Python QgsDistanceArea.setSourceCrs方法代码示例

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def testRenderMetersInMapUnits(self):

        crs_wsg84 = QgsCoordinateReferenceSystem.fromOgcWmsCrs('EPSG:4326')
        rt_extent = QgsRectangle(13.37768985634235, 52.51625705830762, 13.37771931686235, 52.51628651882762)
        point_berlin_wsg84 = QgsPointXY(13.37770458660236, 52.51627178856762)
        length_wsg84_mapunits = 0.00001473026350140572
        meters_test = 2.40
        da_wsg84 = QgsDistanceArea()
        da_wsg84.setSourceCrs(crs_wsg84, QgsProject.instance().transformContext())
        if (da_wsg84.sourceCrs().isGeographic()):
            da_wsg84.setEllipsoid(da_wsg84.sourceCrs().ellipsoidAcronym())
        length_meter_mapunits = da_wsg84.measureLineProjected(point_berlin_wsg84, 1.0, (math.pi / 2))
        meters_test_mapunits = meters_test * length_wsg84_mapunits
        meters_test_pixel = meters_test * length_wsg84_mapunits
        ms = QgsMapSettings()
        ms.setDestinationCrs(crs_wsg84)
        ms.setExtent(rt_extent)
        r = QgsRenderContext.fromMapSettings(ms)
        r.setExtent(rt_extent)
        self.assertEqual(r.extent().center().toString(7), point_berlin_wsg84.toString(7))
        c = QgsMapUnitScale()
        r.setDistanceArea(da_wsg84)
        result_test_painterunits = r.convertToPainterUnits(meters_test, QgsUnitTypes.RenderMetersInMapUnits, c)
        self.assertEqual(QgsDistanceArea.formatDistance(result_test_painterunits, 7, QgsUnitTypes.DistanceUnknownUnit, True), QgsDistanceArea.formatDistance(meters_test_mapunits, 7, QgsUnitTypes.DistanceUnknownUnit, True))
        result_test_mapunits = r.convertToMapUnits(meters_test, QgsUnitTypes.RenderMetersInMapUnits, c)
        self.assertEqual(QgsDistanceArea.formatDistance(result_test_mapunits, 7, QgsUnitTypes.DistanceDegrees, True), QgsDistanceArea.formatDistance(meters_test_mapunits, 7, QgsUnitTypes.DistanceDegrees, True))
        result_test_meters = r.convertFromMapUnits(meters_test_mapunits, QgsUnitTypes.RenderMetersInMapUnits)
        self.assertEqual(QgsDistanceArea.formatDistance(result_test_meters, 1, QgsUnitTypes.DistanceMeters, True), QgsDistanceArea.formatDistance(meters_test, 1, QgsUnitTypes.DistanceMeters, True))

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
def simpleMeasure(geom, method=0, ellips=None, crs=None):
    # Method defines calculation type:
    # 0 - layer CRS
    # 1 - project CRS
    # 2 - ellipsoidal

    if geom.wkbType() in [QGis.WKBPoint, QGis.WKBPoint25D]:
        pt = geom.asPoint()
        attr1 = pt.x()
        attr2 = pt.y()
    elif geom.wkbType() in [QGis.WKBMultiPoint, QGis.WKBMultiPoint25D]:
        pt = geom.asMultiPoint()
        attr1 = pt[0].x()
        attr2 = pt[0].y()
    else:
        measure = QgsDistanceArea()

        if method == 2:
            measure.setSourceCrs(crs)
            measure.setEllipsoid(ellips)
            measure.setEllipsoidalMode(True)

        attr1 = measure.measure(geom)
        if geom.type() == QGis.Polygon:
            attr2 = measure.measurePerimeter(geom)
        else:
            attr2 = None

    return (attr1, attr2)

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def processAlgorithm(self, parameters, context, feedback):
        if parameters[self.INPUT] == parameters[self.HUBS]:
            raise QgsProcessingException(
                self.tr('Same layer given for both hubs and spokes'))

        point_source = self.parameterAsSource(parameters, self.INPUT, context)
        hub_source = self.parameterAsSource(parameters, self.HUBS, context)
        fieldName = self.parameterAsString(parameters, self.FIELD, context)

        units = self.UNITS[self.parameterAsEnum(parameters, self.UNIT, context)]

        fields = point_source.fields()
        fields.append(QgsField('HubName', QVariant.String))
        fields.append(QgsField('HubDist', QVariant.Double))

