QGIS/python/plugins/processing/algs/qgis/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__ = '$Format:%H$'

import os

from qgis.PyQt.QtGui import QIcon

from qgis.core import (QgsFeatureRequest,
                       QgsFeature,
                       QgsFeatureSink,
                       QgsGeometry,
                       QgsWkbTypes,
                       QgsMessageLog,
                       QgsProcessingUtils)
from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
from processing.core.parameters import ParameterVector
from processing.core.outputs import OutputVector

pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]


class Difference(QgisAlgorithm):

    INPUT = 'INPUT'
    OVERLAY = 'OVERLAY'
    IGNORE_INVALID = 'IGNORE_INVALID'
    OUTPUT = 'OUTPUT'

    def icon(self):
        return QIcon(os.path.join(pluginPath, 'images', 'ftools', 'difference.png'))

    def group(self):
        return self.tr('Vector overlay tools')

    def __init__(self):
        super().__init__()
        self.addParameter(ParameterVector(Difference.INPUT,
                                          self.tr('Input layer')))
        self.addParameter(ParameterVector(Difference.OVERLAY,
                                          self.tr('Difference layer')))
        self.addOutput(OutputVector(Difference.OUTPUT, self.tr('Difference')))

    def name(self):
        return 'difference'

    def displayName(self):
        return self.tr('Difference')

    def processAlgorithm(self, parameters, context, feedback):
        layerA = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(Difference.INPUT), context)
        layerB = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(Difference.OVERLAY), context)

        geomType = QgsWkbTypes.multiType(layerA.wkbType())
        writer = self.getOutputFromName(
            Difference.OUTPUT).getVectorWriter(layerA.fields(), geomType, layerA.crs(), context)

        outFeat = QgsFeature()
        index = QgsProcessingUtils.createSpatialIndex(layerB, context)
        selectionA = QgsProcessingUtils.getFeatures(layerA, context)
        total = 100.0 / layerA.featureCount() if layerA.featureCount() else 0
        for current, inFeatA in enumerate(selectionA):
            geom = inFeatA.geometry()
            diff_geom = QgsGeometry(geom)
            attrs = inFeatA.attributes()
            intersections = index.intersects(geom.boundingBox())

            request = QgsFeatureRequest().setFilterFids(intersections).setSubsetOfAttributes([])
            for inFeatB in layerB.getFeatures(request):
                tmpGeom = inFeatB.geometry()
                if diff_geom.intersects(tmpGeom):
                    diff_geom = QgsGeometry(diff_geom.difference(tmpGeom))

            try:
                outFeat.setGeometry(diff_geom)
                outFeat.setAttributes(attrs)
                writer.addFeature(outFeat, QgsFeatureSink.FastInsert)
            except:
                QgsMessageLog.logMessage(self.tr('Feature geometry error: One or more output features ignored due to invalid geometry.'), self.tr('Processing'), QgsMessageLog.WARNING)
                continue

            feedback.setProgress(int(current * total))

        del writer