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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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alexbruy committed May 16, 2014
1 parent 1b423ca commit 72997dca6d111119885b9cfb07c7856a0bdada57
@@ -92,6 +92,7 @@
from PointsFromLines import PointsFromLines
from RandomPointsExtent import RandomPointsExtent
from RandomPointsLayer import RandomPointsLayer
from RandomPointsPolygonsFixed import RandomPointsPolygonsFixed

# from VectorLayerHistogram import VectorLayerHistogram
# from VectorLayerScatterplot import VectorLayerScatterplot
@@ -145,7 +146,7 @@ def __init__(self):
RasterLayerStatistics(), PointsDisplacement(),
ZonalStatistics(), PointsFromPolygons(),
PointsFromLines(), RandomPointsExtent(),
RandomPointsLayer(),
RandomPointsLayer(), RandomPointsPolygonsFixed(),
# ------ raster ------
# CreateConstantRaster(),
# ------ graphics ------
@@ -0,0 +1,146 @@
# -*- coding: utf-8 -*-

"""
***************************************************************************
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. *
* *
***************************************************************************
"""

__author__ = 'Alexander Bruy'
__date__ = 'April 2014'
__copyright__ = '(C) 2014, Alexander Bruy'

# This will get replaced with a git SHA1 when you do a git archive

__revision__ = '$Format:%H$'

import math
import random

from PyQt4.QtCore import *

from qgis.core import *

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


class RandomPointsPolygonsFixed(GeoAlgorithm):

VECTOR = 'VECTOR'
VALUE = 'VALUE'
MIN_DISTANCE = 'MIN_DISTANCE'
STRATEGY = 'STRATEGY'
OUTPUT = 'OUTPUT'

STRATEGIES = ['Points count',
'Points density'
]

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'))

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)

fields = QgsFields()
fields.append(QgsField('id', QVariant.Int, '', 10, 0))
writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
fields, QGis.WKBPoint, layer.dataProvider().crs())


request = QgsFeatureRequest()

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)))

index = QgsSpatialIndex()
points = dict()

nPoints = 0
nIterations = 0
maxIterations = pointCount * 200
total = 100.0 / pointCount

while nIterations < maxIterations and nPoints < pointCount:
rx = bbox.xMinimum() + bbox.width() * random.random()
ry = bbox.yMinimum() + bbox.height() * random.random()

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

if nPoints < pointCount:
ProcessingLog.addToLog(
ProcessingLog.LOG_INFO,
'Can not generate requested number of random points. Maximum '
'number of attempts exceeded.')

progress.setPercentage(0)

del writer

def checkMinDistance(self, point, index, distance, points):
if distance == 0:
return True

neighbors = index.nearestNeighbor(point, 1)
if len(neighbors) == 0:
return True

if neighbors[0] in points:
np = points[neighbors[0]]
if np.sqrDist(point) < (distance * distance):
return False

return True

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