        (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
                                               fields, QgsWkbTypes.Point, point_source.sourceCrs())

        index = QgsSpatialIndex(hub_source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([]).setDestinationCrs(point_source.sourceCrs(), context.transformContext())))

        distance = QgsDistanceArea()
        distance.setSourceCrs(point_source.sourceCrs(), context.transformContext())
        distance.setEllipsoid(context.project().ellipsoid())

        # Scan source points, find nearest hub, and write to output file
        features = point_source.getFeatures()
        total = 100.0 / point_source.featureCount() if point_source.featureCount() else 0
        for current, f in enumerate(features):
            if feedback.isCanceled():
                break

            if not f.hasGeometry():
                sink.addFeature(f, QgsFeatureSink.FastInsert)
                continue

            src = f.geometry().boundingBox().center()

            neighbors = index.nearestNeighbor(src, 1)
            ft = next(hub_source.getFeatures(QgsFeatureRequest().setFilterFid(neighbors[0]).setSubsetOfAttributes([fieldName], hub_source.fields()).setDestinationCrs(point_source.sourceCrs(), context.transformContext())))
            closest = ft.geometry().boundingBox().center()
            hubDist = distance.measureLine(src, closest)

            if units != self.LAYER_UNITS:
                hub_dist_in_desired_units = distance.convertLengthMeasurement(hubDist, units)
            else:
                hub_dist_in_desired_units = hubDist

            attributes = f.attributes()
            attributes.append(ft[fieldName])
            attributes.append(hub_dist_in_desired_units)

            feat = QgsFeature()
            feat.setAttributes(attributes)

            feat.setGeometry(QgsGeometry.fromPointXY(src))

            sink.addFeature(feat, QgsFeatureSink.FastInsert)
            feedback.setProgress(int(current * total))

        return {self.OUTPUT: dest_id}

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def prepareAlgorithm(self, parameters, context, feedback):
        source = self.parameterAsSource(parameters, 'INPUT', context)
        mapping = self.parameterAsFieldsMapping(parameters, self.FIELDS_MAPPING, context)

        self.fields = QgsFields()
        self.expressions = []

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

        # create an expression context using thread safe processing context
        self.expr_context = self.createExpressionContext(parameters, context, source)

        for field_def in mapping:
            self.fields.append(QgsField(name=field_def['name'],
                                        type=field_def['type'],
                                        typeName="",
                                        len=field_def.get('length', 0),
                                        prec=field_def.get('precision', 0)))
            expression = QgsExpression(field_def['expression'])
            expression.setGeomCalculator(da)
            expression.setDistanceUnits(context.project().distanceUnits())
            expression.setAreaUnits(context.project().areaUnits())
            if expression.hasParserError():
                raise QgsProcessingException(
                    self.tr(u'Parser error in expression "{}": {}')
                    .format(str(expression.expression()),
                            str(expression.parserErrorString())))
            self.expressions.append(expression)
        return True

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def _calc_north(self):
        extent = self.canvas.extent()
        if self.canvas.layerCount() == 0 or extent.isEmpty():
            print "No layers or extent"
            return 0

        outcrs = self.canvas.mapSettings().destinationCrs()

        if outcrs.isValid() and not outcrs.geographicFlag():
            crs = QgsCoordinateReferenceSystem()
            crs.createFromOgcWmsCrs("EPSG:4326")

            transform = QgsCoordinateTransform(outcrs, crs)

            p1 = QgsPoint(extent.center())
            p2 = QgsPoint(p1.x(), p1.y() + extent.height() * 0.25)

            try:
                pp1 = transform.transform(p1)
                pp2 = transform.transform(p2)
            except QgsCsException:
                roam.utils.warning("North arrow. Error transforming.")
                return None

            area = QgsDistanceArea()
            area.setEllipsoid(crs.ellipsoidAcronym())
            area.setEllipsoidalMode(True)
            area.setSourceCrs(crs)
            distance, angle, _ = area.computeDistanceBearing(pp1, pp2)
            angle = math.degrees(angle)
            return angle
        else:
            return 0

