Resizing and reformatting images should a straight-forward exercise, after a few false starts with Photoshop and ImageMaverick, I found a nice and simple solution.

There are several options, Photoshop's 'Automate' feature or ImageMaverick, but more often than not they are overkill. (Or as in the case of Photoshop, you run into some unspecified errors, which leave you with thousands of open windows... Neither elegant nor effective).

I wish there were a simple command-line utility that would allow for the painless resizing and reformatting of images. Luckily there is, it's called sips - scriptable image processing system.

sips -s format jpeg -s formatOptions 80 -Z 480 *.png --out jpeg

The "-s" modifier means "set", -s format jpeg means set the output format to jpeg, -s formatOptions 80 means set the jpeg quality to 80.

-Z 480 specifies that the largest side of the image should be 480px.

*.png are the input files.

--out jpeg is the output directory. Call it anything you like, but make sure it exists.