Turning a screen into a virtual web cam

Is there an app (preferable a Mac app) that will turn an area of your screen into a virtual web cam, such that it would be available as an input source for other a开发者_如何学Pythonpps that want to access your web cam?

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CamTwist (Mac)

Allows you to turn your desktop into a cam image. And it is free.

Download it here

If you're on Windows take a look at ManyCam

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or how about:

webcamstudio (Linux)

it's java so there should be ports to most systems?

http://www.ws4gl.org/

http://code.google.com/p/webcamstudio/

-or-

CamCamX (Mac)

a bit more on the shady side ($99!) but i've installed it and it seems like it could be snazzy, post-licensing... however it's not as great as CamTwist...

http://b-l-a-c-k-o-p.com/CamCamX.html