What about if you check say, every 4 pixels rather than each one?
Already doing that ;) :D it was even SLOWER before.
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Thats a great screenie too. I tested it with pens and it can pinpoint the centre of the pen quite well.
Stand a while away from the camera, blink an eye, blink the other eye, then stick your tongue out. It'll spot em all. (on mine anyway)
I might as well release source on this when im done playing :)