QGIS/python/plugins/processing/algs/ftools/Difference.py

# -*- coding: utf-8 -*-

"""
***************************************************************************
    Difference.py
    ---------------------
    Date                 : August 2012
    Copyright            : (C) 2012 by Victor Olaya
    Email                : volayaf 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__ = 'Victor Olaya'
__date__ = 'August 2012'
__copyright__ = '(C) 2012, Victor Olaya'
# This will get replaced with a git SHA1 when you do a git archive
__revision__ = '$Format:%H$'

from PyQt4.QtCore import *

from qgis.core import *

from processing.core.QGisLayers import QGisLayers
from processing.core.ProcessingLog import ProcessingLog
from processing.core.GeoAlgorithm import GeoAlgorithm

from processing.parameters.ParameterVector import ParameterVector

from processing.outputs.OutputVector import OutputVector

from processing.algs.ftools import FToolsUtils as utils

class Difference(GeoAlgorithm):

    INPUT = "INPUT"
    OVERLAY = "OVERLAY"
    OUTPUT = "OUTPUT"

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

    def defineCharacteristics(self):
        self.name = "Difference"
        self.group = "Vector overlay tools"
        self.addParameter(ParameterVector(Difference.INPUT, "Input layer", [ParameterVector.VECTOR_TYPE_ANY]))
        self.addParameter(ParameterVector(Difference.OVERLAY, "Difference layer", [ParameterVector.VECTOR_TYPE_ANY]))
        self.addOutput(OutputVector(Difference.OUTPUT, "Difference"))

    def processAlgorithm(self, progress):
        layerA = QGisLayers.getObjectFromUri(self.getParameterValue(Difference.INPUT))
        layerB = QGisLayers.getObjectFromUri(self.getParameterValue(Difference.OVERLAY))

        GEOS_EXCEPT = True

        FEATURE_EXCEPT = True

        writer = self.getOutputFromName(Difference.OUTPUT).getVectorWriter(layerA.pendingFields(),
                     layerA.dataProvider().geometryType(), layerA.dataProvider().crs())

        inFeatA = QgsFeature()
        inFeatB = QgsFeature()
        outFeat = QgsFeature()

        index = utils.createSpatialIndex(layerB)

        selectionA = QGisLayers.features(layerA)

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

        for inFeatA in selectionA:
            add = True
            geom = QgsGeometry(inFeatA.geometry())
            diff_geom = QgsGeometry(geom)
            attrs = inFeatA.attributes()
            intersections = index.intersects(geom.boundingBox())
            for i in intersections:
                request = QgsFeatureRequest().setFilterFid(i)
                inFeatB = layerB.getFeatures(request).next()
                tmpGeom = QgsGeometry(inFeatB.geometry())
                try:
                    if diff_geom.intersects(tmpGeom):
                        diff_geom = QgsGeometry(diff_geom.difference(tmpGeom))
                except:
                    GEOS_EXCEPT = False
                    add = False
                    break

            if add:
                try:
                    outFeat.setGeometry(diff_geom)
                    outFeat.setAttributes(attrs)
                    writer.addFeature(outFeat)
                except:
                    FEATURE_EXCEPT = False
                    continue

            current += 1
            progress.setPercentage(int(current * total))

        del writer

        if not GEOS_EXCEPT:
            ProcessingLog.addToLog(ProcessingLog.LOG_WARNING, "Geometry exception while computing difference")
        if not FEATURE_EXCEPT:
            ProcessingLog.addToLog(ProcessingLog.LOG_WARNING, "Feature exception while computing difference")