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

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

"""
***************************************************************************
    ExtractSpecificNodes.py
    --------------------
    Date                 : October 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__ = 'October 2016'
__copyright__ = '(C) 2016, Nyall Dawson'

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

__revision__ = '$Format:%H$'

import math
from processing.algs.qgis import QgisAlgorithm
from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
from processing.core.parameters import ParameterVector, ParameterString
from processing.core.outputs import OutputVector
from processing.tools import dataobjects

from qgis.core import (QgsWkbTypes,
                       QgsFeature,
                       QgsGeometry,
                       QgsField,
                       QgsApplication,
                       QgsProcessingUtils)
from qgis.PyQt.QtCore import QVariant


class ExtractSpecificNodes(QgisAlgorithm):

    INPUT_LAYER = 'INPUT_LAYER'
    OUTPUT_LAYER = 'OUTPUT_LAYER'
    NODES = 'NODES'

    def icon(self):
        return QgsApplication.getThemeIcon("/providerQgis.svg")

    def svgIconPath(self):
        return QgsApplication.iconPath("providerQgis.svg")

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

    def __init__(self):
        super().__init__()
        self.addParameter(ParameterVector(self.INPUT_LAYER,
                                          self.tr('Input layer'), [dataobjects.TYPE_VECTOR_ANY]))
        self.addParameter(ParameterString(self.NODES,
                                          self.tr('Node indices'), default='0'))
        self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Nodes'), datatype=[dataobjects.TYPE_VECTOR_POINT]))

    def name(self):
        return 'extractspecificnodes'

    def displayName(self):
        return self.tr('Extract specific nodes')

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

        fields = layer.fields()
        fields.append(QgsField('node_pos', QVariant.Int))
        fields.append(QgsField('node_index', QVariant.Int))
        fields.append(QgsField('distance', QVariant.Double))
        fields.append(QgsField('angle', QVariant.Double))

        writer = self.getOutputFromName(
            self.OUTPUT_LAYER).getVectorWriter(fields, QgsWkbTypes.Point, layer.crs(), context)

        node_indices_string = self.getParameterValue(self.NODES)
        indices = []
        for node in node_indices_string.split(','):
            try:
                indices.append(int(node))
            except:
                raise GeoAlgorithmExecutionException(
                    self.tr('\'{}\' is not a valid node index').format(node))

        features = QgsProcessingUtils.getFeatures(layer, context)
        total = 100.0 / QgsProcessingUtils.featureCount(layer, context)

        for current, f in enumerate(features):

            input_geometry = f.geometry()
            if not input_geometry:
                writer.addFeature(f)
            else:
                total_nodes = input_geometry.geometry().nCoordinates()

                for node in indices:
                    if node < 0:
                        node_index = total_nodes + node
                    else:
                        node_index = node

                    if node_index < 0 or node_index >= total_nodes:
                        continue

                    distance = input_geometry.distanceToVertex(node_index)
                    angle = math.degrees(input_geometry.angleAtVertex(node_index))

                    output_feature = QgsFeature()
                    attrs = f.attributes()
                    attrs.append(node)
                    attrs.append(node_index)
                    attrs.append(distance)
                    attrs.append(angle)
                    output_feature.setAttributes(attrs)

                    point = input_geometry.vertexAt(node_index)
                    output_feature.setGeometry(QgsGeometry.fromPoint(point))

                    writer.addFeature(output_feature)

            feedback.setProgress(int(current * total))

        del writer