Getting Pixels from Shape Drawn Using ofGraphics Methods

I drew a circle using ofDrawCircle() and I want to the circle’s edge to gradually fade into the background by modifying the alpha values in the circle. I’ve been thinking of achieving this by grabbing the screen pixels, modifying them and putting them into an fbo object.

Is there a way to get pixels drawn by calling ofDrawCircle() into an ofPixel object? The documentation seems to suggest that it is possible. All the examples I’ve seen manipulate images only.

Thanks in advance.