Circlipse v.1.0, for Adobe Illustrator

Circlipse is an Illustrator script that enables quick and precise drawing of ellipses and circles, even when a traced ellipse is partly obscured. It is inspired by a cool Inkscape plugin and is intended for similar uses. However, it is a purely custom implementation in Javascript that emphasizes precision. It is heavily commented for anyone interested in the source code.

How to Use

1. Copy the JSX script file to the scripts folder. If you can find your Illustrator folder, go from there to Presets and then to Scripts. (The Scripts folder may itself be wrapped under a locale-named folder, like en_US.)
2. Start (or restart) Illustrator and open the target document. Save any work, just in case!
3. Set the stroke and fill properties you want.
4. With the Pen Tool, plot either three anchor points for a circle or five for an ellipse, with each point lying at the outline of the path desired.
5. Select File -> Scripts -> circlipse. If the script calculates the ellipse or circle correctly, you're done! Otherwise, pay close attention to any alert messages.

Further Development

This script may be useful for other Adobe products, so if requested, I can attempt making it run elsewhere.

Recent Updates

An older version of this script was prone to failing if the top layer were hidden. I do not recall it being documented anywhere, but the active layer has properties in the API similar to that of the document itself. Thus, the current layer is now manipulated directly in lieu of adding an ellipse to the top layer as was happening before, which should improve workflow. I have also added the MIT license and confirmed on my copy of CS6 a while back.