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def processAlgorithm(self, parameters, context, feedback):
        layerPoints = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.POINTS), context)
        layerHubs = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.HUBS), context)
        fieldName = self.getParameterValue(self.FIELD)

        units = self.UNITS[self.getParameterValue(self.UNIT)]

        if layerPoints.source() == layerHubs.source():
            raise GeoAlgorithmExecutionException(
                self.tr('Same layer given for both hubs and spokes'))

        fields = layerPoints.fields()
        fields.append(QgsField('HubName', QVariant.String))
        fields.append(QgsField('HubDist', QVariant.Double))

        writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(fields, QgsWkbTypes.LineString, layerPoints.crs(),
                                                                     context)

        index = QgsProcessingUtils.createSpatialIndex(layerHubs, context)

        distance = QgsDistanceArea()
        distance.setSourceCrs(layerPoints.crs())
        distance.setEllipsoid(QgsProject.instance().ellipsoid())

        # Scan source points, find nearest hub, and write to output file
        features = QgsProcessingUtils.getFeatures(layerPoints, context)
        total = 100.0 / layerPoints.featureCount() if layerPoints.featureCount() else 0
        for current, f in enumerate(features):
            src = f.geometry().boundingBox().center()

            neighbors = index.nearestNeighbor(src, 1)
            ft = next(layerHubs.getFeatures(QgsFeatureRequest().setFilterFid(neighbors[0]).setSubsetOfAttributes([fieldName], layerHubs.fields())))
            closest = ft.geometry().boundingBox().center()
            hubDist = distance.measureLine(src, closest)

            attributes = f.attributes()
            attributes.append(ft[fieldName])
            if units == 'Feet':
                attributes.append(hubDist * 3.2808399)
            elif units == 'Miles':
                attributes.append(hubDist * 0.000621371192)
            elif units == 'Kilometers':
                attributes.append(hubDist / 1000.0)
            elif units != 'Meters':
                attributes.append(sqrt(
                    pow(src.x() - closest.x(), 2.0) +
                    pow(src.y() - closest.y(), 2.0)))
            else:
                attributes.append(hubDist)

            feat = QgsFeature()
            feat.setAttributes(attributes)

            feat.setGeometry(QgsGeometry.fromPolyline([src, closest]))

            writer.addFeature(feat, QgsFeatureSink.FastInsert)
            feedback.setProgress(int(current * total))

        del writer

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def processAlgorithm(self, parameters, context, feedback):
        source = self.parameterAsSource(parameters, self.INPUT, context)
        layer = self.parameterAsVectorLayer(parameters, self.INPUT, context)
        field_name = self.parameterAsString(parameters, self.FIELD_NAME, context)
        field_type = self.TYPES[self.parameterAsEnum(parameters, self.FIELD_TYPE, context)]
        width = self.parameterAsInt(parameters, self.FIELD_LENGTH, context)
        precision = self.parameterAsInt(parameters, self.FIELD_PRECISION, context)
        new_field = self.parameterAsBool(parameters, self.NEW_FIELD, context)
        formula = self.parameterAsString(parameters, self.FORMULA, context)

        expression = QgsExpression(formula)
        da = QgsDistanceArea()
        da.setSourceCrs(source.sourceCrs())
        da.setEllipsoid(context.project().ellipsoid())
        expression.setGeomCalculator(da)

        expression.setDistanceUnits(context.project().distanceUnits())
        expression.setAreaUnits(context.project().areaUnits())

        fields = source.fields()
        field_index = fields.lookupField(field_name)
        if new_field or field_index < 0:
            fields.append(QgsField(field_name, field_type, '', width, precision))

        (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
                                               fields, source.wkbType(), source.sourceCrs())

        exp_context = self.createExpressionContext(parameters, context)
        if layer is not None:
            exp_context.appendScope(QgsExpressionContextUtils.layerScope(layer))

        if not expression.prepare(exp_context):
            raise QgsProcessingException(
                self.tr('Evaluation error: {0}').format(expression.parserErrorString()))

        features = source.getFeatures()
        total = 100.0 / source.featureCount() if source.featureCount() else 0

        for current, f in enumerate(features):
            if feedback.isCanceled():
                break

            rownum = current + 1
            exp_context.setFeature(f)
            exp_context.lastScope().setVariable("row_number", rownum)
            value = expression.evaluate(exp_context)
            if expression.hasEvalError():
                feedback.reportError(expression.evalErrorString())
            else:
                attrs = f.attributes()
                if new_field or field_index < 0:
                    attrs.append(value)
                else:
                    attrs[field_index] = value
                f.setAttributes(attrs)
                sink.addFeature(f, QgsFeatureSink.FastInsert)
            feedback.setProgress(int(current * total))

        return {self.OUTPUT: dest_id}

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def testCrs(self):
        # test setting/getting the source CRS
        da = QgsDistanceArea()

