SuperImage, and it’s messy API, are officially deprecated and replaced
by FlexImage
FlexImage is a plugin that stores binary image data in the database and
lets you pull it out at any size, quality, or crop. Combined with page
caching, this gives you an extremely flexible, fast, and extensible
system for managing images in your application.
FlexImage supports many of the same features as SuperImage, but through
a much cleaner and more consistent interface. Plus the internals has
been completely refactored and redocumented. It also has many new
capabilities:
* Cleaner API
* Multiple image rendering actions with their own defaults, or even
using different image classes
* Pre-processing images on upload
* Exposing of the resize! method allowing explicit processing of
images directly on the model
* Full model generator that creates model, tests, and migration
* Easier to extend with new image processing functions in the
future more for me than you 
SVN http://beautifulpixel.com/svn/plugins/flex_image
RDoc for full documentation
http://beautifulpixel.com/flex_image/index.html
Need to convert from SuperImage to FlexImage? Check out the easy as pie
conversion tips here:
http://beautifulpixel.textdriven.com/articles/2006/08/21/fleximage