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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.
121 lines
4.8 KiB
Python
121 lines
4.8 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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PointsAlongGeometry.py
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---------------------
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Date : August 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__ = 'August 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 archive
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__revision__ = '$Format:%H$'
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import os
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import math
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from qgis.PyQt.QtCore import QVariant
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from qgis.PyQt.QtGui import QIcon
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from qgis.core import QgsFeature, QgsWkbTypes, QgsField, QgsProcessingUtils
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.parameters import ParameterVector, ParameterNumber
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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 PointsAlongGeometry(GeoAlgorithm):
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INPUT = 'INPUT'
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OUTPUT = 'OUTPUT'
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DISTANCE = 'DISTANCE'
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START_OFFSET = 'START_OFFSET'
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END_OFFSET = 'END_OFFSET'
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def icon(self):
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return QIcon(os.path.join(pluginPath, 'images', 'ftools', 'extract_nodes.png'))
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def tags(self):
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return self.tr('create,interpolate,points,lines').split(',')
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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 'pointsalonglines'
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def displayName(self):
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return self.tr('Points along lines')
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def defineCharacteristics(self):
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self.addParameter(ParameterVector(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.addParameter(ParameterNumber(self.DISTANCE,
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self.tr('Distance'), default=1.0))
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self.addParameter(ParameterNumber(self.START_OFFSET,
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self.tr('Start offset'), default=0.0))
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self.addParameter(ParameterNumber(self.END_OFFSET,
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self.tr('End offset'), default=0.0))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Points'), datatype=[dataobjects.TYPE_VECTOR_POINT]))
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def processAlgorithm(self, context, feedback):
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layer = dataobjects.QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
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distance = self.getParameterValue(self.DISTANCE)
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start_offset = self.getParameterValue(self.START_OFFSET)
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end_offset = self.getParameterValue(self.END_OFFSET)
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fields = layer.fields()
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fields.append(QgsField('distance', QVariant.Double))
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fields.append(QgsField('angle', QVariant.Double))
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writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields, QgsWkbTypes.Point, layer.crs(), context)
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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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input_geometry = input_feature.geometry()
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if not input_geometry:
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writer.addFeature(input_feature)
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else:
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if input_geometry.type == QgsWkbTypes.PolygonGeometry:
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length = input_geometry.geometry().perimeter()
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else:
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length = input_geometry.length() - end_offset
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current_distance = start_offset
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while current_distance <= length:
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point = input_geometry.interpolate(current_distance)
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angle = math.degrees(input_geometry.interpolateAngle(current_distance))
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output_feature = QgsFeature()
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output_feature.setGeometry(point)
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attrs = input_feature.attributes()
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attrs.append(current_distance)
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attrs.append(angle)
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output_feature.setAttributes(attrs)
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writer.addFeature(output_feature)
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current_distance += distance
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feedback.setProgress(int(current * total))
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del writer
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