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 on a substrate, 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. At least one of the source images includes image content in the form of a textured image. When the rendered composite image is subjected to illumination by one of the narrow band illuminants for which a source image was encoded, the textured image in the recovered source image becomes visually detectable.