Class: QgsNineCellFilter

class qgis.analysis.QgsNineCellFilter

Bases: sip.wrapper

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

QgsNineCellFilter(inputFile: str, outputFile: str, outputFormat: str) Constructor that takes input file, output file and output format (GDAL string)

QgsNineCellFilter(QgsNineCellFilter)

Methods

cellSizeX

rtype

float

cellSizeY

rtype

float

inputNodataValue

rtype

float

outputNodataValue

rtype

float

processNineCellWindow

Calculates output value from nine input values.

processRaster

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

setCellSizeX

param size

setCellSizeY

param size

setInputNodataValue

param value

setOutputNodataValue

param value

setZFactor

param factor

zFactor

rtype

float

cellSizeX(self)float
Return type

float

cellSizeY(self)float
Return type

float

inputNodataValue(self)float
Return type

float

outputNodataValue(self)float
Return type

float

processNineCellWindow(self)Tuple[float, float, float, float, float, float, float, float, float, float]

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

Return type

Tuple[float, float, float, float, float, float, float, float, float, float]

Returns

the calculated cell value for the central cell x22

processRaster(self, feedback: QgsFeedback = None)int

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

Parameters

feedback (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)
Parameters

size (float) –

setCellSizeY(self, size: float)
Parameters

size (float) –

setInputNodataValue(self, value: float)
Parameters

value (float) –

setOutputNodataValue(self, value: float)
Parameters

value (float) –

setZFactor(self, factor: float)
Parameters

factor (float) –

zFactor(self)float
Return type

float