Class: QgsContrastEnhancement

class qgis.core.QgsContrastEnhancement

Bases: sip.wrapper

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

Methods

contrastEnhancementAlgorithm

rtype

QgsContrastEnhancement.ContrastEnhancementAlgorithm

contrastEnhancementAlgorithmFromString

Deserialize ContrastEnhancementAlgorithm.

contrastEnhancementAlgorithmString

Returns a string to serialize 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.

maximumValue

Returns the maximum value for the contrast enhancement range.

maximumValuePossible

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

minimumValue

Returns the minimum value for the contrast enhancement range.

minimumValuePossible

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

readXml

param elem

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

param doc

Attributes

ClipToMinimumMaximum

NoEnhancement

StretchAndClipToMinimumMaximum

StretchToMinimumMaximum

UserDefinedEnhancement

ClipToMinimumMaximum = 3
class ContrastEnhancementAlgorithm

Bases: int

NoEnhancement = 0
StretchAndClipToMinimumMaximum = 2
StretchToMinimumMaximum = 1
UserDefinedEnhancement = 4
contrastEnhancementAlgorithm(self)QgsContrastEnhancement.ContrastEnhancementAlgorithm
Return type

QgsContrastEnhancement.ContrastEnhancementAlgorithm

contrastEnhancementAlgorithmFromString(contrastEnhancementString: str)QgsContrastEnhancement.ContrastEnhancementAlgorithm

Deserialize ContrastEnhancementAlgorithm.

Parameters

contrastEnhancementString (str) –

Return type

QgsContrastEnhancement.ContrastEnhancementAlgorithm

contrastEnhancementAlgorithmString(algorithm: QgsContrastEnhancement.ContrastEnhancementAlgorithm) → str

Returns a string to serialize ContrastEnhancementAlgorithm.

Parameters

algorithm (QgsContrastEnhancement.ContrastEnhancementAlgorithm) –

Return type

str

enhanceContrast(self, value: float) → int

Applies the contrast enhancement to a value. Return values are 0 - 254, -1 means the pixel was clipped and should not be displayed.

Parameters

value (float) –

Return type

int

isValueInDisplayableRange(self, value: float) → bool

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

Returns the maximum value for the contrast enhancement range.

Return type

float

maximumValuePossible(dataType: Qgis.DataType) → float

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

Parameters

dataType (Qgis.DataType) –

Return type

float

minimumValue(self) → float

Returns the minimum value for the contrast enhancement range.

Return type

float

minimumValuePossible(dataType: Qgis.DataType) → float

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

Parameters

dataType (Qgis.DataType) –

Return type

float

readXml(self, elem: QDomElement)
Parameters

elem (QDomElement) –

setContrastEnhancementAlgorithm(self, algorithm: QgsContrastEnhancement.ContrastEnhancementAlgorithm, generateTable: bool = True)

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
setContrastEnhancementFunction(self, function: QgsContrastEnhancementFunction)

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

Parameters

function (QgsContrastEnhancementFunction) –

setMaximumValue(self, value: float, generateTable: bool = True)

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.

Parameters
  • value (float) –

  • generateTable (bool = True) –

setMinimumValue(self, value: float, generateTable: bool = True)

Sets the minimum 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 maximum value or the contrast enhancement algorithm, you can elect to not generate the lookup table. By default it will be generated.

Parameters
  • value (float) –

  • generateTable (bool = True) –

toSld(self, doc: QDomDocument, element: QDomElement)

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

New in version 3.6.

Parameters
  • doc (QDomDocument) –

  • element (QDomElement) –

writeXml(self, doc: QDomDocument, parentElem: QDomElement)
Parameters
  • doc (QDomDocument) –

  • parentElem (QDomElement) –