"Visualization of the Digits of π – A Randomness Test" D. Bailey, J. Borwein In: Experimental Mathematics in Action (2007) Why: They map digits of Pi to color or grayscale images to visually assess randomness.

If you are working with imaging (Pi Camera V2 or HQ), there is no “Pi7” yet. But if you meant Pi Camera image processing :

In coherent diffraction imaging, stands for Ptychographic Iterative Engine .