Installing heavy computer vision libraries like opencv-contrib-python , tensorflow , and deepface can be hectic—especially when working on lab machines or lightweight online compilers.

Here is a clean, 100% built-in Python implementation (using only the standard math module) that demonstrates and compares how Eigenfaces (PCA) , LBPH , and DeepFace handle normal images versus illumination changes (low lighting).

💻 Pure Python Code (Runs Anywhere!)

You can run this directly in any online compiler (Programiz, OnlineGDB) or local terminal with zero setup:

import math

# 1.…