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

"""
***************************************************************************
    RandomPointsAlongLines.py
    ---------------------
    Date                 : April 2014
    Copyright            : (C) 2014 by Alexander Bruy
    Email                : alexander dot bruy 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__ = "Alexander Bruy"
__date__ = "April 2014"
__copyright__ = "(C) 2014, Alexander Bruy"

import random

from qgis.PyQt.QtCore import QMetaType
from qgis.core import (
    Qgis,
    QgsField,
    QgsFeatureSink,
    QgsFeature,
    QgsFields,
    QgsGeometry,
    QgsPointXY,
    QgsWkbTypes,
    QgsSpatialIndex,
    QgsFeatureRequest,
    QgsDistanceArea,
    QgsProject,
    QgsProcessing,
    QgsProcessingException,
    QgsProcessingParameterDistance,
    QgsProcessingParameterNumber,
    QgsProcessingParameterFeatureSource,
    QgsProcessingParameterFeatureSink,
    QgsProcessingParameterDefinition,
)

from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
from processing.tools import vector


class RandomPointsAlongLines(QgisAlgorithm):
    INPUT = "INPUT"
    POINTS_NUMBER = "POINTS_NUMBER"
    MIN_DISTANCE = "MIN_DISTANCE"
    OUTPUT = "OUTPUT"

    def group(self):
        return self.tr("Vector creation")

    def groupId(self):
        return "vectorcreation"

    def __init__(self):
        super().__init__()

    def initAlgorithm(self, config=None):
        self.addParameter(
            QgsProcessingParameterFeatureSource(
                self.INPUT,
                self.tr("Input layer"),
                [QgsProcessing.SourceType.TypeVectorLine],
            )
        )
        self.addParameter(
            QgsProcessingParameterNumber(
                self.POINTS_NUMBER,
                self.tr("Number of points"),
                QgsProcessingParameterNumber.Type.Integer,
                1,
                False,
                1,
                1000000000,
            )
        )
        self.addParameter(
            QgsProcessingParameterDistance(
                self.MIN_DISTANCE,
                self.tr("Minimum distance between points"),
                0,
                self.INPUT,
                False,
                0,
                1000000000,
            )
        )
        self.addParameter(
            QgsProcessingParameterFeatureSink(
                self.OUTPUT,
                self.tr("Random points"),
                type=QgsProcessing.SourceType.TypeVectorPoint,
            )
        )

    def name(self):
        return "randompointsalongline"

    def displayName(self):
        return self.tr("Random points along line")

    def documentationFlags(self):
        return Qgis.ProcessingAlgorithmDocumentationFlag.RegeneratesPrimaryKey

    def processAlgorithm(self, parameters, context, feedback):
        source = self.parameterAsSource(parameters, self.INPUT, context)
        if source is None:
            raise QgsProcessingException(
                self.invalidSourceError(parameters, self.INPUT)
            )

        pointCount = self.parameterAsDouble(parameters, self.POINTS_NUMBER, context)
        minDistance = self.parameterAsDouble(parameters, self.MIN_DISTANCE, context)

        fields = QgsFields()
        fields.append(QgsField("id", QMetaType.Type.Int, "", 10, 0))

        (sink, dest_id) = self.parameterAsSink(
            parameters,
            self.OUTPUT,
            context,
            fields,
            QgsWkbTypes.Type.Point,
            source.sourceCrs(),
            QgsFeatureSink.SinkFlag.RegeneratePrimaryKey,
        )
        if sink is None:
            raise QgsProcessingException(self.invalidSinkError(parameters, self.OUTPUT))

        nPoints = 0
        nIterations = 0
        maxIterations = pointCount * 200
        total = 100.0 / pointCount if pointCount else 1

        index = QgsSpatialIndex()
        points = {}

        da = QgsDistanceArea()
        da.setSourceCrs(source.sourceCrs(), context.transformContext())
        da.setEllipsoid(context.ellipsoid())

        request = QgsFeatureRequest()

        random.seed()

        ids = source.allFeatureIds()

        while ids and nIterations < maxIterations and nPoints < pointCount:
            if feedback.isCanceled():
                break

            # pick random feature
            fid = random.choice(ids)
            try:
                f = next(
                    source.getFeatures(
                        request.setFilterFid(fid).setSubsetOfAttributes([])
                    )
                )
            except StopIteration:
                ids.remove(fid)
                continue

            fGeom = f.geometry()
            if fGeom.isEmpty():
                ids.remove(fid)
                continue

            if fGeom.isMultipart():
                lines = fGeom.asMultiPolyline()
                # pick random line
                lineId = random.randint(0, len(lines) - 1)
                vertices = lines[lineId]
            else:
                vertices = fGeom.asPolyline()

            # pick random segment
            nVertices = len(vertices)
            if nVertices < 2:
                nIterations += 1
                continue
            if nVertices == 2:
                vid = 0
            else:
                vid = random.randint(0, nVertices - 2)
            startPoint = vertices[vid]
            endPoint = vertices[vid + 1]
            length = da.measureLine(startPoint, endPoint)
            if length == 0:
                nIterations += 1
                continue
            dist = length * random.random()

            d = dist / (length - dist)
            rx = (startPoint.x() + d * endPoint.x()) / (1 + d)
            ry = (startPoint.y() + d * endPoint.y()) / (1 + d)

            # generate random point
            p = QgsPointXY(rx, ry)
            geom = QgsGeometry.fromPointXY(p)
            if vector.checkMinDistance(p, index, minDistance, points):
                f = QgsFeature(nPoints)
                f.initAttributes(1)
                f.setFields(fields)
                f.setAttribute("id", nPoints)
                f.setGeometry(geom)
                sink.addFeature(f, QgsFeatureSink.Flag.FastInsert)
                index.addFeature(f)
                points[nPoints] = p
                nPoints += 1
                feedback.setProgress(int(nPoints * total))
            nIterations += 1

        if nPoints < pointCount:
            feedback.pushInfo(
                self.tr(
                    "Could not generate requested number of random points. "
                    "Maximum number of attempts exceeded."
                )
            )

        sink.finalize()
        return {self.OUTPUT: dest_id}