for both directions I would say a competent artist. Clever algorithms get you some of the way, but you will still need someone with good sense to edit the resu

for both directions I would say a competent artist. Clever algorithms get you some of the way, but you will still need someone with good sense to edit the result to get something usable, which is going to cost you in either time or money. Downsizing isn't so bad now because of higher DPI displays (e.g. font hinting is obsolete now) but previously designers would need to make individual icons in a number of sizes removing elements as necessary.