Can the iPad detect the shape of a contact on its screen using objective C?

For example, could the iPad or iPhone accurately detect the difference between conductive pieces of plastic i开发者_开发技巧n the following shapes using Objective C...

http://i52.tinypic.com/307rtar.gif

http://i51.tinypic.com/23k83tj.gif

http://i55.tinypic.com/nybc6e.gif

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If the above can't work is it possible to detect the number of points touching the screen?

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As Mr. Weinberg notes, you can't do it with FLAT touches. But, if you put small nubs on the pieces you could use them to stand in for a multi-touch (ie one small nub at each vertex). You could then figure out the shape of the convex hull these points would create.

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The hardware itself might have the ability, but as far as the API we get, no, you wouldn't be able to tell those apart.

To take into account your edit. Yes, you can detect up to 11 discrete touches on the device. From there you should be able to figure out which shape is what pretty easily, but once you have more than 11 contact points on the screen all bets are off.