OK, I'm being pedantic.
Enlarge Images Without Quality Loss doesnt exist as I'm sure you're fully aware
Actually, enlargement is perfect 100% fidelity. No information is lost when enlarging, at least for a naive algorithm. If you do straight scaling, you will be able to increase the resolution and then decrease it to the exact original size, and the output will be identical to the input. (some interpolation algorithms may, however, introduce changes)
I suppose that what you meant is that the quality can't exceed 100% in that it can't add detail that wasn't in the original (smaller) image. Various algorithms can interpolate to make the image appear
to be more detailed, but this is just a trick of perception.
On the other side of the coin, it's shrinking
image resolution that is necessarily lossy.
And btw, I'm a fan of Qimage, I use it all the time for printing. Keep in mind that it's useful not only for boosting (perceived) resolution, but also for applying color and broghtness corrections, for example.