        # try setting using a CRS object
        crs = QgsCoordinateReferenceSystem(3111, QgsCoordinateReferenceSystem.EpsgCrsId)
        da.setSourceCrs(crs, QgsProject.instance().transformContext())
        self.assertEqual(da.sourceCrs().srsid(), crs.srsid())

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
	def calculateDistance(self, p1, p2):
		distance = QgsDistanceArea()
		distance.setSourceCrs(self.iface.activeLayer().crs())
		distance.setEllipsoidalMode(True)
		# Sirgas 2000
		distance.setEllipsoid('GRS1980')
		m = distance.measureLine(p1, p2) 
		return m

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def processAlgorithm(self, parameters, context, feedback):
        source = self.parameterAsSource(parameters, self.INPUT, context)
        if source is None:
            raise QgsProcessingException(self.invalidSourceError(parameters, self.INPUT))

        output_file = self.parameterAsFileOutput(parameters, self.OUTPUT_HTML_FILE, context)

        spatialIndex = QgsSpatialIndex(source, feedback)

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

        sumDist = 0.00
        A = source.sourceExtent()
        A = float(A.width() * A.height())

        features = source.getFeatures()
        count = source.featureCount()
        total = 100.0 / count if count else 1
        for current, feat in enumerate(features):
            if feedback.isCanceled():
                break

            neighbourID = spatialIndex.nearestNeighbor(
                feat.geometry().asPoint(), 2)[1]
            request = QgsFeatureRequest().setFilterFid(neighbourID).setSubsetOfAttributes([])
            neighbour = next(source.getFeatures(request))
            sumDist += distance.measureLine(neighbour.geometry().asPoint(),
                                            feat.geometry().asPoint())

            feedback.setProgress(int(current * total))

        do = float(sumDist) / count
        de = float(0.5 / math.sqrt(count / A))
        d = float(do / de)
        SE = float(0.26136 / math.sqrt(count ** 2 / A))
        zscore = float((do - de) / SE)

        results = {}
        results[self.OBSERVED_MD] = do
        results[self.EXPECTED_MD] = de
        results[self.NN_INDEX] = d
        results[self.POINT_COUNT] = count
        results[self.Z_SCORE] = zscore

        if output_file:
            data = []
            data.append('Observed mean distance: ' + str(do))
            data.append('Expected mean distance: ' + str(de))
            data.append('Nearest neighbour index: ' + str(d))
            data.append('Number of points: ' + str(count))
            data.append('Z-Score: ' + str(zscore))
            self.createHTML(output_file, data)
            results[self.OUTPUT_HTML_FILE] = output_file

        return results

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def testLengthMeasureAndUnits(self):
        """Test a variety of length measurements in different CRS and ellipsoid modes, to check that the
           calculated lengths and units are always consistent
        """

        da = QgsDistanceArea()
        da.setSourceCrs(QgsCoordinateReferenceSystem.fromSrsId(3452), QgsProject.instance().transformContext())
        da.setEllipsoid("NONE")

        # We check both the measured length AND the units, in case the logic regarding
        # ellipsoids and units changes in future
        distance = da.measureLine(QgsPointXY(1, 1), QgsPointXY(2, 3))
        units = da.lengthUnits()

        print(("measured {} in {}".format(distance, QgsUnitTypes.toString(units))))
        assert ((abs(distance - 2.23606797) < 0.00000001 and units == QgsUnitTypes.DistanceDegrees) or
                (abs(distance - 248.52) < 0.01 and units == QgsUnitTypes.DistanceMeters))

        da.setEllipsoid("WGS84")
        distance = da.measureLine(QgsPointXY(1, 1), QgsPointXY(2, 3))
        units = da.lengthUnits()

        print(("measured {} in {}".format(distance, QgsUnitTypes.toString(units))))
        # should always be in Meters
        self.assertAlmostEqual(distance, 247555.57, delta=0.01)
        self.assertEqual(units, QgsUnitTypes.DistanceMeters)

        # test converting the resultant length
        distance = da.convertLengthMeasurement(distance, QgsUnitTypes.DistanceNauticalMiles)
        self.assertAlmostEqual(distance, 133.669, delta=0.01)

