Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering at least one of the encoded source images from the rendered composite image such that the recovered source image is made distinguishable. A noise component is introduced in the encoding of the plurality of source images so as to mask at least one of the source images during spectral demultiplexing.