In my answer below:
I used a picture by quanta from another answer.
I gave the link and the name, so I think that this is fine, but I want to check if everyone thinks that this is good practice.
Both the citation aspect and the practical aspect (can quanta change the image that I just linked or is it fixed once it is uploaded?) are of interest.
It is also true that my answer would be better served by a new picture without the little black arrows and with $a$ and $b$ not coprime, and you are welcome to comment on my laziness or just make a new picture for my post, but I would like to also have comments on the best practice regardless of this particular aspect.