        # now try with a source CRS which is in feet
        da.setSourceCrs(QgsCoordinateReferenceSystem.fromSrsId(27469), QgsProject.instance().transformContext())
        da.setEllipsoid("NONE")
        # measurement should be in feet
        distance = da.measureLine(QgsPointXY(1, 1), QgsPointXY(2, 3))
        units = da.lengthUnits()
        print(("measured {} in {}".format(distance, QgsUnitTypes.toString(units))))
        self.assertAlmostEqual(distance, 2.23606797, delta=0.000001)
        self.assertEqual(units, QgsUnitTypes.DistanceFeet)

        # test converting the resultant length
        distance = da.convertLengthMeasurement(distance, QgsUnitTypes.DistanceMeters)
        self.assertAlmostEqual(distance, 0.6815, delta=0.001)

        da.setEllipsoid("WGS84")
        # now should be in Meters again
        distance = da.measureLine(QgsPointXY(1, 1), QgsPointXY(2, 3))
        units = da.lengthUnits()
        print(("measured {} in {}".format(distance, QgsUnitTypes.toString(units))))
        self.assertAlmostEqual(distance, 0.67953772, delta=0.000001)
        self.assertEqual(units, QgsUnitTypes.DistanceMeters)

        # test converting the resultant length
        distance = da.convertLengthMeasurement(distance, QgsUnitTypes.DistanceFeet)
        self.assertAlmostEqual(distance, 2.2294, delta=0.001)

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def testLengthMeasureAndUnits(self):
        """Test a variety of length measurements in different CRS and ellipsoid modes, to check that the
           calculated lengths and units are always consistent
        """

        da = QgsDistanceArea()
        da.setSourceCrs(3452)
        da.setEllipsoidalMode(False)
        da.setEllipsoid("NONE")
        daCRS = QgsCoordinateReferenceSystem()
        daCRS.createFromSrsId(da.sourceCrs())

        # We check both the measured length AND the units, in case the logic regarding
        # ellipsoids and units changes in future
        distance = da.measureLine(QgsPoint(1, 1), QgsPoint(2, 3))
        units = da.lengthUnits()

        print "measured {} in {}".format(distance, QgsUnitTypes.toString(units))
        assert ((abs(distance - 2.23606797) < 0.00000001 and units == QGis.Degrees) or
                (abs(distance - 248.52) < 0.01 and units == QGis.Meters))

        da.setEllipsoid("WGS84")
        distance = da.measureLine(QgsPoint(1, 1), QgsPoint(2, 3))
        units = da.lengthUnits()

        print "measured {} in {}".format(distance, QgsUnitTypes.toString(units))
        assert ((abs(distance - 2.23606797) < 0.00000001 and units == QGis.Degrees) or
                (abs(distance - 248.52) < 0.01 and units == QGis.Meters))

        da.setEllipsoidalMode(True)
        distance = da.measureLine(QgsPoint(1, 1), QgsPoint(2, 3))
        units = da.lengthUnits()

        print "measured {} in {}".format(distance, QgsUnitTypes.toString(units))
        # should always be in Meters
        self.assertAlmostEqual(distance, 247555.57, delta=0.01)
        self.assertEqual(units, QGis.Meters)

        # now try with a source CRS which is in feet
        da.setSourceCrs(27469)
        da.setEllipsoidalMode(False)
        # measurement should be in feet
        distance = da.measureLine(QgsPoint(1, 1), QgsPoint(2, 3))
        units = da.lengthUnits()
        print "measured {} in {}".format(distance, QgsUnitTypes.toString(units))
        self.assertAlmostEqual(distance, 2.23606797, delta=0.000001)
        self.assertEqual(units, QGis.Feet)

        da.setEllipsoidalMode(True)
        # now should be in Meters again
        distance = da.measureLine(QgsPoint(1, 1), QgsPoint(2, 3))
        units = da.lengthUnits()
        print "measured {} in {}".format(distance, QgsUnitTypes.toString(units))
        self.assertAlmostEqual(distance, 0.67953772, delta=0.000001)
        self.assertEqual(units, QGis.Meters)

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def testCrs(self):
        # test setting/getting the source CRS
        da = QgsDistanceArea()

        # try setting using a crs id
        da.setSourceCrs(3452)
        self.assertEqual(da.sourceCrsId(), 3452)

        # try setting using a CRS object
        crs = QgsCoordinateReferenceSystem(3111, QgsCoordinateReferenceSystem.EpsgCrsId)
        da.setSourceCrs(crs)
        self.assertEqual(da.sourceCrsId(), crs.srsid())

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def regularMatrix(self, parameters, context, source, inField, target_source, targetField,
                      nPoints, feedback):

