OpenCV project development practice--Eigenface application of principal component analysis (PCA) (with C++/Python implementation source code)

What is principal component analysis?

This is a prerequisite for understanding this article.

Figure 1: Showing the main components of 2D data (red dots) using blue and green lines.

As a quick refresher, we learned that the first principal component is the direction of maximum variance in the data. The second principal component is the direction of maximum variance in space that is perpendicular (orthogonal) to the first principal component, and so on. The first and second principal component red points (2D data) are shown using blue and green lines.