topic Re: Composing raster functions with parameters for the input raster(s) in ArcGIS API for Python Questions

Composing raster functions with parameters for the input raster(s)

DavidJohnson5 — Sun, 12 Dec 2021 08:59:37 GMT

I'm trying to figure out how to wrap a raster function chain into a python function that has parameters for the input raster(s) of the function chain. I also need to display the output in the map widget.

My eventual goal is to create wrappers for function chains which have multiple input branches. But for now, here is a very simple example I have tried which requires only one input raster parameter.

# code for context.

type(dem_item)

arcgis.gis.item

dem_item.layers

# python wrapper function

def slope_template(in_ras):

return

{

"rasterFunction" : "Slope",

"rasterFunctionArguments" : {

"DEM" : in_ras

}

# Add the output of the function to the map widget

map.add_layer(slope_template(dem_item.layers[0]))

Running this code produces the following error.

---------------------------------------------------------------------------TypeError                                 Traceback (most recent call last)<ipython-input-26-4095d219143b> in <module>()----> 1 map1.add_layer(slope_template(dem_item.layers[0])) C:\Program Files\ArcGIS\Pro\bin\Python\envs\arcgispro-py3\lib\site-packages\arcgis\widgets\__init__.py in add_layer(self, item, options)    142     143             self._addlayer = json.dumps(js_layer)--> 144         elif 'layers' in item:  # items as well as services    145             if item.layers is None:     146                 raise RuntimeError('No layers accessible/available in this item or service') TypeError: argument of type 'NoneType' is not iterable

Re: Composing raster functions with parameters for the input raster(s)

Anonymous User — Wed, 12 Apr 2017 19:20:31 GMT

David we are working on a similar concept internally for the next release. With that you can access raster functions as Python functions and greatly simplifies how you use and chain them.

Meanwhile, checkout the extract_bands funciton in https://developers.arcgis.com/python/guide/using-imagery-layers/#Composing-raster-functions which talks about chaining raster functions and writing a method around it. You can use that as a starting point.

Re: Composing raster functions with parameters for the input raster(s)

DavidJohnson5 — Wed, 12 Apr 2017 20:15:38 GMT

Atma, that sounds very cool to be able to access raster functions as python functions. I look forward to getting my hands on that capability! It's good to know your team is already working on it. Thanks for the tip. That link you provided actually was my starting point for trying out this idea. Thanks again!