It is just a normal figure (basically a grid of squares filled with colours in some simple pattern). It should not take long to compile.
I suspect the author actually didn’t know how to draw in LaTeX, so he asked a colleague, who happened to also draw in LaTeX…
Maybe they tried to bring the compilation time down and were not aware that they could insert them as vector graphics?
I really don't understand how.
My professor's notes have a lot of figures. The note is in LaTeX, the figures are also drawn in LaTeX (or at least the font there is Computer Modern), but for some reasons the figures are added as screenshots to the notes.
Package of the day: [cleveref](https://ctan.org/pkg/cleveref)
"Arara is a cross-platform automation tool that's specially designed for TeX. It's included in a standard distribution, so there's no need to install anything additional. It's most effectively understood as a means to record the compilation instructions in the TeX file itself:"
sure, you could as well run LaTeX once and afterwards another tool/script to separate the document (possibly, using LaTeX and `pdfpages`, but that would accumulate three LaTeX runs)
Quick poll: What are your favourite (professional or simply beautiful looking) *sans* serif fonts? (you can check the [font catalogue](https://tug.org/FontCatalogue/sansseriffonts.html) if you want to)