Low quality when rescaling bitmaps?

I have a problem with rescaling bitmap images in Flash. They usually don’t look good at all.

I have higher resolution bitmaps images I want to downscale in Flash. Here is a comparison between an image downscaled in Flash (left) and Photoshop (right). I realize I won’t get quite the quality of Photoshop, but there must be some trick for improving it?

I also get wierd behavior in Flash regarding this issue. Some images sometimes (?!) look very good, pretty much like the one to the right, without dots and distorted lines. But most don’t look good. How to fix this?