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[processing] new tool: random points in layer bounds
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 bfc33ba commit 1b423ca29f075abfa6a00d01fcaaa5030ee3e11d
@@ -91,6 +91,7 @@
from PointsFromPolygons import PointsFromPolygons
from PointsFromLines import PointsFromLines
from RandomPointsExtent import RandomPointsExtent
from RandomPointsLayer import RandomPointsLayer

# from VectorLayerHistogram import VectorLayerHistogram
# from VectorLayerScatterplot import VectorLayerScatterplot
@@ -144,6 +145,7 @@ def __init__(self):
RasterLayerStatistics(), PointsDisplacement(),
ZonalStatistics(), PointsFromPolygons(),
PointsFromLines(), RandomPointsExtent(),
RandomPointsLayer(),
# ------ raster ------
# CreateConstantRaster(),
# ------ graphics ------
@@ -0,0 +1,133 @@
# -*- coding: utf-8 -*-

"""
***************************************************************************
RandomPointsLayer.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.outputs.OutputVector import OutputVector
from processing.tools import dataobjects, vector


class RandomPointsLayer(GeoAlgorithm):

VECTOR = 'VECTOR'
POINT_NUMBER = 'POINT_NUMBER'
MIN_DISTANCE = 'MIN_DISTANCE'
OUTPUT = 'OUTPUT'

def defineCharacteristics(self):
self.name = 'Random points in layer bounds'
self.group = 'Vector creation tools'
self.addParameter(ParameterVector(self.VECTOR,
'Input layer',[ParameterVector.VECTOR_TYPE_POLYGON]))
self.addParameter(
ParameterNumber(self.POINT_NUMBER, 'Points number', 1, 9999999, 1))
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))
pointCount = int(self.getParameterValue(self.POINT_NUMBER))
minDistance = float(self.getParameterValue(self.MIN_DISTANCE))

bbox = layer.extent()
extent = QgsGeometry().fromRect(bbox)
idxLayer = vector.spatialindex(layer)

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

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

index = QgsSpatialIndex()
points = dict()

request = QgsFeatureRequest()

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)
ids = idxLayer.intersects(geom.buffer(5, 5).boundingBox())
if len(ids) > 0 and \
self.checkMinDistance(pnt, index, minDistance, points):
for i in ids:
f = layer.getFeatures(request.setFilterFid(i)).next()
tmpGeom = QgsGeometry(f.geometry())
if geom.within(tmpGeom):
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.')

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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