Merge pull request #1333 from p0cisk/ConcaveHull

[Processing][Feature] Add Concave Hull algorithm

python/plugins/processing/algs/qgis/ConcaveHull.py

@@ -0,0 +1,132 @@
+# -*- 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.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__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 PyQt4.QtCore import *
+from PyQt4.QtGui import *
+from qgis.core import *
+from processing.core.GeoAlgorithm import GeoAlgorithm
+from processing.parameters.ParameterVector import ParameterVector
+from processing.parameters.ParameterNumber import ParameterNumber
+from processing.parameters.ParameterBoolean import ParameterBoolean
+from processing.outputs.OutputVector 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 = 'Concave hull'
+        self.group = 'Vector geometry tools'
+        self.addParameter(ParameterVector(ConcaveHull.INPUT, 'Input point layer',
+                          [ParameterVector.VECTOR_TYPE_POINT]))
+        self.addParameter(ParameterNumber(self.ALPHA,
+                            'Threshold (0-1, where 1 is equivalent with Convex Hull)', 0, 1, 0.3))
+        self.addParameter(ParameterBoolean(self.HOLES, 'Allow holes', True))
+        self.addParameter(ParameterBoolean(self.NO_MULTIGEOMETRY,
+                            'Split multipart geometry into singleparts geometries', False))
+        self.addOutput(OutputVector(ConcaveHull.OUTPUT, 'Convex hull'))
+
+    def processAlgorithm(self, progress):
+        #get parameters
+        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('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('Computing edges max length ...')
+        features = delaunay_layer.getFeatures()
+        counter = 50./delaunay_layer.featureCount()
+        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('Removing features ...')
+        counter = 50./len(edges)
+        i = 0
+        ids = []
+        for id, max_len in edges.iteritems():
+            if max_len > alpha*max_length:
+                ids.append(id)
+            progress.setPercentage(50+i*counter)
+            i += 1
+        #remove features
+        delaunay_layer.setSelectedFeatures(ids)
+        delaunay_layer.startEditing()
+        delaunay_layer.deleteSelectedFeatures()
+        delaunay_layer.commitChanges()
+        #dissolve all Delaunay triangles
+        progress.setText('Dissolving Delaunay triangles ...')
+        dissolved = processing.runalg("qgis:dissolve", delaunay_layer,
+                                      True, '', None)['OUTPUT']
+        dissolved_layer = processing.getObject(dissolved)
+        #save result
+        progress.setText('Saving data ...')
+        feat = QgsFeature()
+        dissolved_layer.getFeatures(QgsFeatureRequest().setFilterFid(0)).nextFeature(feat)
+        writer = self.getOutputFromName(
+                self.OUTPUT).getVectorWriter(layer.pendingFields().toList(),
+                                             QGis.WKBPolygon, 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

python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py

@@ -72,6 +72,7 @@
 
 from mmqgisx.MMQGISXAlgorithms import *
 
+from ConcaveHull import ConcaveHull
 from Polygonize import Polygonize
 from RasterLayerStatistics import RasterLayerStatistics
 from StatisticsByCategories import StatisticsByCategories
@@ -137,7 +138,7 @@ def __init__(self):
                         SaveSelectedFeatures(), JoinAttributes(),
                         AutoincrementalField(), Explode(), FieldsPyculator(),
                         EquivalentNumField(), PointsLayerFromTable(),
-                        StatisticsByCategories(), Polygonize(),
+                        StatisticsByCategories(), ConcaveHull(), Polygonize(),
                         RasterLayerStatistics(), PointsDisplacement(),
                         ZonalStatistics(), PointsFromPolygons(),
                         PointsFromLines(),