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

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

"""
***************************************************************************
    PolygonsToLines.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 QgsGeometry, QgsWkbTypes, QgsFeatureSink, QgsProcessingUtils

from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
from processing.core.parameters import ParameterVector
from processing.core.outputs import OutputVector
from processing.tools import dataobjects

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


class PolygonsToLines(QgisAlgorithm):

    INPUT = 'INPUT'
    OUTPUT = 'OUTPUT'

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

    def tags(self):
        return self.tr('line,polygon,convert').split(',')

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

    def __init__(self):
        super().__init__()
        self.addParameter(ParameterVector(self.INPUT,
                                          self.tr('Input layer'), [dataobjects.TYPE_VECTOR_POLYGON]))

        self.addOutput(OutputVector(self.OUTPUT, self.tr('Lines from polygons'), datatype=[dataobjects.TYPE_VECTOR_LINE]))

    def name(self):
        return 'polygonstolines'

    def displayName(self):
        return self.tr('Polygons to lines')

    def processAlgorithm(self, parameters, context, feedback):
        layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(layer.fields(), QgsWkbTypes.LineString,
                                                                     layer.crs(), context)

        features = QgsProcessingUtils.getFeatures(layer, context)
        total = 100.0 / layer.featureCount() if layer.featureCount() else 0
        for current, f in enumerate(features):
            if f.hasGeometry():
                lines = QgsGeometry(f.geometry().geometry().boundary()).asGeometryCollection()
                for line in lines:
                    f.setGeometry(line)
                    writer.addFeature(f, QgsFeatureSink.FastInsert)
            else:
                writer.addFeature(f, QgsFeatureSink.FastInsert)

            feedback.setProgress(int(current * total))

        del writer