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

        inIdx = source.fields().lookupField(inField)
        targetIdx = target_source.fields().lookupField(targetField)

        index = QgsSpatialIndex(target_source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([]).setDestinationCrs(source.sourceCrs(), context.transformContext())), feedback)

        first = True
        sink = None
        dest_id = None
        features = source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([inIdx]))
        total = 100.0 / source.featureCount() if source.featureCount() else 0
        for current, inFeat in enumerate(features):
            if feedback.isCanceled():
                break

            inGeom = inFeat.geometry()
            if first:
                featList = index.nearestNeighbor(inGeom.asPoint(), nPoints)
                first = False
                fields = QgsFields()
                input_id_field = source.fields()[inIdx]
                input_id_field.setName('ID')
                fields.append(input_id_field)
                for f in target_source.getFeatures(QgsFeatureRequest().setFilterFids(featList).setSubsetOfAttributes([targetIdx]).setDestinationCrs(source.sourceCrs(), context.transformContext())):
                    fields.append(QgsField(str(f[targetField]), QVariant.Double))

                (sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
                                                       fields, source.wkbType(), source.sourceCrs())
                if sink is None:
                    raise QgsProcessingException(self.invalidSinkError(parameters, self.OUTPUT))

            data = [inFeat[inField]]
            for target in target_source.getFeatures(QgsFeatureRequest().setSubsetOfAttributes([]).setFilterFids(featList).setDestinationCrs(source.sourceCrs(), context.transformContext())):
                if feedback.isCanceled():
                    break
                outGeom = target.geometry()
                dist = distArea.measureLine(inGeom.asPoint(),
                                            outGeom.asPoint())
                data.append(dist)

            out_feature = QgsFeature()
            out_feature.setGeometry(inGeom)
            out_feature.setAttributes(data)
            sink.addFeature(out_feature, QgsFeatureSink.FastInsert)
            feedback.setProgress(int(current * total))

        return {self.OUTPUT: dest_id}

# 需要导入模块: from qgis.core import QgsDistanceArea [as 别名]
# 或者: from qgis.core.QgsDistanceArea import setSourceCrs [as 别名]
    def calculate( self, layer, fieldName, expression ):
        if ( layer.featureCount() == 0 ):
            self.msg.show( "[Info] * No existing features on layer " + layer.name() + " to calculate expression.", 'info', True )
            return

        expression = QgsExpression( expression )
        if expression.hasParserError():
            self.msg.show( QApplication.translate( "AutoFields-FieldCalculator", "[Error] (Parsing) " ) + \
                expression.parserErrorString(), 'critical' )
            return
        
        context = QgsExpressionContext()
        context.appendScope( QgsExpressionContextUtils.globalScope() )
        context.appendScope( QgsExpressionContextUtils.projectScope() )
        context.appendScope( QgsExpressionContextUtils.layerScope( layer ) )
        context.setFields( layer.fields() )

        if expression.needsGeometry():
            if self.iface:
                # This block was borrowed from QGIS/python/plugins/processing/algs/qgis/FieldsCalculator.py 
                da = QgsDistanceArea()
                da.setSourceCrs( layer.crs().srsid() )
                da.setEllipsoidalMode( self.iface.mapCanvas().mapSettings().hasCrsTransformEnabled() )
                da.setEllipsoid( QgsProject.instance().readEntry( 'Measure', '/Ellipsoid', GEO_NONE )[0] )
                expression.setGeomCalculator( da )
                if QGis.QGIS_VERSION_INT >= 21400: # Methods added in QGIS 2.14
                    expression.setDistanceUnits( QgsProject.instance().distanceUnits() ) 
                    expression.setAreaUnits( QgsProject.instance().areaUnits() )
        
        expression.prepare( context )

        fieldIndex = layer.fieldNameIndex( fieldName )
        if fieldIndex == -1:
            return           
        field = layer.fields()[fieldIndex]
        
        dictResults = {}
        for feature in layer.getFeatures():
            context.setFeature( feature )
            result = expression.evaluate( context )
            if expression.hasEvalError():
                self.msg.show( QApplication.translate( "AutoFields-FieldCalculator", "[Error] (Evaluating) " ) + \
                    expression.evalErrorString(), 'critical' )
                return
                
            dictResults[feature.id()] = { fieldIndex: field.convertCompatible( result ) }
            

        layer.dataProvider().changeAttributeValues( dictResults )
        
        self.msg.show( "[Info] * An expression was calculated on existing features of layer " + layer.name() + ", field " + fieldName + ".", 'info', True )