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136 lines
5.3 KiB
Python
136 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 PyQt4.QtCore import QVariant
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from qgis.core import QGis, QgsFields, QgsField, QgsGeometry, QgsSpatialIndex, QgsDistanceArea, QgsFeatureRequest, QgsFeature, 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, QGis.WKBPoint, layer.dataProvider().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 = QgsGeometry(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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