Many thanks to Batch Resize Images Quickly in the OS X Terminal for giving me a quick and perfectly adequate way to make thumbnails for a web page from 32 photos:

  sips -Z 256 *.jpg 

Destructive! Work on copies.

@Miraz oh… oh that’s handy

@Miraz That’s such a clever one-liner. To everyone following along at home: keep copies of your originals as this is a destructive action.

@sod I first tried some Automator actions and the results were terrible. This command did a nice job.