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Comment by mortenjorck | Hacker News Reader

This is a great technical explainer on the blend modes, but it makes me want to go deeper: Where did the canonical 18 blending algorithms that we take for granted today originate? Was it a brainstorming session between John and Thomas Knoll in 1992? A paper by Ed Catmull in 1979? Did Adobe invent them, or merely popularize them?

Somewhere, there’s an oral history of blending modes waiting to be told, and I can’t wait to read it.

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I wouldn't call this list "canonical", rather it's the list of agreed blend modes set out in the W3C Compositing and Blending Level 2 specification[1][3]. Other products have different views on what sort of blend modes to include - for instance Photoshop defines 29 of them[2], compared to the 16 defined in the W3C spec.

Concerning the Hue, Saturation, Color and Luminosity blends - I've been wondering if there would be anything to gain from creating similar types of blend from colors defined using the LCH and/or LAB color spaces ...?

[1] - W3C spec - https://drafts.fxtf.org/compositing/#blending

[2] - Normal, Dissolve, Behind, Clear, Darken, Multiply, Color Burn, Linear Burn, Lighten, Screen, Color Dodge, Linear Dodge (Add), Overlay, Soft Light, Hard Light, Vivid Light, Linear Light, Pin Light, Hard Mix, Difference, Exclusion, Subtract, Divide, Hue, Saturation, Color, Luminosity, Lighter Color, Darker Color - see https://helpx.adobe.com/uk/photoshop/using/blending-modes.ht...

[3] - I spent far too long on the W3C spec page last Christmas when I built a blend filter for my canvas library (maths is not my strongest talent); even now I'm not convinced that I got all the calculations right - https://scrawl-v8.rikweb.org.uk/demo/filters-102.html

As far as I know, they were an Adobe invention. Might not seem like it now, but Adobe did at one time have a pretty massive and respectable graphics R&D team who invented so many things that we take as standard now. The formulas were reverse-engineered elsewhere, but not perfectly (Macromedia Fireworks and GIMP's blend modes did not behave the same way). As far as I know, the exact formulas were first documented in the PDF Specification v1.4 by Adobe: https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandard... . At the time, this was an ISO specification and not freely available. Also, the formulas for Color Burn and Color Dodge in this specification have some bugs which don't match Adobe products. These formulas have since been copied into the SVG standard (which Adobe co-authored), and the CSS blend mode standard (which Adobe co-authored), where the bugs are now fixed.

Porter-Duff compositing was more of a general theory for compositing A on top of B with a mask C, and the operators defined in their paper were the 3-way truth table of those bits. It only defines coverage, not the underlying color.

https://en.wikipedia.org/wiki/Darkroom_manipulation

https://en.wikipedia.org/wiki/Dodging_and_burning

That's only a small part of the available blend modes. I've always wondered how the digital versions of dodge and burn compare to the darkroom versions.

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)

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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