How can I get a map image from an ArcGIS mapserver centered on a single feature?

Question

I have a Python program that is not using arcpy. I need to get an image from a mapservice centered on a single feature using the REST api.

I can call the export method to get a map image:

http://<server>/arcgis/rest/services/<name>/MapServer/export?bbox=<bounds>&f=image

I can also query the mapservice layer using a where clause and get the feature geometry (in my case, it's going to be a polygon feature).

Without using arcpy, is there an easy way to take the polygon's geometry, get a rectangular extent to generate the bounding box necessary to call the export?

What would be ideal is if I could just say "Give me a map image centered on a feature from a layer defined by this where clause" but, unless I'm missing something, you can't do this in one step. Neither can I figure out how to do a Query on a layer and get the extent back instead of just the feature geometry.

Answer 1

You can use my restapi module. It is very simple to do these kinds of things:

import restapi
import os

url = 'http://gis.mda.state.mn.us/arcgis/rest/services/MN_Agriculture_EAB_Detection/MapServer'

# reference map service
mapService = restapi.MapService(url)

# reference quarantine county layer so we can get a single feature
quarantines = mapService.layer('emerald ash borer quarantines') # could also just use the service id of 3

# query this to get a single feature
fs = quarantines.query(where="COUNTYNAME = 'Hennepin'")

featureGeom = restapi.Geometry(fs) # will grab the first polygon

# now export map png
png = r'C:\TEMP\test_export.png'
r = mapService.export(png, bbox=featureGeom.envelope(), bboxSR=mapService.spatialReference)
os.startfile(png)

This module does NOT require arcpy, but will use it if available. Otherwise it uses open source alternatives.