Hello there; love spek and use it regularly to understand encoding quality of my music library.

So regularly, in fact, that I'd like to generate output in batch (to compare files in a set, for instance). Would it be possible to have a command-line option that generates one or more PNGs and exits with a zero return value if the run was successful? Something like

-b, --batch generate PNG image file(s) and exit; filenames are suffixed with ".png"

would be fine for my use case, as it would allow something like spek -b ~/00MUZAK/*mp3, outputting Spek files following the format ~/00MUZAK/*.mp3.png.

I considered adding a comment to issue 169, but the request there is not about generating the PNGs, but rather outputing a text value; I'm not looking for that, as I think the PNG is more useful when comparing. Note that a -o option to allow customizing the path/filename might be useful but I personally wouldn' need it.