based on code from Playing With Chaos (Keith Peters) and The Fractal Flame Algorithm (Scott Draves, Eric Reckase)
more fractal functions makes colour jumps smoother and increases 'wispiness'
each fractal will be assigned a colour from this gradient. if the fractal is chosen during iteration its colour will be added to the canvas. the renderer only uses the hue of the colours that you select.
note that some fractals may be very dim, or mostly black. this is because fractal parameters are chosen randomly, so the functions may tend towards points outside of the viewport. hit r to restart during render if you don't like the results.