QGIS/python/plugins/processing/algs/qgis/Clip.py

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

"""
***************************************************************************
    Clip.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 Qgis, QgsFeature, QgsGeometry, QgsFeatureRequest, QgsWkbTypes, QgsWkbTypes

from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.ProcessingLog import ProcessingLog
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterVector
from processing.core.outputs import OutputVector
from processing.tools import dataobjects, vector

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


class Clip(GeoAlgorithm):

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

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

    def defineCharacteristics(self):
        self.name, self.i18n_name = self.trAlgorithm('Clip')
        self.group, self.i18n_group = self.trAlgorithm('Vector overlay tools')
        self.addParameter(ParameterVector(Clip.INPUT,
                                          self.tr('Input layer')))
        self.addParameter(ParameterVector(Clip.OVERLAY,
                                          self.tr('Clip layer'), [dataobjects.TYPE_VECTOR_POLYGON]))
        self.addOutput(OutputVector(Clip.OUTPUT, self.tr('Clipped')))

    def processAlgorithm(self, progress):
        source_layer = dataobjects.getObjectFromUri(
            self.getParameterValue(Clip.INPUT))
        mask_layer = dataobjects.getObjectFromUri(
            self.getParameterValue(Clip.OVERLAY))

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
            source_layer.fields(),
            QgsWkbTypes.multiType(source_layer.wkbType()),
            source_layer.crs())

        # first build up a list of clip geometries
        clip_geoms = []
        for maskFeat in vector.features(mask_layer, QgsFeatureRequest().setSubsetOfAttributes([])):
            clip_geoms.append(maskFeat.geometry())

        # are we clipping against a single feature? if so, we can show finer progress reports
        if len(clip_geoms) > 1:
            combined_clip_geom = QgsGeometry.unaryUnion(clip_geoms)
            single_clip_feature = False
        else:
            combined_clip_geom = clip_geoms[0]
            single_clip_feature = True

        # use prepared geometries for faster intersection tests
        engine = QgsGeometry.createGeometryEngine(combined_clip_geom.geometry())
        engine.prepareGeometry()

        tested_feature_ids = set()

        for i, clip_geom in enumerate(clip_geoms):
            input_features = [f for f in vector.features(source_layer, QgsFeatureRequest().setFilterRect(clip_geom.boundingBox()))]

            if not input_features:
                continue

            if single_clip_feature:
                total = 100.0 / len(input_features)
            else:
                total = 0

            for current, in_feat in enumerate(input_features):
                if not in_feat.geometry():
                    continue

                if in_feat.id() in tested_feature_ids:
                    # don't retest a feature we have already checked
                    continue

                tested_feature_ids.add(in_feat.id())

                if not engine.intersects(in_feat.geometry().geometry()):
                    continue

                if not engine.contains(in_feat.geometry().geometry()):
                    cur_geom = in_feat.geometry()
                    new_geom = combined_clip_geom.intersection(cur_geom)
                    if new_geom.wkbType() == QgsWkbTypes.Unknown or QgsWkbTypes.flatType(new_geom.geometry().wkbType()) == QgsWkbTypes.GeometryCollection:
                        int_com = in_feat.geometry().combine(new_geom)
                        int_sym = in_feat.geometry().symDifference(new_geom)
                        if not int_com or not int_sym:
                            ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
                                                   self.tr('GEOS geoprocessing error: One or more '
                                                           'input features have invalid geometry.'))
                        else:
                            new_geom = int_com.difference(int_sym)
                            if new_geom.isGeosEmpty() or not new_geom.isGeosValid():
                                ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
                                                       self.tr('GEOS geoprocessing error: One or more '
                                                               'input features have invalid geometry.'))
                else:
                    # clip geometry totally contains feature geometry, so no need to perform intersection
                    new_geom = in_feat.geometry()

                try:
                    out_feat = QgsFeature()
                    out_feat.setGeometry(new_geom)
                    out_feat.setAttributes(in_feat.attributes())
                    writer.addFeature(out_feat)
                except:
                    ProcessingLog.addToLog(ProcessingLog.LOG_ERROR,
                                           self.tr('Feature geometry error: One or more '
                                                   'output features ignored due to '
                                                   'invalid geometry.'))
                    continue

                if single_clip_feature:
                    progress.setPercentage(int(current * total))

            if not single_clip_feature:
                # coarse progress report for multiple clip geometries
                progress.setPercentage(100.0 * i / len(clip_geoms))

        del writer