topic Multipart color ramp for script tool raster output symbology with JSON in Python Questions

Multipart color ramp for script tool raster output symbology with JSON

jrolson14 — Wed, 11 Jun 2025 20:20:38 GMT

Hello, I'm trying to figure out how to properly set up a JSON string to get a multipart color ramp for the output (raster) symbology in a script tool. I've been looking all over the internet but can't find a working example specifically for getting a multipart color ramp. Here's what it looks like:

if __name__ == "__main__": in_cdp = arcpy.GetParameterAsText(0) in_gdb = arcpy.GetParameterAsText(1) in_ocs = arcpy.GetParameterAsText(2) in_rff = arcpy.GetParameterAsText(3).split(";") in_srr = bool(arcpy.GetParameterAsText(4)) final_out = arcpy.GetParameterAsText(5) main_process(in_cdp, in_gdb, in_ocs, in_rff, in_srr, final_out) # Output symbology json_str = '''{ "type": "rasterStretch", "colorRamp": { "type": "multipart", "colorRamps": [ { "type": "algorithmic", "fromColor": [56, 161, 208, 255], "toColor": [241, 251, 124, 255], "algorithm": "esriHSVAlgorithm" }, { "type": "algorithmic", "fromColor": [241, 251, 124, 255], "toColor": [239, 40, 32, 255], "algorithm": "esriHSVAlgorithm" } ] } }''' arcpy.SetParameterSymbology(5, f"JSONRENDERER={json_str}")

I've tried tweaking lots of things but every time I just still get the default black to white color ramp. I'm trying to mimic the "Prediction" color ramp available in the symbology pane when you set the symbology manually.

Here's how my parameter set up looks (only including the output's parameter for simplicity):

Label	Name	Data Type	Type	Direction	Description	Category	Filter	Dependency	Default	Environment	Symbology
Final Output	final	Raster Dataset	Required	Output

Anyone know what I'm doing wrong?

Re: Multipart color ramp for script tool raster output symbology with JSON

HaydenWelch — Fri, 13 Jun 2025 17:21:05 GMT

I think it's a formatting thing, Have you tried creating the symbology then saving it as a lyrx? You can either pass the path to that layer file as the symbology source, or copy and paste the parts you want into the json_str variable. The types key should be something like `CIMRaster...`

Re: Multipart color ramp for script tool raster output symbology with JSON

jrolson14 — Wed, 18 Jun 2025 17:07:51 GMT

Hi thanks for the reply! I prefer using the JSON method for the sake of portability (not having to make sure the user has the same .lyrx file). I tried copying the JSON from a lyrx file made from output of the tool set to the Prediction color ramp but still no luck and it seems like the symbology JSON in the lyrx is specific to that raster's values.