I’m doing some playing around with image processing on HTML5 Canvas elements, and so I’ve hacked together a simple page for prototyping different algorithms. Check it out http://chofter.com/EffectPrototyping.
The code abstracts away most of the complexities of working with Canvas elements, and just lets you get down to what you need: your pixel manipulation algorithms. It provides a number of test images and examples to get you started, so have fun!
Oh and yes, it’s pretty ugly 
