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. For example, when the rendered composite image is subjected to illumination by one of the narrow band illuminants for which a source image was encoded, the source image becomes visually detectable by an observer.