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2374c80e3a
Work done for Faunalia funded by Prof. António Mira (University of Évora, Portugal, Unidade de Biologia da Conservação) and Dr. Rosana Peixoto
140 lines
5.1 KiB
Python
140 lines
5.1 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 math
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import random
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from PyQt4.QtCore import *
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from qgis.core import *
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from processing import interface
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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.parameters.ParameterVector import ParameterVector
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from processing.parameters.ParameterNumber import ParameterNumber
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from processing.parameters.ParameterSelection import ParameterSelection
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from processing.outputs.OutputVector 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 = 'Random points along line'
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self.group = 'Vector creation tools'
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self.addParameter(ParameterVector(self.VECTOR,
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'Input layer',[ParameterVector.VECTOR_TYPE_LINE]))
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self.addParameter(ParameterNumber
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(self.POINT_NUMBER, 'Number of points', 1, 9999999, 1))
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self.addParameter(ParameterNumber(
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self.MIN_DISTANCE, 'Minimum distance', 0.0, 9999999.0, 0.0))
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self.addOutput(OutputVector(self.OUTPUT, '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(
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ProcessingLog.LOG_INFO,
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'Can not generate requested number of random points. Maximum '
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'number of attempts exceeded.')
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del writer
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