I don't know the history, but there is supposedly a fixed set of Porter Duff blend modes, specific algorithms. For example, this C++ library: > Blend2D support

I don't know the history, but there is supposedly a fixed set of Porter Duff blend modes, specific algorithms. For example, this C++ library: > Blend2D supports all Porter & Duff compositing operators https://blend2d.com/ https://blend2d.com/ Also, the link shared by one of the sibling comments can be searched for "Porter" to see how they are referenced: https://drafts.fxtf.org/compositing/ https://drafts.fxtf.org/compositing/