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

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

"""
***************************************************************************
    OffsetLine.py
    --------------
    Date                 : July 2016
    Copyright            : (C) 2016 by Nyall Dawson
    Email                : nyall dot dawson 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__ = 'Nyall Dawson'
__date__ = 'July 2016'
__copyright__ = '(C) 2016, Nyall Dawson'

# This will get replaced with a git SHA1 when you do a git archive323

__revision__ = '$Format:%H$'

import os

from qgis.core import QgsWkbTypes

from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterVector, ParameterSelection, ParameterNumber
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 OffsetLine(GeoAlgorithm):

    INPUT_LAYER = 'INPUT_LAYER'
    OUTPUT_LAYER = 'OUTPUT_LAYER'
    DISTANCE = 'DISTANCE'
    SEGMENTS = 'SEGMENTS'
    JOIN_STYLE = 'JOIN_STYLE'
    MITRE_LIMIT = 'MITRE_LIMIT'

    def defineCharacteristics(self):
        self.name, self.i18n_name = self.trAlgorithm('Offset line')
        self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')

        self.addParameter(ParameterVector(self.INPUT_LAYER,
                                          self.tr('Input layer'), [dataobjects.TYPE_VECTOR_LINE]))
        self.addParameter(ParameterNumber(self.DISTANCE,
                                          self.tr('Distance'), default=10.0))
        self.addParameter(ParameterNumber(self.SEGMENTS,
                                          self.tr('Segments'), 1, default=8))
        self.join_styles = [self.tr('Round'),
                            'Mitre',
                            'Bevel']
        self.addParameter(ParameterSelection(
            self.JOIN_STYLE,
            self.tr('Join style'),
            self.join_styles))
        self.addParameter(ParameterNumber(self.MITRE_LIMIT,
                                          self.tr('Mitre limit'), 1, default=2))

        self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Offset'), datatype=[dataobjects.TYPE_VECTOR_LINE]))

    def processAlgorithm(self, feedback):
        layer = dataobjects.getObjectFromUri(
            self.getParameterValue(self.INPUT_LAYER))

        writer = self.getOutputFromName(
            self.OUTPUT_LAYER).getVectorWriter(
                layer.fields().toList(),
                QgsWkbTypes.LineString,
                layer.crs())

        distance = self.getParameterValue(self.DISTANCE)
        segments = int(self.getParameterValue(self.SEGMENTS))
        join_style = self.getParameterValue(self.JOIN_STYLE) + 1
        miter_limit = self.getParameterValue(self.MITRE_LIMIT)

        features = vector.features(layer)
        total = 100.0 / len(features)

        for current, input_feature in enumerate(features):
            output_feature = input_feature
            input_geometry = input_feature.geometry()
            if input_geometry:
                output_geometry = input_geometry.offsetCurve(distance, segments, join_style, miter_limit)
                if not output_geometry:
                    raise GeoAlgorithmExecutionException(
                        self.tr('Error calculating line offset'))

                output_feature.setGeometry(output_geometry)

            writer.addFeature(output_feature)
            feedback.setProgress(int(current * total))

        del writer