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ConcaveHull.py
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ConcaveHull.py
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# -*- coding: utf-8 -*-
"""
***************************************************************************
ConcaveHull.py
---------------------
Date : May 2014
Copyright : (C) 2012 by Piotr Pociask
Email : piotr dot pociask at gis-support dot pl
***************************************************************************
* *
* 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. *
* *
***************************************************************************
"""
from builtins import range
__author__ = 'Piotr Pociask'
__date__ = 'May 2014'
__copyright__ = '(C) 2014, Piotr Pociask'
# This will get replaced with a git SHA1 when you do a git archive
__revision__ = '$Format:%H$'
from qgis.core import Qgis, QgsFeatureRequest, QgsFeature, QgsGeometry, QgsWkbTypes
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterVector
from processing.core.parameters import ParameterNumber
from processing.core.parameters import ParameterBoolean
from processing.core.outputs import OutputVector
from processing.tools import dataobjects
import processing
from math import sqrt
class ConcaveHull(GeoAlgorithm):
INPUT = 'INPUT'
ALPHA = 'ALPHA'
HOLES = 'HOLES'
NO_MULTIGEOMETRY = 'NO_MULTIGEOMETRY'
OUTPUT = 'OUTPUT'
def defineCharacteristics(self):
self.name, self.i18n_name = self.trAlgorithm('Concave hull')
self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
self.addParameter(ParameterVector(ConcaveHull.INPUT,
self.tr('Input point layer'), [dataobjects.TYPE_VECTOR_POINT]))
self.addParameter(ParameterNumber(self.ALPHA,
self.tr('Threshold (0-1, where 1 is equivalent with Convex Hull)'),
0, 1, 0.3))
self.addParameter(ParameterBoolean(self.HOLES,
self.tr('Allow holes'), True))
self.addParameter(ParameterBoolean(self.NO_MULTIGEOMETRY,
self.tr('Split multipart geometry into singleparts geometries'), False))
self.addOutput(OutputVector(ConcaveHull.OUTPUT, self.tr('Concave hull'), datatype=[dataobjects.TYPE_VECTOR_POLYGON]))
def processAlgorithm(self, progress):
layer = dataobjects.getObjectFromUri(self.getParameterValue(ConcaveHull.INPUT))
alpha = self.getParameterValue(self.ALPHA)
holes = self.getParameterValue(self.HOLES)
no_multigeom = self.getParameterValue(self.NO_MULTIGEOMETRY)
# Delaunay triangulation from input point layer
progress.setText(self.tr('Creating Delaunay triangles...'))
delone_triangles = processing.runalg("qgis:delaunaytriangulation", layer, None)['OUTPUT']
delaunay_layer = processing.getObject(delone_triangles)
# Get max edge length from Delaunay triangles
progress.setText(self.tr('Computing edges max length...'))
features = delaunay_layer.getFeatures()
if len(features) == 0:
raise GeoAlgorithmExecutionException(self.tr('No Delaunay triangles created.'))
counter = 50. / len(features)
lengths = []
edges = {}
for feat in features:
line = feat.geometry().asPolygon()[0]
for i in range(len(line) - 1):
lengths.append(sqrt(line[i].sqrDist(line[i + 1])))
edges[feat.id()] = max(lengths[-3:])
progress.setPercentage(feat.id() * counter)
max_length = max(lengths)
# Get features with longest edge longer than alpha*max_length
progress.setText(self.tr('Removing features...'))
counter = 50. / len(edges)
i = 0
ids = []
for id, max_len in list(edges.items()):
if max_len > alpha * max_length:
ids.append(id)
progress.setPercentage(50 + i * counter)
i += 1
# Remove features
delaunay_layer.selectByIds(ids)
delaunay_layer.startEditing()
delaunay_layer.deleteSelectedFeatures()
delaunay_layer.commitChanges()
# Dissolve all Delaunay triangles
progress.setText(self.tr('Dissolving Delaunay triangles...'))
dissolved = processing.runalg("qgis:dissolve", delaunay_layer,
True, None, None)['OUTPUT']
dissolved_layer = processing.getObject(dissolved)
# Save result
progress.setText(self.tr('Saving data...'))
feat = QgsFeature()
dissolved_layer.getFeatures(QgsFeatureRequest().setFilterFid(0)).nextFeature(feat)
writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
layer.fields().toList(), QgsWkbTypes.Polygon, layer.crs())
geom = feat.geometry()
if no_multigeom and geom.isMultipart():
# Only singlepart geometries are allowed
geom_list = geom.asMultiPolygon()
for single_geom_list in geom_list:
single_feature = QgsFeature()
single_geom = QgsGeometry.fromPolygon(single_geom_list)
if not holes:
# Delete holes
deleted = True
while deleted:
deleted = single_geom.deleteRing(1)
single_feature.setGeometry(single_geom)
writer.addFeature(single_feature)
else:
# Multipart geometries are allowed
if not holes:
# Delete holes
deleted = True
while deleted:
deleted = geom.deleteRing(1)
writer.addFeature(feat)
del writer