run into a bit of a wall that I can't seem to find an answer for elsewhere.
Bog standard "This is a health bar, extend this image over it to mask it based on current hp".
Bit of a pain working with non-rectangular/detailed health bars since you can just set the origin to the end and the adjust the width based on health, sadly this one needs a specific masked shape.
Image from the usual flash method of what i'm talking about if I wasn't clear:
<img src="https://imagizer.imageshack.us/v2/1220x645q90/23/jwxk.png" border="0" />
So yeah, how do I Opacity Mask?