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06c4b07222
Since the layer has more complete knowledge of the crs (ie, when provider could not determine crs and user has selected it from the list), and also better knowledge of layer fields (virtual fields, joined fields) we should use these rather than the provider methods.
138 lines
5.3 KiB
Python
138 lines
5.3 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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RandomPointsAlongLines.py
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---------------------
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Date : April 2014
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Copyright : (C) 2014 by Alexander Bruy
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Email : alexander dot bruy 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__ = 'Alexander Bruy'
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__date__ = 'April 2014'
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__copyright__ = '(C) 2014, Alexander Bruy'
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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 random
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from qgis.PyQt.QtCore import QVariant
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from qgis.core import (Qgis, QgsFields, QgsField, QgsGeometry, QgsSpatialIndex, QgsWkbTypes,
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QgsDistanceArea, QgsFeatureRequest, QgsFeature,
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QgsPoint)
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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.outputs import OutputVector
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from processing.tools import dataobjects, vector
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class RandomPointsAlongLines(GeoAlgorithm):
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VECTOR = 'VECTOR'
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POINT_NUMBER = 'POINT_NUMBER'
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MIN_DISTANCE = 'MIN_DISTANCE'
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OUTPUT = 'OUTPUT'
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def defineCharacteristics(self):
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self.name, self.i18n_name = self.trAlgorithm('Random points along line')
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self.group, self.i18n_group = self.trAlgorithm('Vector creation tools')
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self.addParameter(ParameterVector(self.VECTOR,
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self.tr('Input layer'), [ParameterVector.VECTOR_TYPE_LINE]))
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self.addParameter(ParameterNumber(self.POINT_NUMBER,
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self.tr('Number of points'), 1, None, 1))
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self.addParameter(ParameterNumber(self.MIN_DISTANCE,
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self.tr('Minimum distance'), 0.0, None, 0.0))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Random points')))
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def processAlgorithm(self, progress):
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layer = dataobjects.getObjectFromUri(
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self.getParameterValue(self.VECTOR))
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pointCount = float(self.getParameterValue(self.POINT_NUMBER))
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minDistance = float(self.getParameterValue(self.MIN_DISTANCE))
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fields = QgsFields()
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fields.append(QgsField('id', QVariant.Int, '', 10, 0))
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writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
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fields, QgsWkbTypes.Point, layer.crs())
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nPoints = 0
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nIterations = 0
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maxIterations = pointCount * 200
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featureCount = layer.featureCount()
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total = 100.0 / pointCount
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index = QgsSpatialIndex()
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points = dict()
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da = QgsDistanceArea()
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request = QgsFeatureRequest()
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random.seed()
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while nIterations < maxIterations and nPoints < pointCount:
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# pick random feature
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fid = random.randint(0, featureCount - 1)
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f = layer.getFeatures(request.setFilterFid(fid)).next()
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fGeom = f.geometry()
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if fGeom.isMultipart():
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lines = fGeom.asMultiPolyline()
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# pick random line
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lineId = random.randint(0, len(lines) - 1)
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vertices = lines[lineId]
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else:
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vertices = fGeom.asPolyline()
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# pick random segment
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if len(vertices) == 2:
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vid = 0
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else:
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vid = random.randint(0, len(vertices) - 2)
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startPoint = vertices[vid]
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endPoint = vertices[vid + 1]
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length = da.measureLine(startPoint, endPoint)
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dist = length * random.random()
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if dist > minDistance:
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d = dist / (length - dist)
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rx = (startPoint.x() + d * endPoint.x()) / (1 + d)
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ry = (startPoint.y() + d * endPoint.y()) / (1 + d)
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# generate random point
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pnt = QgsPoint(rx, ry)
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geom = QgsGeometry.fromPoint(pnt)
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if vector.checkMinDistance(pnt, index, minDistance, points):
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f = QgsFeature(nPoints)
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f.initAttributes(1)
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f.setFields(fields)
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f.setAttribute('id', nPoints)
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f.setGeometry(geom)
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writer.addFeature(f)
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index.insertFeature(f)
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points[nPoints] = pnt
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nPoints += 1
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progress.setPercentage(int(nPoints * total))
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nIterations += 1
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if nPoints < pointCount:
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ProcessingLog.addToLog(ProcessingLog.LOG_INFO,
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self.tr('Can not generate requested number of random points. '
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'Maximum number of attempts exceeded.'))
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del writer
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