您可以通过以下方式在独立(无GUI)模式下运行QGIS处理算法:
import sys
from qgis.core import (
QgsApplication,
QgsProcessingFeedback,
QgsVectorLayer
)
# See /gis//a/155852/4972 for details about the prefix
QgsApplication.setPrefixPath('/usr', True)
qgs = QgsApplication([], False)
qgs.initQgis()
# Append the path where processing plugin can be found
sys.path.append('/docs/dev/qgis/build/output/python/plugins')
import processing
from processing.core.Processing import Processing
Processing.initialize()
layer1 = QgsVectorLayer('/path/to/geodata/lines_1.shp', 'layer 1', 'ogr')
layer2 = QgsVectorLayer('/path/to/geodata/lines_2.shp', 'layer 2', 'ogr')
# You can see what parameters are needed by the algorithm
# using: processing.algorithmHelp("qgis:union")
params = {
'INPUT' : layer1,
'OVERLAY' : layer2,
'OUTPUT' : '/path/to/output_layer.gpkg|layername=output'
}
feedback = QgsProcessingFeedback()
res = processing.run('qgis:union', params, feedback=feedback)
res['OUTPUT'] # Access your output layer
本机算法
现在,如果要使用本机算法(即,来自本机提供程序的算法,其算法用C ++编写),则需要在初始化Processing之后添加提供程序:
import sys
from qgis.core import (
QgsApplication,
QgsProcessingFeedback,
QgsVectorLayer
)
from qgis.analysis import QgsNativeAlgorithms
# See /gis//a/155852/4972 for details about the prefix
QgsApplication.setPrefixPath('/usr', True)
qgs = QgsApplication([], False)
qgs.initQgis()
# Append the path where processing plugin can be found
sys.path.append('/docs/dev/qgis/build/output/python/plugins')
import processing
from processing.core.Processing import Processing
Processing.initialize()
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
layer = QgsVectorLayer('/path/to/geodata/lines.shp', 'my layer', 'ogr')
# You can see what parameters are needed by the algorithm
# using: processing.algorithmHelp("native:extractvertices")
params = {
'INPUT': layer,
'OUTPUT': 'memory:'
}
feedback = QgsProcessingFeedback()
res = processing.run("native:extractvertices", params, feedback=feedback)
res['OUTPUT'] # Access your output layer