Yes. Mirrors are more truthful than pictures because pictures can be edited with stuff like Photoshop, and many cameras don't show the exact color of things (my camera always puts a pink shade on everything).
However, the image you see in the mirror can be distorted by your own view of yourself. Someone before me answered that other people's eyes are more truthful, but their vision of you can be clouded by their own judgement. Really, I think there is no way to know exactly what you look like unless you look in the mirror without judging yourself.