... since zooming works with scaling up bitmaps, it is most likely not what you want.
Hello Sven; is the scale factor strictly 2^n where n is an integer? Is that why you say "not what you want"?
The gestural zooming on an iPad works well. I wonder what scale factors are used and how the scaling is implemented. A2 might benefit from some of the techniques.
Regards, ... Peter Easthope