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Algorithms and other processing code should use this method (instead of dataobjects.getLayerFromString) to retrieve layers from a string, as it considers the processing context and allows resolving strings to temporarily stored layers. This permits processing models to function correctly when intermediate results are stored as memory layers. Subsequent model algorithms can then access these temporary layers as inputs. All temporary layers will be removed when the context object is destroyed after the model algorithm is run.
140 lines
5.6 KiB
Python
140 lines
5.6 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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GeometryByExpression.py
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-----------------------
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Date : October 2016
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Copyright : (C) 2016 by Nyall Dawson
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Email : nyall dot dawson at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Nyall Dawson'
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__date__ = 'October 2016'
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__copyright__ = '(C) 2016, Nyall Dawson'
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# This will get replaced with a git SHA1 when you do a git archive323
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsWkbTypes,
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QgsExpression,
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QgsExpressionContext,
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QgsExpressionContextUtils,
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QgsGeometry,
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QgsApplication,
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QgsProcessingUtils)
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.core.parameters import ParameterVector, ParameterSelection, ParameterBoolean, ParameterExpression
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from processing.core.outputs import OutputVector
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from processing.tools import dataobjects, vector
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class GeometryByExpression(GeoAlgorithm):
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INPUT_LAYER = 'INPUT_LAYER'
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OUTPUT_LAYER = 'OUTPUT_LAYER'
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OUTPUT_GEOMETRY = 'OUTPUT_GEOMETRY'
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WITH_Z = 'WITH_Z'
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WITH_M = 'WITH_M'
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EXPRESSION = 'EXPRESSION'
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def icon(self):
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return QgsApplication.getThemeIcon("/providerQgis.svg")
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def svgIconPath(self):
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return QgsApplication.iconPath("providerQgis.svg")
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def group(self):
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return self.tr('Vector geometry tools')
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def name(self):
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return 'geometrybyexpression'
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def displayName(self):
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return self.tr('Geometry by expression')
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def defineCharacteristics(self):
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self.addParameter(ParameterVector(self.INPUT_LAYER,
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self.tr('Input layer')))
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self.geometry_types = [self.tr('Polygon'),
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'Line',
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'Point']
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self.addParameter(ParameterSelection(
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self.OUTPUT_GEOMETRY,
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self.tr('Output geometry type'),
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self.geometry_types, default=0))
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self.addParameter(ParameterBoolean(self.WITH_Z,
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self.tr('Output geometry has z dimension'), False))
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self.addParameter(ParameterBoolean(self.WITH_M,
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self.tr('Output geometry has m values'), False))
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self.addParameter(ParameterExpression(self.EXPRESSION,
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self.tr("Geometry expression"), '$geometry', parent_layer=self.INPUT_LAYER))
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self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Modified geometry')))
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def processAlgorithm(self, context, feedback):
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layer = dataobjects.QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT_LAYER), context)
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geometry_type = self.getParameterValue(self.OUTPUT_GEOMETRY)
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wkb_type = None
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if geometry_type == 0:
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wkb_type = QgsWkbTypes.Polygon
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elif geometry_type == 1:
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wkb_type = QgsWkbTypes.LineString
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else:
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wkb_type = QgsWkbTypes.Point
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if self.getParameterValue(self.WITH_Z):
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wkb_type = QgsWkbTypes.addZ(wkb_type)
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if self.getParameterValue(self.WITH_M):
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wkb_type = QgsWkbTypes.addM(wkb_type)
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writer = self.getOutputFromName(
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self.OUTPUT_LAYER).getVectorWriter(layer.fields(), wkb_type, layer.crs(), context)
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expression = QgsExpression(self.getParameterValue(self.EXPRESSION))
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if expression.hasParserError():
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raise GeoAlgorithmExecutionException(expression.parserErrorString())
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exp_context = QgsExpressionContext(QgsExpressionContextUtils.globalProjectLayerScopes(layer))
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if not expression.prepare(exp_context):
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raise GeoAlgorithmExecutionException(
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self.tr('Evaluation error: {0}').format(expression.evalErrorString()))
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features = QgsProcessingUtils.getFeatures(layer, context)
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total = 100.0 / QgsProcessingUtils.featureCount(layer, context)
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for current, input_feature in enumerate(features):
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output_feature = input_feature
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exp_context.setFeature(input_feature)
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value = expression.evaluate(exp_context)
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if expression.hasEvalError():
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raise GeoAlgorithmExecutionException(
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self.tr('Evaluation error: {0}').format(expression.evalErrorString()))
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if not value:
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output_feature.setGeometry(QgsGeometry())
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else:
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if not isinstance(value, QgsGeometry):
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raise GeoAlgorithmExecutionException(
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self.tr('{} is not a geometry').format(value))
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output_feature.setGeometry(value)
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writer.addFeature(output_feature)
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feedback.setProgress(int(current * total))
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del writer
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