It's one of those curves that's much easier to define implicitly than to explicitly find the border. If you don't mind testing each pixel to see if it should be

It's one of those curves that's much easier to define implicitly than to explicitly find the border. If you don't mind testing each pixel to see if it should be "in" or "out" then you can draw a picture of it easily. But if you want an explicit function for the boundary or avoid calculating much of the pixels, you'll need something like marching squares or more math to find it. The SVG solution here is nice in that increasing the resolution doesn't require you to do any more computation to determine where the border should be, and the border will always be exact and smooth; you even get antialiasing "for free".