From a Java web app, presumably using ArcGIS Rest services, I need to determine the envelope to use in an ExportWebMapTask.
The envelope will have coordinates based on a known map image output dimensions (which will be specified in ExportWebMapTaskexportOptions.outputSize) - in the case of the attached example the image size is 850x927.
The envelope should enclose a polygon with the specified minimum buffer size (buffer on either side of the polygon for the side of the envelope with the longest edge) - in the example the minimum buffer size is 200.
I don't think it will be relevant to the solution but the polygon feature layer and other operational layers and the basemap all use different spatial references.
How do I get the envelope for the buffered, centered polygon?