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This algorithm updates existing geometries (or creates new geometries) for input features by use of a QGIS expression. This allows complex geometry modifications which can utilise all the flexibility of the QGIS expression engine to manipulate and create geometries for output features.
130 lines
5.3 KiB
Python
130 lines
5.3 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, QgsExpression, QgsExpressionContext, QgsExpressionContextUtils, QgsGeometry
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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.ProcessingLog import ProcessingLog
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from processing.core.parameters import ParameterVector, ParameterSelection, ParameterBoolean, ParameterString
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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 defineCharacteristics(self):
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self.name, self.i18n_name = self.trAlgorithm('Geometry by expression')
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self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
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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(ParameterString(self.EXPRESSION,
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self.tr("Geometry expression"), '$geometry'))
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self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Modified geometry')))
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def processAlgorithm(self, progress):
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layer = dataobjects.getObjectFromUri(
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self.getParameterValue(self.INPUT_LAYER))
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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(
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layer.fields(),
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wkb_type,
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layer.crs())
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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()
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exp_context.appendScope(QgsExpressionContextUtils.globalScope())
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exp_context.appendScope(QgsExpressionContextUtils.projectScope())
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exp_context.appendScope(QgsExpressionContextUtils.layerScope(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: %s' % expression.evalErrorString()))
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features = vector.features(layer)
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total = 100.0 / len(features)
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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: %s' % 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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progress.setPercentage(int(current * total))
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del writer
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