1. A snapshot spectral imager for obtaining spectral images of a source object, comprising: a) an imaging lens; b) a dispersed image sensor; and c) a restricted isometry property (RIP) diffuser inserted in an optical path between the source object and the dispersed image sensor, wherein the snapshot spectral imager is configured to obtain at the dispersed image sensor a dispersed image formed through the imaging lens and the RIP diffuser, and wherein the snapshot spectral imager is further configured to process the dispersed image to provide a plurality of spectral images of the source object.