Compositing elements with a colored background, or how to invert almost any comp operation.

Alright, that’s a long title, but that’s the shortest I could come up with to describe this tutorial. It’s not rare that someone, somewhere, provides us with an element (logo, UI, motion graphics, precomp, anything really) with a nice alpha, but with a white or colored background.  Of course it’s not ideal, but that’s nothing [...]