> You're talking about nearest-neighbour resampling. That will cause jagged edges, it > won't get you smooth enlargement.
There's only two ways to "increase resolution":
1) double pixels - results in "jaggies" and is limited to certain size multiples 2) some other method that averages pixels to create new pixels - results in "blurries"
The second method is what is most programs use along with some kind of filter like "Unsharp Mask"