That extension is one way to do it. You need to do it using the classic Flash API, as only there can you get individual pixels, to test their transparency to see whether touching should trigger. So load your art as BitmapData, create Textures from them for drawing, but keep the BitmapData around for threshold queries.
You might want to look at this recent thread:
Although on a different topic it concerns many of the same issues, of wanting to get information from a piece of art, so using the classic API, but drawing with Starling.