1. An image forming medium, comprising a substrate; and an imaging layer coated on or impregnated into said substrate, wherein the imaging layer comprises: a photobase generator, a coupling agent, and a photoacid generator, wherein irradiation of the imaging layer with light of a first wavelength causes said photobase generator to generate a base that reacts with the coupling agent to produce an extended conjugation that forms an image, and irradiation of the imaging layer with light of a second wavelength causes said photoacid generator to generate an acid that reacts with the extended conjugation to reverse formation of the extended conjugation to erase the image.