Not quite what you asked, but we often need to do something similar, with a greyed out "reverse mask" around various watershed polygons. We have this function set up to turn any polygon / feature class into a cutout of itself, inside a circular buffer of whatever distance. If you pass it fields, you can use these reverse masks inside a Map Series too, to highlight specific regions as you loop through.
This would require that your graphics layer be a feature class.
import arcpy
import os
def create_reverse_mask(input_fc, output_name, buffer_dist=10000, fields=[]):
"""
Creates a 'cutout' mask from input polygons and adds it to the map
with 75% transparent grey symbology.
input_fc : Layer in TOC, or path to feature class
output_name : Can be a full path, or just the name (in which case, save to scratchGDB)
buffer_dist : Map Units. Set as big as needed for layout
fields : Define the fields to copy over from input (or leave empty)
"""
# Prevent double-adding to TOC
arcpy.env.addOutputsToMap = False
# --- Path Handling ---
if os.path.isabs(output_name):
out_dir = os.path.dirname(output_name)
out_base = os.path.basename(output_name)
output_fc = output_name
else:
out_dir = arcpy.env.scratchGDB
out_base = output_name
output_fc = os.path.join(out_dir, out_base)
# --- Initialize Feature Class ---
if not arcpy.Exists(output_fc):
sr = arcpy.Describe(input_fc).spatialReference
arcpy.management.CreateFeatureclass(
out_path=out_dir,
out_name=out_base,
geometry_type="POLYGON",
template=input_fc,
spatial_reference=sr
)
print(f"Created: {output_fc}")
# --- Processing ---
cursor_fields = ["SHAPE@"] + fields
with arcpy.da.InsertCursor(output_fc, cursor_fields) as i_cursor:
with arcpy.da.SearchCursor(input_fc, cursor_fields) as s_cursor:
for row in s_cursor:
geom = row[0]
if geom:
buff = geom.buffer(buffer_dist)
mask_geom = buff.difference(geom)
i_cursor.insertRow((mask_geom,) + row[1:])
# --- Symbology (CIM) ---
aprx = arcpy.mp.ArcGISProject("CURRENT")
m = aprx.activeMap
# Manually add the layer so we can grab the object
new_lyr = m.addDataFromPath(output_fc)
cim = new_lyr.getDefinition('V3')
# 25% Opaque = 75% Transparent
grey_fill = [128, 128, 128, 25]
# Iterate through symbol layers to update fill and disable stroke
for sl in cim.renderer.symbol.symbol.symbolLayers:
if isinstance(sl, arcpy.cim.CIMSolidFill):
sl.color.values = grey_fill
if isinstance(sl, arcpy.cim.CIMSolidStroke):
sl.enable = False
new_lyr.setDefinition(cim)
print(f"Done. Layer '{out_base}' added.")
# Example Call:
#create_reverse_mask("lightofdaypolygon", "reversemask", 100000)
