Class: QgsNineCellFilter¶

Base class for raster analysis methods that work with a 3x3 cell filter and calculate the value of each cell based on the cell value and the eight neighbour cells.

Common examples are slope and aspect calculation in DEMs. Subclasses only implement the method that calculates the new value from the nine values. Everything else (reading file, writing file) is done by this subclass

Class Hierarchy¶

Subclasses¶

`QgsDerivativeFilter`	Adds the ability to calculate derivatives in x- and y-directions.
`QgsRuggednessFilter`	Calculates the ruggedness index based on a 3x3 moving window.
`QgsTotalCurvatureFilter`	Calculates total curvature as described by Wilson, Gallant (2000): terrain analysis.

Methods

`cellSizeX`
`cellSizeY`
`inputNodataValue`
`outputNodataValue`
`processNineCellWindow`	Calculates output value from nine input values.
`processRaster`	Starts the calculation, reads from mInputFile and stores the result in mOutputFile
`setCellSizeX`
`setCellSizeY`
`setInputNodataValue`
`setOutputNodataValue`
`setZFactor`
`zFactor`

class qgis.analysis.QgsNineCellFilter[source]¶

Bases: object

__init__(inputFile: str | None, outputFile: str | None, outputFormat: str | None)

Constructor that takes input file, output file and output format (GDAL string)

Parameters:

inputFile (Optional[str])
outputFile (Optional[str])
outputFormat (Optional[str])

__init__(a0: QgsNineCellFilter)

Parameters:: a0 (QgsNineCellFilter)

cellSizeX(self) → float[source]¶

Return type:: float

cellSizeY(self) → float[source]¶

Return type:: float

inputNodataValue(self) → float[source]¶

Return type:: float

outputNodataValue(self) → float[source]¶

Return type:: float

processNineCellWindow(self)[source]¶

Calculates output value from nine input values. The input values and the output value can be equal to the nodata value if not present or outside of the border. Must be implemented by subclasses.

First index of the input cell is the row, second index is the column

Parameters:

x11 – surrounding cell top left
x21 – surrounding cell central left
x31 – surrounding cell bottom left
x12 – surrounding cell top central
x22 – the central cell for which the value will be calculated
x32 – surrounding cell bottom central
x13 – surrounding cell top right
x23 – surrounding cell central right
x33 – surrounding cell bottom right

Returns:

the calculated cell value for the central cell x22

processRaster(self, feedback: QgsFeedback | None = None) → int[source]¶

Starts the calculation, reads from mInputFile and stores the result in mOutputFile

Parameters:: feedback (Optional[QgsFeedback] = None) – feedback object that receives update and that is checked for cancellation.
Return type:: int
Returns:: 0 in case of success

setCellSizeX(self, size: float)[source]¶

Parameters:: size (float)

setCellSizeY(self, size: float)[source]¶

Parameters:: size (float)

setInputNodataValue(self, value: float)[source]¶

Parameters:: value (float)

setOutputNodataValue(self, value: float)[source]¶

Parameters:: value (float)

setZFactor(self, factor: float)[source]¶

Parameters:: factor (float)

zFactor(self) → float[source]¶

Return type:: float