Error when using r.series in a python script

Question

I’m writing a tool script in python and at a certain point I want to use the GRASS tool r.series. I want the algorithem to read all raster files from a folder and calculate the maximum with r.series. The thing is I’m getting the error: “Wrong parameter value: None” when using the code below:

##RasterMaxFinder=name
##Select_directory=Folder
##Save_results=Folder

import glob, os, processing

list = ( Select_directory + "/" + "*.tif" )

processing.runalg('grass7:r.series', list ,False,6,'-10000000000,10000000000',None,30.0, Save_results + "/" + "Output.tif")

It must have something to do with the extend, but I can't figure out what. When I'm using the tool directly in QGIS, erverything works fine. Any Ideas?

Answer 1

Yes, the extent probably has to be explicitly defined before you can run the algorithm. Seen a few posts about this. The following might work (note that I used grass:r.series and not grass7:r.series):

##RasterMaxFinder=name
##Select_directory=Folder
##Save_results=Folder

import glob, os, processing
from PyQt4.QtCore import QFileInfo
from qgis.core import QgsRasterLayer, QgsRectangle

os.chdir(Select_directory)
list = []
extent = QgsRectangle()
extent.setMinimal()
for raster in glob.glob("*.tif"):
    fileInfo = QFileInfo(raster)
    baseName = fileInfo.baseName()
    rlayer = QgsRasterLayer(raster, baseName)
    # Combine raster layers to list
    list.append(rlayer)
    # Combine raster extents
    extent.combineExtentWith(rlayer.extent())

# Get extent    
xmin = extent.xMinimum()
xmax = extent.xMaximum()
ymin = extent.yMinimum()
ymax = extent.yMaximum()
# Run algorithm
processing.runalg('grass:r.series', list ,False,6,'-10000000000,10000000000',"%f,%f,%f,%f"% (xmin, xmax, ymin, ymax),30.0, Save_results + "/" + "Output.tif")