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This change allows users to choose which method to use when running the simplify geometries algorithm, with choices of the existing distance based (Douglas Peucker) algorithm, area based (Visvalingam) algorithm and snap-to-grid. Visvaligam in particular usually results in more cartographically pleasing simplification over the standard distance based methods.
111 lines
4.4 KiB
Python
111 lines
4.4 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 Qgis, QgsFeature, QgsGeometry, QgsWkbTypes, QgsMapToPixelSimplifier
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.ProcessingLog import ProcessingLog
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from processing.core.parameters import ParameterVector
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from processing.core.parameters import ParameterNumber
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from processing.core.parameters import ParameterSelection
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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 SimplifyGeometries(GeoAlgorithm):
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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 getIcon(self):
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return QIcon(os.path.join(pluginPath, 'images', 'ftools', 'simplify.png'))
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def defineCharacteristics(self):
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self.name, self.i18n_name = self.trAlgorithm('Simplify geometries')
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self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
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self.addParameter(ParameterVector(self.INPUT,
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self.tr('Input layer'),
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[ParameterVector.VECTOR_TYPE_POLYGON, ParameterVector.VECTOR_TYPE_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(ParameterSelection(
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self.METHOD,
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self.tr('Simplification method'),
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self.methods, default=0))
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self.addParameter(ParameterNumber(self.TOLERANCE,
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self.tr('Tolerance'), 0.0, 10000000.0, 1.0))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Simplified')))
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def processAlgorithm(self, progress):
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layer = dataobjects.getObjectFromUri(self.getParameterValue(self.INPUT))
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tolerance = self.getParameterValue(self.TOLERANCE)
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method = self.getParameterValue(self.METHOD)
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pointsBefore = 0
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pointsAfter = 0
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writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
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layer.fields().toList(), layer.wkbType(), layer.crs())
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features = vector.features(layer)
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total = 100.0 / len(features)
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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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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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writer.addFeature(out_feature)
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progress.setPercentage(int(current * total))
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del writer
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ProcessingLog.addToLog(ProcessingLog.LOG_INFO,
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self.tr('Simplify: Input geometries have been simplified from %s to %s points' % (pointsBefore, pointsAfter)))
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