an exponential expression.
setMaxSize Sets the maximum calculated size.
setMinSize Sets the minimum calculated size.
setNullSize Sets the size value for when an expression evaluates to NULL.
setType Sets the size transformer’s scaling type (the method used to calculate the size from a value).
size Calculates the size corresponding to a specific value.
toExpression
toVariant
transform
transformNumeric
transformerType
type Returns the size transformer’s scaling type (the method used to calculate the size from a value).

Signals

Attributes

Area
Exponential
Flannery
Linear
Area = 1
Exponential = 3
Flannery = 2
Linear = 0
class ScaleType

Bases: int

clone(self) → QgsSizeScaleTransformer
exponent(self) → float

Returns the exponent for an exponential expression.

See also

setExponent()

See also

type()

fromExpression(expression: str) → Tuple[QgsSizeScaleTransformer, str, str]

Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.

Parameters:
  • expression – expression to parse
  • 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 QgsSizeScaleTransformer, or None if expression could not
  • 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.

be parsed to a size scale transformer.

loadVariant(self, definition: Any) → bool
maxSize(self) → float

Returns the maximum calculated size.

See also

minSize()

minSize(self) → float

Returns the minimum calculated size.

See also

setMinSize()

See also

maxSize()

nullSize(self) → float

Returns the size value when an expression evaluates to NULL.

See also

setNullSize()

setExponent(self, exponent: float)

Sets the exponent for an exponential expression.

Parameters:exponent – exponent

See also

exponent()

setMaxSize(self, size: float)

Sets the maximum calculated size.

Parameters:size – maximum size

See also

maxSize()

See also

setMinSize()

setMinSize(self, size: float)

Sets the minimum calculated size.

Parameters:size – minimum size

See also

minSize()

See also

setMaxSize()

setNullSize(self, size: float)

Sets the size value for when an expression evaluates to NULL.

Parameters:size – null size

See also

nullSize()

setType(self, type: QgsSizeScaleTransformer.ScaleType)

Sets the size transformer’s scaling type (the method used to calculate the size from a value).

Parameters:type – scale type

See also

type()

size(self, value: float) → float

Calculates the size corresponding to a specific value.

Parameters:value – value to calculate size for
Returns:calculated size using size scale transformer’s parameters and type
toExpression(self, baseExpression: str) → str
toVariant(self) → Any
transform(self, context: QgsExpressionContext, value: Any) → Any
transformNumeric()
transformerType(self) → QgsPropertyTransformer.Type
type(self) → QgsSizeScaleTransformer.ScaleType

Returns the size transformer’s scaling type (the method used to calculate the size from a value).

See also

setType()