Easy way to resize dynamically loaded JPEG?

I’m loading an external image and resizing it proportionally once it’s loaded, but I need to know if there’s a more efficient/effective way to do it. Right now I’ve got:

loadMovie("image1.jpg", mc1);
onEnterFrame = function() {
    percent1 = mc1.getBytesLoaded()/mc.getBytesTotal();
    if (percent1 == 1) {
        ratio = mc1._width/mc1._height;
        mc1._width = 100*ratio;
        mc1._height = 100;

The image kinda jumps around as it’s loading… seems like a pretty tacky way of doing it.

Any ideas?