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change expression to use layers in the current execution scope

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luipir committed Jul 10, 2018
1 parent 5ebe5d6 commit 5a3b319e1c14bd4a428cb4e8003b439e7b127b2c
Showing with 90 additions and 12 deletions.
  1. +90 −12 python/plugins/processing/algs/qgis/RasterCalculator.py
@@ -40,7 +40,8 @@
QgsProcessingParameterRasterLayer,
QgsProcessingOutputRasterLayer,
QgsProcessingParameterString,
QgsCoordinateTransform)
QgsCoordinateTransform,
QgsMapLayer)
from qgis.analysis import QgsRasterCalculator, QgsRasterCalculatorEntry


@@ -77,6 +78,7 @@ def type(self):
def clone(self):
return ParameterRasterCalculatorExpression(self.name(), self.description(), self.multiLine())

# TODO: remove this unused method?
def evaluateForModeler(self, value, model):
for i in list(model.inputs.values()):
param = i.param
@@ -125,15 +127,16 @@ def processAlgorithm(self, parameters, context, feedback):
layersDict = {os.path.basename(lyr.source().split(".")[0]): lyr for lyr in layers}

crs = self.parameterAsCrs(parameters, self.CRS, context)
if not layers and not crs.isValid():
raise QgsProcessingException(self.tr("No reference layer selected nor CRS provided"))

if not crs.isValid() and layers:
crs = list(layersDict.values())[0].crs()
if not crs or not crs.isValid():
if not layers:
raise QgsProcessingException(self.tr("No reference layer selected nor CRS provided"))
else:
crs = list(layersDict.values())[0].crs()

bbox = self.parameterAsExtent(parameters, self.EXTENT, context)
if not layers and bbox.isNull():
raise QgsProcessingException(self.tr("No reference layer selected nor extent box provided"))
if not bbox or bbox.isNull():
if not layers:
raise QgsProcessingException(self.tr("No reference layer selected nor extent box provided"))

if not bbox.isNull():
bboxCrs = self.parameterAsExtentCrs(parameters, self.EXTENT, context)
@@ -145,7 +148,7 @@ def processAlgorithm(self, parameters, context, feedback):
bbox = QgsProcessingUtils.combineLayerExtents(layers, crs)

cellsize = self.parameterAsDouble(parameters, self.CELLSIZE, context)
if not layers and cellsize == 0:
if cellsize == 0 and not layers:
raise QgsProcessingException(self.tr("No reference layer selected nor cellsize value provided"))

def _cellsize(layer):
@@ -157,15 +160,23 @@ def _cellsize(layer):
if cellsize == 0:
cellsize = min([_cellsize(lyr) for lyr in layersDict.values()])

# check for layers available in the model
layersDictCopy = layersDict.copy() # need a shallow copy because next calls invalidate iterator
for lyr in layersDictCopy.values():
expression = self.mappedNameToLayer(lyr, expression, layersDict, context)

# check for layers available in the project
for lyr in QgsProcessingUtils.compatibleRasterLayers(context.project()):
name = lyr.name()
if (name + "@") in expression:
layersDict[name] = lyr
expression = self.mappedNameToLayer(lyr, expression, layersDict, context)

# create the list of layers to be passed as inputs to RasterCalculaltor
# at this phase expression has been modified to match available layers
# in the current scope
entries = []
for name, lyr in layersDict.items():
for n in range(lyr.bandCount()):
ref = '{:s}@{:d}'.format(name, n + 1)

if ref in expression:
entry = QgsRasterCalculatorEntry()
entry.ref = ref
@@ -178,6 +189,7 @@ def _cellsize(layer):
width = math.floor((bbox.xMaximum() - bbox.xMinimum()) / cellsize)
height = math.floor((bbox.yMaximum() - bbox.yMinimum()) / cellsize)
driverName = GdalUtils.getFormatShortNameFromFilename(output)

calc = QgsRasterCalculator(expression,
output,
driverName,
@@ -213,3 +225,69 @@ def processBeforeAddingToModeler(self, algorithm, model):
values.append(ValueFromOutput(alg.modeler_name, out.name))

algorithm.params[self.LAYERS] = values

def mappedNameToLayer(self, lyr, expression, layersDict, context):
'''Try to identify if a real layer is mapped in the expression with a symbolic name.'''

nameToMap = lyr.name()

# get last scope of the expressionContext because should be that related
# with mapped variables
# The scope name should be "algorithm_inputs"
expContextLastScope = context.expressionContext().lastScope()

# check for layers directly added in the expression
if (nameToMap + "@") in expression:
layersDict[nameToMap] = lyr

# check for the layers that are mapped as input in a model
# to do this check in the latest scope all passed variables
# to look for a variable that is a layer or a string filename ç
# to a layer
varId = None
varDescription = None

for varName in expContextLastScope.variableNames():

layer = expContextLastScope.variable(varName)

if not isinstance(layer, str) and not isinstance(layer, QgsMapLayer):
continue

if isinstance(layer, QgsMapLayer) and nameToMap not in layer.source():
continue

varId = varName
varDescription = expContextLastScope.description(varName)

# because there can be variable with None or "" description
# then skip them
if not varDescription:
continue

# check if it's description starts with Output as in:
# Output 'Output' from algorithm 'calc1'
# as set in https://github.com/qgis/QGIS/blob/master/src/core/processing/models/qgsprocessingmodelalgorithm.cpp#L516
# but var in expression is called simply
# 'Output' from algorithm 'calc1'
elements = varDescription.split(" ")
if len(elements) > 1 and elements[0] == "Output":
# remove heading "Output " string
varDescription = varDescription[7:]

# check if cleaned varDescription is present in the expression
# if not skip it
if (varDescription + "@") not in expression:
continue

# !!!found!!! => substitute in expression
# and add in the list of layers that will be passed to raster calculator
nameToMap = varName
new = "{}@".format(nameToMap)
old = "{}@".format(varDescription)
expression = expression.replace(old, new)

layersDict[nameToMap] = lyr

# need return the modified expression because it's not a reference
return expression

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