Output to file formats other than png

[samaaron]

It would be great if I could pass a flag into the view fn specifying which file format to export to. On the mac, I find ps2 easier to work with as it renders it as a zoomable pdf in Preview.

Could we just add another key to the opts map?

Although things aren't as simple as I'd expect, to get ps2 outputs to open in Preview properly, I have to use -Tps2 and specify a file extension of .ps, also I have to specify a longer temporty file name (I just use "foobar") :-)