If it is a resistive matrix, you can connect a set of wires to rows from one and and another set of wires to cross-row from the other end. 256 wires from one end, and 256 wires from other end will let you measure 65536 resistor points. 512 wires is quite manageable. All you need is to connect ground to exactly one wire from one end and positive voltage to exactly one wire at the other end. This will push all the current through only one resistor and you can measure it. If you can control capacitance, it may be feasible.