Converting a data URL (aka data URI) to an image on the commandline (Mac OS X)
This is trivial, but was awfully hard to find via Google Search. Eventually had to give up and actually think about it. :-)
So, a data-URI looks something like the following:
data:image/png;base64,[and a stream of base64 characters here]
The part after the comma is literally the contents of the file (image or whatever), encoded in base64, so all you need to do is run base64 --decode on that part.
For example, with the whole data URL copied to the clipboard, I can do:
pbpaste | sed -e 's#data:image/png;base64,##' | base64 --decode > out.png
to get it into a png file.