psitsNOT (“Photoshop it’s NOT!”) is an AJAX powered image editor for
Rails. Although it doesn’t pretend to be feature-rich, psitsNOT lets you
rotate and crop; adjust brightness, contrast, and color balance; then
reduce grain, enhance color contrast, sharpen, and set the final size of
an image. It does a great job at enhancing digital photos for display on
the web.
A demo site is online at http://psitsnot.alevans.com
(You’ll need an OpenID URL to log in and edit photos! See the links on
the login page.)
psitsNOT is now available as a Rails Engine! Not only that, but when its
name gets Railsified, it comes out to p_sitsnot_engine! 
Following the instructions in the README, you can build a basic
image-editing site in 15-30 minutes. After that, like everything else in
Rails, you can “cut to fit, paint to match”.
You can get the PSitsnotEngine (or p_sitsnot_engine) from
http://svn.openprofile.net/plugins/p_sitsnot_engine
NOTE!! psitsNOT requires RMagick! Timothy H., the writer of RMagick,
strongly advises that you update your installation to at least version
1.11.1. psitsNOT works reliably with version 1.10.1, but a memory leak
could occur under certain unusual circumstances.
–Al Evans