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Since it's safe to evaluate parameters in background threads now, it's usually going to be ok to evaluate everything in the processAlgorithm step. This keeps the algorithm code as simple as possible, and will make porting faster. Note that the prepare/postProcess virtual methods still exist and can be used when an algorithm MUST do setup/cleanup work in the main thread.
125 lines
5.0 KiB
Python
125 lines
5.0 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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SimplifyGeometries.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 archive
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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 (QgsMapToPixelSimplifier,
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QgsMessageLog,
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QgsFeatureSink,
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QgsProcessingUtils,
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QgsProcessingParameterFeatureSource,
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QgsProcessingParameterFeatureSink,
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QgsProcessingParameterEnum,
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QgsProcessingParameterNumber,
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QgsProcessingOutputVectorLayer)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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from processing.tools import dataobjects
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pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]
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class SimplifyGeometries(QgisAlgorithm):
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INPUT = 'INPUT'
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TOLERANCE = 'TOLERANCE'
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OUTPUT = 'OUTPUT'
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METHOD = 'METHOD'
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def icon(self):
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return QIcon(os.path.join(pluginPath, 'images', 'ftools', 'simplify.png'))
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def group(self):
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return self.tr('Vector geometry tools')
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def __init__(self):
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super().__init__()
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self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT,
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self.tr('Input layer'),
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[dataobjects.TYPE_VECTOR_POLYGON, dataobjects.TYPE_VECTOR_LINE]))
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self.methods = [self.tr('Distance (Douglas-Peucker)'),
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'Snap to grid',
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'Area (Visvalingam)']
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self.addParameter(QgsProcessingParameterEnum(
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self.METHOD,
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self.tr('Simplification method'),
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self.methods, defaultValue=0))
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self.addParameter(QgsProcessingParameterNumber(self.TOLERANCE,
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self.tr('Tolerance'), minValue=0.0, maxValue=10000000.0, defaultValue=1.0))
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self.addParameter(QgsProcessingParameterFeatureSink(self.OUTPUT, self.tr('Simplified')))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr('Simplified')))
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def name(self):
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return 'simplifygeometries'
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def displayName(self):
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return self.tr('Simplify geometries')
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def processAlgorithm(self, parameters, context, feedback):
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source = self.parameterAsSource(parameters, self.INPUT, context)
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tolerance = self.parameterAsDouble(parameters, self.TOLERANCE, context)
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method = self.parameterAsEnum(parameters, self.METHOD, context)
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pointsBefore = 0
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pointsAfter = 0
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(sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
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source.fields(), source.wkbType(), source.sourceCrs())
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features = source.getFeatures()
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total = 100.0 / source.featureCount() if source.featureCount() else 0
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if method != 0:
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simplifier = QgsMapToPixelSimplifier(QgsMapToPixelSimplifier.SimplifyGeometry, tolerance, method)
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for current, input_feature in enumerate(features):
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if feedback.isCanceled():
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break
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out_feature = input_feature
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if input_feature.geometry():
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input_geometry = input_feature.geometry()
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pointsBefore += input_geometry.geometry().nCoordinates()
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if method == 0: # distance
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output_geometry = input_geometry.simplify(tolerance)
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else:
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output_geometry = simplifier.simplify(input_geometry)
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pointsAfter += output_geometry.geometry().nCoordinates()
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out_feature.setGeometry(output_geometry)
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sink.addFeature(out_feature, QgsFeatureSink.FastInsert)
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feedback.setProgress(int(current * total))
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QgsMessageLog.logMessage(self.tr('Simplify: Input geometries have been simplified from {0} to {1} points').format(pointsBefore, pointsAfter),
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self.tr('Processing'), QgsMessageLog.INFO)
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return {self.OUTPUT: dest_id}
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