Comment by pornel

I'm saying "digital images" are captured by and created for hardware that has the "little squares". This defines what their pixels really are. Pixels in these digital images actually represent discrete units, and not infinitesimal samples of waveforms.

Since the pixels never were a waveform, never were sampled from such signal (even light in camera sensors isn't sampled along these axis), and don't get displayed as a 2D waveform, the pixels-as-points model from the article at the top of this thread is just an arbitrary abstract model, but it's not an accurate representation of what pixels are.