A Barnsley fern generator

I was reading about the Barnsley fern on Wikipedia, and was inspired to write a generator to work in web browsers. It uses HTML 5 so you need an up-to-date web browser; if you don't see anything appear on the right you need to update your browser. You can choose below from a number of ferns, which I've shamelessly stolen from here or from Barnsley's book, or enter your own values and see what happens.

The default values are about right. More than a million points makes for slow fractal generation (though the plotting should not slow down); too many more and you run out of memory. Zoom in by increasing the scale factor.

Enter your affine transformations and probabilites:

a b c d e f p

Choose a fern color:

Scale factor: