Using imagemagick to create vibrant images
I'm in the process of helping out a friend who has a bunch of inventory pics. Most appear faded/washed out, and generally dull. I really like the effect as described here: http://www.abeautifulmess.com/2012/07/how-to-create-vibrant-color-photographs.html, however, I'm trying to do this using ImageMagick because there are hundreds (if not thousands) of images to convert, and I'd like to be able to convert them in an automated manner.
They're also on S3, so the process would be: download -> convert -> upload.
I've played around with modifying the brightness in imagemagick (http://www.imagemagick.org/www/command-line-options.html#brightness-contrast) but that alone doesn't seem to help. Are there options I'm missing or steps I can do that would help?
Screening an image with itself in photoshop is equivalent to either
-negate -gamma 0.5 -negate or
-fx '1-((1-u)^2)' in ImageMagick (the first one is probably faster,
-fx is notoriously slow.)