Image data is returned if a request successfully completes, and if the request either does not include a req= command, or if req=img or req=tmb.
The HTTP response MIME type is determined by
fmt=, or, if
fmt= is not specified, it is
The HTTP response status is ‘200 OK’ if the request method was an unconditional
The server may reply with status ‘304’ (not modified) and not return any image data in response to a conditional
GET request (which includes a valid