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Per-Pixel Collision Detection is something that you should not be thinking on making because it uses way to many resources if you are going to use the CPU, you could use the GPU but I can't help you there, I have not idea on how to.
Have you seen the physics module ? People usualy say that it's not what you want to use when you are making a side-scroller games but it's actually a really good tool for all kinds of physics. See Concerned Joe for exemple, it uses Box2D (physics module)

Maybe off-topic, but i'll share this.

Yep, that loops thought all pixels on the sprite so it'll make things really slow.