Yes, it does look like a Photoshop filter, rather than a painting, although I do see a resemblence to how Roxanne would probably look in real life.
What I don't see, though, is how people can compare Roxanne to Lois Lane from the Superman universe. Lois was always shown as a glasses-wearing, long-haired, and somewhat nerdish newspaper reporter, who really didn't have to worry about her looks because she never had to appear on camera, unlike Roxanne. Lois also had the hots for the superHERO, while pointedly ignoring HIS nerdish alter-ego, Clark Kent. That's the opposite of Roxanne Ritchi, who was not impressed by the flamboyant superhero Metro Man, but was secretly attracted to and later became genuinely involved with his rival, the supervillain Megamind. Roxanne also knew that unlike Lois Lane, she was never in any real distress or danger at all from said supervillain, so she never showed fear or acted helpless. Even if Meto Man hadn't shown up to "rescue" her Roxanne knew that she was in no danger and after flirting/bantering with her captor and Minion, she'd be taken home safe and sound.