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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.
102 lines
3.6 KiB
Python
102 lines
3.6 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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PolygonCentroids.py
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---------------------
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Date : August 2012
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Copyright : (C) 2012 by Victor Olaya
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Email : volayaf 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__ = 'Victor Olaya'
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__date__ = 'August 2012'
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__copyright__ = '(C) 2012, Victor Olaya'
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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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import os
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from qgis.PyQt.QtGui import QIcon
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from qgis.core import (QgsProcessingAlgorithm,
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QgsGeometry,
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QgsFeature,
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QgsWkbTypes,
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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
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from processing.core.outputs import OutputVector
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from processing.tools import dataobjects, vector
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pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]
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class PolygonCentroids(GeoAlgorithm):
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INPUT_LAYER = 'INPUT_LAYER'
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OUTPUT_LAYER = 'OUTPUT_LAYER'
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def flags(self):
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# this algorithm is deprecated - use Centroids instead
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return QgsProcessingAlgorithm.FlagDeprecated
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def icon(self):
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return QIcon(os.path.join(pluginPath, 'images', 'ftools', 'centroids.png'))
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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 'polygoncentroids'
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def displayName(self):
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return self.tr('Polygon centroids')
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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'), [dataobjects.TYPE_VECTOR_POLYGON]))
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self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Centroids')))
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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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writer = self.getOutputFromName(
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self.OUTPUT_LAYER).getVectorWriter(layer.fields(), QgsWkbTypes.Point, layer.crs(), context)
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outFeat = QgsFeature()
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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, feat in enumerate(features):
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inGeom = feat.geometry()
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attrs = feat.attributes()
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if inGeom.isNull():
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outGeom = QgsGeometry(None)
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else:
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outGeom = QgsGeometry(inGeom.centroid())
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if not outGeom:
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raise GeoAlgorithmExecutionException(
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self.tr('Error calculating centroid'))
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outFeat.setGeometry(outGeom)
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outFeat.setAttributes(attrs)
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writer.addFeature(outFeat)
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feedback.setProgress(int(current * total))
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del writer
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