The browser will not download the picture automatically for you, the address bar will just use the URL provided, and do the DNS lookup and render/download the data/image/html in the client machine from the server.
And for this reason, only we have clientside scripting language to tell what to do with the downloaded contents. Now to download the image automatically what you can do is download a javascript file that will execute in the client machine and download the image automatically.
just trigger the download on javascript/jquery onLoad event
refer this for more info: Force Download an Image Using Javascript