If you are mapping the lines where each pixel has resistance and capacitance (presumably quite small values) could you add a new pixel type with editable resistance / capacitance and hide it behind a graphic of the schematic representation (i.e. the zigzag of a resistor like --\/\/\-- or capacitor like --|(-- ?

Your current algorithm would need to be able to accept a wider range of values but it seems like it would work from a math standpoint.