Input parameters for i.topo.corr algorithm in QGIS Python console

Question

I'm trying to run the i.topo.corr algorithm in the QGIS Python console, on a multi-band WorldView image. I'm still getting an error that the input value is incorrect. For this algorithm, the inputs are the bands on which the algorithm will be applied:

input: Name of reflectance raster maps to be corrected topographically

Parameter type: QgsProcessingParameterMultipleLayers

Accepted data types:
    - list[str]: list of layer identifiers
    - list[str]: list of layer names
    - list[str]: layer source list
    - list[QgsMapLayer]
    - QgsProperty

According to the documentation (https://docs.qgis.org/3.4/en/docs/user_manual/processing/console.html#processing-console), the value for a multiple input is:

« Multiple input. The value is a string with input descriptors separated by semicolons (;). As in the case of single layers or tables, each input descriptor can be the data object name, or its file path. Simply use a string with the name that identifies the data object to use (the name it has in the QGIS Table of Contents) or a filename. »

There is my code in QGIS Python console. I don't know how to refer to the bands of my image in the input parameter:

import processing

processing.run("grass7:i.topo.corr", {'INPUT': 'ImageName_band1';'ImageName_band2';'ImageName_band3',
    'BASEMAP': 'Illumination_model_name',
    'ZENITH': 69.7,
    'METHOD': 2,
    'OUTPUT': r'output_directory'})

I tried many thing for the bands in imput parameter: imageName.1, imageName_1, imageName@1, imageName_B1, etc.

Answer 1

If each band of the multiband raster exists as independent files in your hardrive then you can list those files names. Example as list:

input = ['C:/Users/Eloisa/band1.tif', 'C:/Users/Eloisa/band2.tif', 'C:/Users/Eloisa/band3.tif']

If you only have the multiband raster then you can extract each single band using GDAL. Assuming your image is a TIFF:

from osgeo import gdal
multiband = 'C:/Users/Javier/multibanda.tif'
in_ds = gdal.Open(multiband)
gtiff_driver = gdal.GetDriverByName('GTiff')
for i in range(1, in_ds.RasterCount+1):
    in_band = in_ds.GetRasterBand(i)
    out_ds = gtiff_driver.Create('C:/Users/Javier/band{0}.tif'.format(i), in_band.XSize, in_band.YSize, 1, in_band.DataType)
    out_ds.SetProjection(in_ds.GetProjection())
    out_ds.SetGeoTransform(in_ds.GetGeoTransform())
    in_data = in_band.ReadAsArray()
    out_band = out_ds.GetRasterBand(1)
    out_band.WriteArray(in_data)
out_ds.FlushCache()