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This algorithm allows you to extract specific nodes from geometries. Eg you can extract the first or last node in the geometry. The algorithm accepts a comma separated list of node indices to extract, eg 0 = first node, 1 = second node, etc. Negative indices can be used to extract nodes from the end of the geometry. Eg -1 = last node, -2 = second last node.
119 lines
4.5 KiB
Python
119 lines
4.5 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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ExtractSpecificNodes.py
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--------------------
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Date : October 2016
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Copyright : (C) 2016 by Nyall Dawson
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Email : nyall dot dawson at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Nyall Dawson'
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__date__ = 'October 2016'
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__copyright__ = '(C) 2016, Nyall Dawson'
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# This will get replaced with a git SHA1 when you do a git archive323
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__revision__ = '$Format:%H$'
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import math
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.core.parameters import ParameterVector, ParameterString
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from processing.core.outputs import OutputVector
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from processing.tools import dataobjects, vector
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from qgis.core import QgsWkbTypes, QgsFeature, QgsGeometry, QgsField
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from qgis.PyQt.QtCore import QVariant
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class ExtractSpecificNodes(GeoAlgorithm):
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INPUT_LAYER = 'INPUT_LAYER'
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OUTPUT_LAYER = 'OUTPUT_LAYER'
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NODES = 'NODES'
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def defineCharacteristics(self):
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self.name, self.i18n_name = self.trAlgorithm('Extract specific nodes')
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self.group, self.i18n_group = self.trAlgorithm('Vector geometry tools')
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self.addParameter(ParameterVector(self.INPUT_LAYER,
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self.tr('Input layer'), [dataobjects.TYPE_VECTOR_ANY]))
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self.addParameter(ParameterString(self.NODES,
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self.tr('Node indices'), default='0'))
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self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Nodes'), datatype=[dataobjects.TYPE_VECTOR_POINT]))
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def processAlgorithm(self, progress):
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layer = dataobjects.getObjectFromUri(
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self.getParameterValue(self.INPUT_LAYER))
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fields = layer.fields()
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fields.append(QgsField('node_pos', QVariant.Int))
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fields.append(QgsField('node_index', QVariant.Int))
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fields.append(QgsField('distance', QVariant.Double))
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fields.append(QgsField('angle', QVariant.Double))
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writer = self.getOutputFromName(
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self.OUTPUT_LAYER).getVectorWriter(
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fields,
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QgsWkbTypes.Point,
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layer.crs())
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node_indices_string = self.getParameterValue(self.NODES)
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indices = []
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for node in node_indices_string.split(','):
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try:
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indices.append(int(node))
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except:
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raise GeoAlgorithmExecutionException(
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self.tr('\'{}\' is not a valid node index').format(node))
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features = vector.features(layer)
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total = 100.0 / len(features)
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for current, f in enumerate(features):
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input_geometry = f.geometry()
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if not input_geometry:
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writer.addFeature(f)
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else:
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total_nodes = input_geometry.geometry().nCoordinates()
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for node in indices:
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if node < 0:
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node_index = total_nodes + node
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else:
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node_index = node
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if node_index < 0 or node_index >= total_nodes:
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continue
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distance = input_geometry.distanceToVertex(node_index)
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angle = math.degrees(input_geometry.angleAtVertex(node_index))
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output_feature = QgsFeature()
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attrs = f.attributes()
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attrs.append(node)
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attrs.append(node_index)
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attrs.append(distance)
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attrs.append(angle)
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output_feature.setAttributes(attrs)
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point = input_geometry.vertexAt(node_index)
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output_feature.setGeometry(QgsGeometry.fromPoint(point))
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writer.addFeature(output_feature)
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progress.setPercentage(int(current * total))
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del writer
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