If you rasterize them anyway, I'd suggest generating images of different size and using them at certain
scalings. See
http://megazine.mightypirates.de/wiki/index.php/Adaptive_ZoomJust redrawing the images would not help by itself, because the size doesn't change in the local coordinate
system of the images. So I'd have to raster them into a rather big bitmap which I'd scale down again, which
would then be upscaled due to the zoom of the pages, which in the end would most likely result in not so
nice interpolation.
If you want to give it a try yourself, feel free to do so, though. You'd have to change the Img class for that,
and use the scale change events of the MegaZine instance.