QGIS gdal merge not working

Question

I'm getting this error when trying to merge 5 different files:

2020-08-25T15:52:53     WARNING    Traceback (most recent call last): File "C:/Users/.../AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\interference_zone\interference_zone.py", line 362, in interference_calculation
              processing.run("gdal:merge", parameters)
              File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\tools\general.py", line 106, in run
              return Processing.runAlgorithm(algOrName, parameters, onFinish, feedback, context)
              File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\core\Processing.py", line 137, in runAlgorithm
              raise QgsProcessingException(msg)
             _core.QgsProcessingException: Unable to execute algorithm
             Incorrect parameter value for INPUT

This is the code I am running:

parameters = {
        'INPUT': final_result_layers,
        'PCT' : True,
        'SPERATE' : True,
        'OUTPUT' : outputfile_path
    }
processing.run("gdal:merge", parameters)

The final_result_layers is a list of type QgsRasterLayer.

Answer 1

Input of function gdal:merge must be a list of path and not a list of QgsRasterLayer.

Here is a snippet wich works with your code:

layer_1 = QgsProject.instance().mapLayersByName("Fusionné")[0]
layer_2 = QgsProject.instance().mapLayersByName("Interpolé")[0]

final_result_layers = []
final_result_layers.append(layer_1.dataProvider().dataSourceUri())
final_result_layers.append(layer_2.dataProvider().dataSourceUri())

outputfile_path = "/home/jules.grillot/Bureau/test.tif"
parameters = {
        'INPUT': final_result_layers,
        'PCT' : True,
        'SPERATE' : True,
        'OUTPUT' : outputfile_path
    }
processing.runAndLoadResults("gdal:merge", parameters)