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[processing] added native raster calculator algorithm
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volaya committed Dec 1, 2016
1 parent fcc3437 commit a7f9018e11be823c090999434667268fee39fe03
@@ -552,3 +552,18 @@ qgis:voronoipolygons: >


qgis:rastercalculator: >
This algorithm allows to perform algebraic operations using raster layers.

The resulting layer will have its values computed according to an expression. The expression can contain numerical values, operators and references to any of the layers in the current project. The following functions are also supported:

- sin(), cos(), tan(), atan2(), ln(), log10()

The extent and cellsize can be defined by the user. If the extent is not specified, the minimum extent that covers the input layers will be used. If the cellsize is not specified, the minimum cellsize of all input layers will be used.

The cellsize is assumed to be the same in both X and Y axes.

Layers are refered by their name as displayed in the layer list and the number of the band to use (based on 1), using the pattern 'layer_name@band number'. For instance, the first band from a layer named DEM will be referred as DEM@1.

When using the calculator in the batch interface or from the console, the files to use have to be specified. The corresponding layers are refered using the base name of the file (without the full path). For instance, is using a layer at path/to/my/rasterfile.tif, the first band of that layer will be refered as rasterfile.tif@1.

@@ -178,6 +178,7 @@
from .GeometryByExpression import GeometryByExpression
from .SnapGeometries import SnapGeometriesToLayer
from .PoleOfInaccessibility import PoleOfInaccessibility
from .RasterCalculator import RasterCalculator
from .CreateAttributeIndex import CreateAttributeIndex
from .DropGeometry import DropGeometry
from .BasicStatistics import BasicStatisticsForField
@@ -245,7 +246,7 @@ def __init__(self):
RemoveNullGeometry(), ExtractByExpression(), ExtendLines(),
ExtractSpecificNodes(), GeometryByExpression(), SnapGeometriesToLayer(),
PoleOfInaccessibility(), CreateAttributeIndex(), DropGeometry(),
BasicStatisticsForField(), RasterCalculator()

if hasMatplotlib:
@@ -0,0 +1,164 @@
# -*- coding: utf-8 -*-

Date : November 2016
Copyright : (C) 2016 by Victor Olaya
Email : volayaf at gmail dot com
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
from processing.modeler.ModelerAlgorithm import ValueFromInput, ValueFromOutput
import os

__author__ = 'Victor Olaya'
__date__ = 'November 2016'
__copyright__ = '(C) 2016, Victor Olaya'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

import math
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.parameters import ParameterMultipleInput, ParameterExtent, ParameterString, ParameterRaster, ParameterNumber
from processing.core.outputs import OutputRaster
from import dataobjects
from processing.algs.gdal.GdalUtils import GdalUtils
from qgis.core import QgsRectangle
from qgis.analysis import QgsRasterCalculator, QgsRasterCalculatorEntry
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.algs.qgis.ui.RasterCalculatorWidgets import LayersListWidgetWrapper, ExpressionWidgetWrapper

class RasterCalculator(GeoAlgorithm):


def defineCharacteristics(self):, self.i18n_name = self.trAlgorithm('Raster calculator'), self.i18n_group = self.trAlgorithm('Raster')

self.addParameter(ParameterMultipleInput(self.LAYERS,'Input layers'),
metadata = {'widget_wrapper': LayersListWidgetWrapper}))
class ParameterExpression(ParameterString):
def evaluateForModeler(self, value, model):
#print value
for i in list(model.inputs.values()):
param = i.param
if isinstance(param, ParameterRaster):
new = "%s@" % os.path.basename(param.value)
old = "%s@" %
value = value.replace(old, new)

for alg in list(model.algs.values()):
for out in alg.algorithm.outputs:
print out, out.value
if isinstance(out, OutputRaster):
if out.value:
new = "%s@" % os.path.basename(out.value)
old = "%s:%s@" % (,
value = value.replace(old, new)
return value

metadata = {'widget_wrapper': ExpressionWidgetWrapper}))
self.addParameter(ParameterNumber(self.CELLSIZE,'Cellsize (use 0 or empty to set it automatically)'),
minValue=0.0, default=0.0, optional=True))
self.addParameter(ParameterExtent(self.EXTENT,'Output extent'),

def processAlgorithm(self, progress):
expression = self.getParameterValue(self.EXPRESSION)
layersValue = self.getParameterValue(self.LAYERS)
layersDict = {}
if layersValue:
layers = [dataobjects.getObjectFromUri(f) for f in layersValue.split(";")]
layersDict = {os.path.basename(lyr.source()): lyr for lyr in layers}

for lyr in dataobjects.getRasterLayers():
name =
if (name + "@") in expression:
layersDict[name] = lyr

entries = []
for name, lyr in layersDict.iteritems():
for n in xrange(lyr.bandCount()):
entry = QgsRasterCalculatorEntry()
entry.ref = '%s@%i' % (name, n + 1)
entry.raster = lyr
entry.bandNumber = n + 1

output = self.getOutputValue(self.OUTPUT)
extentValue = self.getParameterValue(self.EXTENT)

if extentValue:
extent = extentValue.split(',')
bbox = QgsRectangle(float(extent[0]), float(extent[2]),
float(extent[1]), float(extent[3]))
if layersDict:
bbox = layersDict.values()[0].extent()
for lyr in layersDict.values():
raise GeoAlgorithmExecutionException("No layers selected"))
def _cellsize(layer):
return (layer.extent().xMaximum() - layer.extent().xMinimum()) / layer.width()
cellsize = self.getParameterValue(self.CELLSIZE) or min([_cellsize(lyr) for lyr in layersDict.values()])
width = math.floor((bbox.xMaximum() - bbox.xMinimum()) / cellsize)
height = math.floor((bbox.yMaximum() - bbox.yMinimum()) / cellsize)
driverName = GdalUtils.getFormatShortNameFromFilename(output)
calc = QgsRasterCalculator(expression,

res = calc.processCalculation()
if res == QgsRasterCalculator.ParserError:
raise GeoAlgorithmExecutionException("Error parsing formula"))

def processBeforeAddingToModeler(self, algorithm, model):
values = []
expression = algorithm.params[self.EXPRESSION]
for i in list(model.inputs.values()):
param = i.param
if isinstance(param, ParameterRaster) and "%s@" % in expression:

dependent = model.getDependentAlgorithms(
dependent = []
for alg in list(model.algs.values()):
if not in dependent:
for out in alg.algorithm.outputs:
if (isinstance(out, OutputRaster)
and "%s:%s@" % (, in expression):

algorithm.params[self.LAYERS] = values

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