Many shapes can be represented using a surprisingly small number of binary pixels. For n pixels, there are of course 2^n different patterns (although a huge proportion of these are not perceived as shapes).
Using an array of only a few hundred pixels allows eg the face of someone famous to be recognised.
It should be possible to adapt existing projected keyboard technology to allow projection of an array of several hundred ‘pixels’ and thus form a general purpose touch screen capable of displaying a huge number of ‘clickable’ shapes.
An image displayed by this system could sense which ‘key’ was being pressed and substitute a zoomed image of the local region in question. In this way, all public touch screens, for accessing services or navigating plans or maps, could be replaced with projectors generating interactive, vandalproof content at minimal cost.