QGIS/python/plugins/sextante/ftools/Delaunay.py

import os.path
from sets import Set

from PyQt4 import QtGui
from PyQt4.QtCore import *

from qgis.core import *

from sextante.core.GeoAlgorithm import GeoAlgorithm
from sextante.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from sextante.core.QGisLayers import QGisLayers

from sextante.parameters.ParameterVector import ParameterVector
from sextante.outputs.OutputVector import OutputVector

from sextante.ftools import voronoi

class Delaunay(GeoAlgorithm):

    INPUT = "INPUT"
    OUTPUT = "OUTPUT"

    def getIcon(self):
        return QtGui.QIcon(os.path.dirname(__file__) + "/icons/delaunay.png")

    def defineCharacteristics(self):
        self.name = "Delaunay triangulation"
        self.group = "Geometry tools"

        self.addParameter(ParameterVector(self.INPUT, "Input layer", ParameterVector.VECTOR_TYPE_POINT))

        self.addOutput(OutputVector(self.OUTPUT, "Delaunay triangulation"))

    def processAlgorithm(self, progress):
        settings = QSettings()
        encoding = settings.value( "/UI/encoding", "System" ).toString()

        layer = QGisLayers.getObjectFromUri(self.getParameterValue(self.INPUT))
        output = self.getOutputValue(self.OUTPUT)

        provider = layer.dataProvider()
        provider.select()

        fields = {0 : QgsField("POINTA", QVariant.Double, "", 24, 15),
                  1 : QgsField("POINTB", QVariant.Double, "", 24, 15),
                  2 : QgsField("POINTC", QVariant.Double, "", 24, 15)
                 }

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields,
                     QGis.WKBPolygon, provider.crs())

        pts = []
        ptDict = {}
        ptNdx = -1
        inFeat = QgsFeature()
        c = voronoi.Context()

        while provider.nextFeature(inFeat):
            geom = QgsGeometry(inFeat.geometry())
            point = geom.asPoint()
            x = point.x()
            y = point.y()
            pts.append((x, y))
            ptNdx +=1
            ptDict[ptNdx] = inFeat.id()

        if len(pts) < 3:
            raise GeoAlgorithmExecutionException("Input file should contain at least 3 points. Choose another file and try again.")

        uniqueSet = Set(item for item in pts)
        ids = [pts.index(item) for item in uniqueSet]
        sl = voronoi.SiteList([voronoi.Site(*i) for i in uniqueSet])
        c.triangulate = True
        voronoi.voronoi(sl, c)
        triangles = c.triangles
        feat = QgsFeature()

        current = 0
        total = 100.0 / float(len(triangles))

        for triangle in triangles:
            indicies = list(triangle)
            indicies.append(indicies[0])
            polygon = []
            step = 0

            for index in indicies:
                provider.featureAtId(ptDict[ids[index]], inFeat, True)
                geom = QgsGeometry(inFeat.geometry())
                point = QgsPoint(geom.asPoint())
                polygon.append(point)
                if step <= 3:
                    feat.addAttribute(step, QVariant(ids[index]))
                step += 1

            geometry = QgsGeometry().fromPolygon([polygon])
            feat.setGeometry(geometry)
            writer.addFeature(feat)
            current += 1
            progress.setPercentage(int(current * total))

        del writer