Class: QgsContrastEnhancement¶

Handles contrast enhancement and clipping.

Manipulates raster or point cloud pixel values so that they enhance contrast or clip into a specified numerical range according to the specified ContrastEnhancementAlgorithm.

Methods

`contrastEnhancementAlgorithm`
`enhanceContrast`	Applies the contrast enhancement to a value.
`isValueInDisplayableRange`	Returns `True` if a pixel value is in displayable range, `False` if pixel is outside of range (i.e. clipped).
`maximumValue`	Returns the maximum value for the contrast enhancement range.
`minimumValue`	Returns the minimum value for the contrast enhancement range.
`readXml`
`setContrastEnhancementAlgorithm`	Sets the contrast enhancement algorithm.
`setContrastEnhancementFunction`	Allows the user to set their own custom contrast enhancement function.
`setMaximumValue`	Sets the maximum value for the contrast enhancement range.
`setMinimumValue`	Sets the minimum value for the contrast enhancement range.
`toSld`	Write ContrastEnhancement tags following SLD v1.0 specs SLD1.0 is limited to the parameters listed in: https://docs.geoserver.org/stable/en/user/styling/sld/reference/rastersymbolizer.html#contrastenhancement Btw only sld:Normalize + vendor options are supported because there is no clear mapping of ContrastEnhancement parameters to support sld:Histogram or sld:GammaValue
`writeXml`

Static Methods

`contrastEnhancementAlgorithmFromString`	Deserialize ContrastEnhancementAlgorithm.
`contrastEnhancementAlgorithmString`	Returns a string to serialize ContrastEnhancementAlgorithm.
`maximumValuePossible`	Helper function that returns the maximum possible value for a data type.
`minimumValuePossible`	Helper function that returns the minimum possible value for a data type.

Attributes

`ClipToMinimumMaximum`
`NoEnhancement`
`StretchAndClipToMinimumMaximum`
`StretchToMinimumMaximum`
`UserDefinedEnhancement`

class qgis.core.QgsContrastEnhancement[source]¶

Bases: object

__init__(datatype: Qgis.DataType = Qgis.DataType.Byte)

Constructor for QgsContrastEnhancement, for the specified data type.

Parameters:: datatype (Qgis.DataType = Qgis.DataType.Byte)

__init__(ce: QgsContrastEnhancement)

Parameters:: ce (QgsContrastEnhancement)

ClipToMinimumMaximum = 3¶

class ContrastEnhancementAlgorithm¶: Bases: int

NoEnhancement = 0¶

StretchAndClipToMinimumMaximum = 2¶

StretchToMinimumMaximum = 1¶

UserDefinedEnhancement = 4¶

contrastEnhancementAlgorithm(self) → QgsContrastEnhancement.ContrastEnhancementAlgorithm[source]¶

Return type:: QgsContrastEnhancement.ContrastEnhancementAlgorithm

static contrastEnhancementAlgorithmFromString(contrastEnhancementString: str | None) → QgsContrastEnhancement.ContrastEnhancementAlgorithm[source]¶

Deserialize ContrastEnhancementAlgorithm.

Parameters:: contrastEnhancementString (Optional[str])
Return type:: QgsContrastEnhancement.ContrastEnhancementAlgorithm

static contrastEnhancementAlgorithmString(algorithm: QgsContrastEnhancement.ContrastEnhancementAlgorithm) → str[source]¶

Returns a string to serialize ContrastEnhancementAlgorithm.

Parameters:: algorithm (QgsContrastEnhancement.ContrastEnhancementAlgorithm)
Return type:: str

enhanceContrast(self, value: float) → int[source]¶

Applies the contrast enhancement to a value. Return values are 0 - 255, -1 means the pixel was clipped and should not be displayed.

Parameters:: value (float)
Return type:: int

isValueInDisplayableRange(self, value: float) → bool[source]¶

Returns True if a pixel value is in displayable range, False if pixel is outside of range (i.e. clipped).

Parameters:: value (float)
Return type:: bool

maximumValue(self) → float[source]¶

Returns the maximum value for the contrast enhancement range.

Return type:: float

static maximumValuePossible(dataType: Qgis.DataType) → float[source]¶

Helper function that returns the maximum possible value for a data type.

Parameters:: dataType (Qgis.DataType)
Return type:: float

minimumValue(self) → float[source]¶

Returns the minimum value for the contrast enhancement range.

Return type:: float

static minimumValuePossible(dataType: Qgis.DataType) → float[source]¶

Helper function that returns the minimum possible value for a data type.

Parameters:: dataType (Qgis.DataType)
Return type:: float

readXml(self, elem: QDomElement)[source]¶

Parameters:: elem (QDomElement)

setContrastEnhancementAlgorithm(self, algorithm: QgsContrastEnhancement.ContrastEnhancementAlgorithm, generateTable: bool = True)[source]¶

Sets the contrast enhancement algorithm.

The generateTable parameter is optional and is for performance improvements. If you know you are immediately going to set the Minimum or Maximum value, you can elect to not generate the lookup tale. By default it will be generated.

Parameters:

algorithm (QgsContrastEnhancement.ContrastEnhancementAlgorithm)
generateTable (bool = True)

setContrastEnhancementFunction(self, function: QgsContrastEnhancementFunction | None)[source]¶

Allows the user to set their own custom contrast enhancement function. Ownership of function is transferred.

Parameters:: function (Optional[QgsContrastEnhancementFunction])

setMaximumValue(self, value: float, generateTable: bool = True)[source]¶

Sets the maximum value for the contrast enhancement range.

The generateTable parameter is optional and is for performance improvements. If you know you are immediately going to set the minimum value or the contrast enhancement algorithm, you can elect to not generate the lookup table. By default it will be generated.