drawToBitmap is slow, there’s really no way to improve it. You write your animation consists of a PNG sequence; an obvious way is to keep them in memory as
BitmapData then use
getPixelon them to test for collisions.
That will get you single point collisions, such as for touch or with a point projectile. For more complex collisions between two arbitrary sprites there is no easy way; for that you need to model your sprites someway, such as boxes or circles, or collections of them.