Found this powerhouse store of plug-in for Photoshop with a good previewing system to see what each does:
How many times did someone flatten an image and they wanted their transparent layer or scetchwork back?
I am surprised Photoshop doesn't include this one, Whiteout & Blackout (Screen mode subtract or layer setting with a Subtract "threshold", Photoshop lack operations that works in screen mode or would process towards transparency, But just now they make real powerful tools fall into the wrong hands. Mwahahahaha!!)
I would like to see a top papparazzi agent's plug in directory. Haha!