A grey and white table titled: Formulas for Photoshop blending modes The subtitle says: Originally created by Rogelio Bernal Andreo "While some of the formulas are precisely what Photoshop does, others are just an approximated guess." What follows are rows of blend modes, including their forumlas, their commutavity, and additional info. A link to the full webpage with machine readable text is available at: https://web.archive.org/web/20210526073530/http://www.deepskycolors.com/archive/2010/04/21/formulas-for-Photoshop-blending-modes.html This link will also be posted in the replies.
Shader Artists!
Here's a super handy reference for the formulas behind Photoshop's blending modesβ¨