AniRenderer: cache viewport and change Math.floor to double bitwise not

Math.floor is slower than double bitwise not.
bypassing function calls in AniRenderer to try and increase speed

Although function calls have an overhead, removing a bunch here
did not appear to give a change in performance. I'll be working on
taking things in this direction anyway, because this is a critical
loop to optimize.

Hopefully pre-rendering sprites will give a performance difference.