Gentlemen, I really didn't intend to get on your nerves. Maybe I sounded bitter after seeing my topic turned into a grammar war
You're right, opening the full-size pictures takes more than a single click. I've now done what I should have since the beginning : isolated the compass from each screenshot. Was quicker than I thought, and everything sure becomes clearer. Please take a look a that first post again.
I have not counted pixels, but to me the compass still looks either "ok" or "squashed", not "more or less squashed". Anyway, Marty enlightened me on the causes of the problem, which is all I wanted. So it's nothing new, alright. Sorry for the misunderstandings & thanks for bearing with me !