raster – How to Create QGIS Processing Script Parameter with Multiple Rasters

pyqgisqgis-processingraster

I'm trying to create a QGIS script that would use multiple Raster layers as an input parameter. But QgsProcessingParameterRasterLayer only gives a single Raster as input and QgsProcessingParameterMultipleLayers defaults to a multiselect of Vector layers.

I'm probably missing something easy, but how can I get the multiselect to work with raster files like the Merge Rasters tool does for example?

Best Answer

Just pass the QgsProcessing.SourceType to the QgsProcessingParameterMultipleLayers class constructor:

def initAlgorithm(self, config=None):
    self.addParameter(QgsProcessingParameterMultipleLayers(
        self.INPUT,
        self.tr("Input rasters"),
        QgsProcessing.TypeRaster))

Related Solutions

QGIS Python Script Loop for Raster Calculator – Detailed Guide

You could use something like the following:

import processing

lddLrs = qgis.utils.iface.legendInterface().layers()
path = "path/to/results//"
for lyr in lddLrs:
    processing.runalg("saga:rastercalculator", lyr, None, "(a/a)*a", True, 7, path + lyr.name() + "_suffix.tif")

EDIT :

If you want to use the QgsRasterCalculator, you could try using the following (based on this post):

from qgis.analysis import QgsRasterCalculatorEntry, QgsRasterCalculator

lddLrs = qgis.utils.iface.legendInterface().layers()
path = "path/to/results"
for lyr in lddLrs:
    entries = []
    ras = QgsRasterCalculatorEntry()
    ras.ref = 'ras@1'
    ras.raster = lyr
    ras.bandNumber = 1
    entries.append( ras )
    calc = QgsRasterCalculator( '(ras@1 / ras@1) * ras@1', path + lyr.name() + "_suffix.tif", 'GTiff', lyr.extent(), lyr.width(), lyr.height(), entries )
    calc.processCalculation()

UPDATE:

You can use the following code in a script which allows you to select individual rasters and run the calculator on them. I've changed the output to a folder so that multiple (or single) rasters can be output to the same directory but you can change this:

##NoDATA Background=name
##Raster=multiple raster
##OUT=folder

import glob, qgis
from PyQt4.QtCore import QFileInfo
from qgis.analysis import QgsRasterCalculatorEntry, QgsRasterCalculator
from qgis.core import QgsMapLayerRegistry, QgsRasterLayer

# Split rasters
layers = Raster.split(';')
output_path = OUT + "/"
suffix = "_suffix.tif"

for ras in layers:
    # Get layer object
    lyr = processing.getObjectFromUri(ras)
    entries = []    
    ras = QgsRasterCalculatorEntry()
    ras.ref = 'lyr@1'
    ras.raster = lyr
    ras.bandNumber = 1
    entries.append( ras )    
    calc = QgsRasterCalculator( '(lyr@1 / lyr@1) * lyr@1', output_path + lyr.name() + suffix, 'GTiff', lyr.extent(), lyr.width(), lyr.height(), entries )
    calc.processCalculation()

for results in glob.glob(output_path + "*" + suffix): 
    fileInfo = QFileInfo(results)
    path = fileInfo.filePath()
    baseName = fileInfo.baseName()
    layer = QgsRasterLayer(path, baseName)
    QgsMapLayerRegistry.instance().addMapLayer(layer)

PyQGIS – Inputting Raster and Processing Zonal Statistics with Custom Script

In addition to not setting is_child_algorithm=True, you are not retrieving your buffer distance parameter correctly. I have also added a few other improvements and simplifications- you do not need to manually add output features to feature sink, you can just use a QgsProcessingParameterVectorDestination and set it as the 'OUTPUT' for your final algorithm. You can also use QgsProcessingMultiStepFeedback so you get a nicely updating progress bar for the overall algorithm.

Try this modified script:

from PyQt5.QtCore import QCoreApplication, QVariant
from qgis.core import (QgsProcessing,
                       QgsProcessingException,
                       QgsProcessingAlgorithm,
                       QgsProcessingParameterFeatureSource,
                       QgsProcessingParameterVectorDestination,
                       QgsProcessingParameterNumber,
                       QgsProcessingParameterRasterLayer,
                       QgsProcessingMultiStepFeedback)
import processing


class ExampleProcessingAlgorithm(QgsProcessingAlgorithm):

