A Simple Image Model

A 2D light intensity function f(x, y)

•   f(x, y) = i(x, y) r(x, y)

i(x, y): illumination component, i(x, y) > 0
r(x, y): reflectance component, (0, 1)

where r(x, y) = 0: Total Absorption
r(x, y) = 1: Total Reflectance

In theory: f(x, y) > 0
In practice: f(x, y) falls into [Lmin, Lmax] = [iminrmin,imaxrmax]

The physical image is a continuous voltage waveform whose 
amplitude and spatial behavior are related to the physical 
phenomenon being sensed.