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They are typically referred to as Porter Duff blend modes, so I assume that these algorithms were invented mainly by those guys. (by Thomas Porter and Tom Duff)

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This set me on an interesting trail. I haven’t found anything yet that links Porter and Duff to the modern blend modes as we know them, but I did find this 1984 SIGGRAPH paper they authored that appears to have laid much of the groundwork! https://graphics.pixar.com/library/Compositing/paper.pdf

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/

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/

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