If "shrink" then why not "scale up"? Or simply just: "resize" [with at least an option of a fixed ratio of 1:1]
Somebody might want to make them bigger, because how a given player shows them. Even if that would mean "pixelizing" them [but small increases like to 120% of original are pretty much of the same quality / readability]
And with that would nicely go along implementation of these features: