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 Qgis, QgsFeature, QgsGeometry

from processing.core.GeoAlgorithm import GeoAlgorithm
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 PolygonsToLines(GeoAlgorithm):

    INPUT = 'INPUT'
    OUTPUT = 'OUTPUT'

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

    def defineCharacteristics(self):
        self.name, self.i18n_name = self.trAlgorithm('Polygons to lines')
        self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')

        self.addParameter(ParameterVector(self.INPUT,
                                          self.tr('Input layer'), [ParameterVector.VECTOR_TYPE_POLYGON]))

        self.addOutput(OutputVector(self.OUTPUT, self.tr('Lines from polygons')))

    def processAlgorithm(self, progress):
        layer = dataobjects.getObjectFromUri(self.getParameterValue(self.INPUT))

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(
            layer.pendingFields().toList(), Qgis.WKBLineString, layer.crs())

        outFeat = QgsFeature()
        inGeom = QgsGeometry()
        outGeom = QgsGeometry()

        features = vector.features(layer)
        total = 100.0 / len(features)
        for current, f in enumerate(features):
            inGeom = f.geometry()
            attrs = f.attributes()
            lineList = self.extractAsLine(inGeom)
            outFeat.setAttributes(attrs)
            for h in lineList:
                outFeat.setGeometry(outGeom.fromPolyline(h))
                writer.addFeature(outFeat)

            progress.setPercentage(int(current * total))

        del writer

    def extractAsLine(self, geom):
        multiGeom = QgsGeometry()
        lines = []
        if geom and geom.type() == Qgis.Polygon:
            if geom.isMultipart():
                multiGeom = geom.asMultiPolygon()
                for i in multiGeom:
                    lines.extend(i)
            else:
                multiGeom = geom.asPolygon()
                lines = multiGeom
            return lines
        else:
            return []