Images are both maps of continuous physical phenomena and discrete mathematical objects. While Shannon established the fundamental relationship between physical and mathematical images over half a century ago, considerable further progress in understanding this relationship has been achieved in the past quarter century through the development of wavelets and compressive measurement. This talk reviews simple physical models for the physical to mathematical transformation and discusses strategies for coding the physical interface to increase measurement efficiency. We specifically discuss novel sampling strategies for x-ray tomography, diffraction tomography and focal imaging.