I'm well aware that this is borderline off-topic, but does anyone know how authors include (apparently) hand-drawn pictures in their books, such as this one from a programming textbook:
Such pictures seem to be too perfect to be made by hand, and show no sign of having been scanned. But I cannot imagine doing this with TikZ or Inkscape or any other drawing tool.

\includegraphics? – Bernard Jun 27 '17 at 17:01