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[processing] new tool: random points within polygons
Work done for Faunalia funded by Prof. António Mira (University of Évora, Portugal, Unidade de Biologia da Conservação) and Dr. Rosana Peixoto
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python/plugins/processing/algs/qgis/RandomPointsPolygonsFixed.py
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# -*- coding: utf-8 -*- | ||
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""" | ||
*************************************************************************** | ||
RandomPointsPolygonsFixed.py | ||
--------------------- | ||
Date : April 2014 | ||
Copyright : (C) 2014 by Alexander Bruy | ||
Email : alexander dot bruy at gmail dot com | ||
*************************************************************************** | ||
* * | ||
* This program is free software; you can redistribute it and/or modify * | ||
* it under the terms of the GNU General Public License as published by * | ||
* the Free Software Foundation; either version 2 of the License, or * | ||
* (at your option) any later version. * | ||
* * | ||
*************************************************************************** | ||
""" | ||
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__author__ = 'Alexander Bruy' | ||
__date__ = 'April 2014' | ||
__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 | ||
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 | ||
from processing.core.GeoAlgorithm import GeoAlgorithm | ||
from processing.core.ProcessingLog import ProcessingLog | ||
from processing.parameters.ParameterVector import ParameterVector | ||
from processing.parameters.ParameterNumber import ParameterNumber | ||
from processing.parameters.ParameterSelection import ParameterSelection | ||
from processing.outputs.OutputVector import OutputVector | ||
from processing.tools import dataobjects, vector | ||
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class RandomPointsPolygonsFixed(GeoAlgorithm): | ||
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VECTOR = 'VECTOR' | ||
VALUE = 'VALUE' | ||
MIN_DISTANCE = 'MIN_DISTANCE' | ||
STRATEGY = 'STRATEGY' | ||
OUTPUT = 'OUTPUT' | ||
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STRATEGIES = ['Points count', | ||
'Points density' | ||
] | ||
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def defineCharacteristics(self): | ||
self.name = 'Random points inside polygons' | ||
self.group = 'Vector creation tools' | ||
self.addParameter(ParameterVector(self.VECTOR, | ||
'Input layer',[ParameterVector.VECTOR_TYPE_POLYGON])) | ||
self.addParameter(ParameterSelection( | ||
self.STRATEGY, 'Sampling strategy', self.STRATEGIES, 0)) | ||
self.addParameter( | ||
ParameterNumber(self.VALUE, 'Number or density of points', 0.0001, 9999999.0, 1.0)) | ||
self.addParameter(ParameterNumber( | ||
self.MIN_DISTANCE, 'Minimum distance', 0.0, 9999999, 0.0)) | ||
self.addOutput(OutputVector(self.OUTPUT, 'Random points')) | ||
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def processAlgorithm(self, progress): | ||
layer = dataobjects.getObjectFromUri( | ||
self.getParameterValue(self.VECTOR)) | ||
value = float(self.getParameterValue(self.VALUE)) | ||
minDistance = float(self.getParameterValue(self.MIN_DISTANCE)) | ||
strategy = self.getParameterValue(self.STRATEGY) | ||
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fields = QgsFields() | ||
fields.append(QgsField('id', QVariant.Int, '', 10, 0)) | ||
writer = self.getOutputFromName(self.OUTPUT).getVectorWriter( | ||
fields, QGis.WKBPoint, layer.dataProvider().crs()) | ||
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request = QgsFeatureRequest() | ||
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da = QgsDistanceArea() | ||
features = vector.features(layer) | ||
for current, f in enumerate(features): | ||
fGeom = QgsGeometry(f.geometry()) | ||
bbox = fGeom.boundingBox() | ||
if strategy == 0: | ||
pointCount = int(value) | ||
else: | ||
pointCount = int(round(value * da.measure(fGeom))) | ||
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index = QgsSpatialIndex() | ||
points = dict() | ||
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nPoints = 0 | ||
nIterations = 0 | ||
maxIterations = pointCount * 200 | ||
total = 100.0 / pointCount | ||
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while nIterations < maxIterations and nPoints < pointCount: | ||
rx = bbox.xMinimum() + bbox.width() * random.random() | ||
ry = bbox.yMinimum() + bbox.height() * random.random() | ||
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pnt = QgsPoint(rx, ry) | ||
geom = QgsGeometry.fromPoint(pnt) | ||
if geom.within(fGeom) and \ | ||
self.checkMinDistance(pnt, index, minDistance, points): | ||
f = QgsFeature(nPoints) | ||
f.initAttributes(1) | ||
f.setFields(fields) | ||
f.setAttribute('id', nPoints) | ||
f.setGeometry(geom) | ||
writer.addFeature(f) | ||
index.insertFeature(f) | ||
points[nPoints] = pnt | ||
nPoints += 1 | ||
progress.setPercentage(int(nPoints * total)) | ||
nIterations += 1 | ||
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if nPoints < pointCount: | ||
ProcessingLog.addToLog( | ||
ProcessingLog.LOG_INFO, | ||
'Can not generate requested number of random points. Maximum ' | ||
'number of attempts exceeded.') | ||
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progress.setPercentage(0) | ||
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del writer | ||
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def checkMinDistance(self, point, index, distance, points): | ||
if distance == 0: | ||
return True | ||
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neighbors = index.nearestNeighbor(point, 1) | ||
if len(neighbors) == 0: | ||
return True | ||
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if neighbors[0] in points: | ||
np = points[neighbors[0]] | ||
if np.sqrDist(point) < (distance * distance): | ||
return False | ||
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return True |