    CENTROIDS = 'CENTROIDS'
    INPUT_RASTER_LAND_COVER = 'INPUT_RASTER_LAND_COVER'
    VEG_BUFFER_DIST = 'VEG_BUFFER_DIST'
    VUN_OUTPUT = 'VUN_OUTPUT'

    def tr(self, string):
        return QCoreApplication.translate('Processing', string)

    def createInstance(self):
        return ExampleProcessingAlgorithm()

    def name(self):
        return 'myscript'

    def displayName(self):
        return self.tr('My Script')

    def group(self):
        return self.tr('Example scripts')

    def groupId(self):
        return 'examplescripts'

    def shortHelpString(self):
        return self.tr("Example algorithm short description")

    def initAlgorithm(self, config=None):
        self.addParameter(
            QgsProcessingParameterRasterLayer(
                self.INPUT_RASTER_LAND_COVER,
                self.tr("Input a raster with land cover as distinct bands"),
                [QgsProcessing.TypeRaster]
            )
        )
        
        self.addParameter(
            QgsProcessingParameterFeatureSource(
                self.CENTROIDS,
                self.tr('Building centroids'),
                [QgsProcessing.TypeVectorPoint]
            )
        )
        
        self.addParameter(
            QgsProcessingParameterNumber(
                self.VEG_BUFFER_DIST,
                self.tr('Buffer distance around each property to assess vegetation cover (meters)')
            )
        )
        
        self.addParameter(
            QgsProcessingParameterVectorDestination(
                self.VUN_OUTPUT,
                self.tr('Vulnerability Output')
            )
        )

    def processAlgorithm(self, parameters, context, model_feedback):
        #each source layer is named, it is a two step process
        landcover = self.parameterAsRasterLayer(
            parameters,
            self.INPUT_RASTER_LAND_COVER,
            context
        )
        #if the input is invalid an error is raised
        if landcover is None:
            raise QgsProcessingException(self.invalidSourceError(parameters, self.INPUT_RASTER_LAND_COVER))
        
        #same as above, but with a vector not raster
        centroids = self.parameterAsVectorLayer(
            parameters,
            self.CENTROIDS,
            context
        )
        
        if centroids is None:
            raise QgsProcessingException(self.invalidSourceError(parameters, self.BUILDING_CENTROIDS))

        buffer_distance = self.parameterAsInt(parameters,
                                            self.VEG_BUFFER_DIST,
                                            context)
                                            
        steps = 5
        feedback = QgsProcessingMultiStepFeedback(steps, model_feedback)
        step = 1

        results = {}
        outputs = {}
        
        feedback.setCurrentStep(step)
        step+=1
        
        outputs['buffer_result'] = processing.run("native:buffer", {
            'INPUT': centroids,
            'DISTANCE': buffer_distance,
            'SEGMENTS': 5,
            'END_CAP_STYLE': 0,
            'JOIN_STYLE': 0,
            'MITER_LIMIT': 2,
            'DISSOLVE': False,
            'OUTPUT': 'TEMPORARY_OUTPUT'
        }, context=context, feedback=feedback, is_child_algorithm=True)
        results['buffer_result'] = outputs['buffer_result']['OUTPUT']
        
        feedback.setCurrentStep(step)
        step+=1
        outputs['zonal_statistics_result'] = processing.run("native:zonalstatisticsfb", {
        'INPUT': results['buffer_result'],
        'INPUT_RASTER': landcover,
        'RASTER_BAND':1,
        'COLUMN_PREFIX':'_',
        'STATISTICS':[0,1,2],
        'OUTPUT':'TEMPORARY_OUTPUT'
        },
        context=context, feedback=feedback, is_child_algorithm=True)
        results['zonal_statistics_result'] = outputs['zonal_statistics_result']['OUTPUT']
        
        feedback.setCurrentStep(step)
        step+=1
        outputs['join_1'] = processing.run("native:joinattributestable", {
        'INPUT':results['buffer_result'],
        'FIELD':'OBJECTID',
        'INPUT_2': results['zonal_statistics_result'],
        'FIELD_2':'OBJECTID',
        'FIELDS_TO_COPY':[],
        'METHOD':1,
        'DISCARD_NONMATCHING':False,
        'PREFIX':'',
        'OUTPUT':'TEMPORARY_OUTPUT'
        }, context=context, feedback=feedback, is_child_algorithm=True)
        results['join_1'] = outputs['join_1']['OUTPUT']
        
        feedback.setCurrentStep(step)
        step+=1
        #drop geometry of the multipolygons, so fields can be attached to point layer
        outputs['dropped_geoms'] = processing.run("native:dropgeometries", {
        'INPUT': results['join_1'],
        'OUTPUT':'TEMPORARY_OUTPUT'
        },
        context=context, feedback=feedback, is_child_algorithm=True)
        results['dropped_geoms'] = outputs['dropped_geoms']['OUTPUT']
        
        feedback.setCurrentStep(step)
        step+=1
        #attach fields without geometry to point layer
        outputs['join_2'] = processing.run("native:joinattributestable", {
        'INPUT':centroids,
        'FIELD':'OBJECTID',
        'INPUT_2': results['dropped_geoms'],
        'FIELD_2':'OBJECTID',
        'FIELDS_TO_COPY':['_count'],
        'METHOD':1,
        'DISCARD_NONMATCHING':False,
        'PREFIX':'',
        'OUTPUT':parameters[self.VUN_OUTPUT]
        }, context=context, feedback=feedback, is_child_algorithm=True)
        results['join_2'] = outputs['join_2']['OUTPUT']

        return results

Best Answer

Related Solutions

QGIS Python Script Loop for Raster Calculator – Detailed Guide

PyQGIS – Inputting Raster and Processing Zonal Statistics with Custom Script

Related Question