The mix-blend-mode CSS property controls the blending of an element with the background. I want the colour of my canvas element to be added to the colour of the background.
ABA + BSurprisingly, there is no add option. The option screen does 1-(1-A)(1-B) which simplifies to A + B + A(-B).
There seems to also be plus-lighter. However, this option seems pretty recent and is not supported in all browsers e.g. IE.
Is there a universally supported way to do a simple additive blend of a canvas with the background html element?
As far as I know, there are no options capable of doing what you want that are globally accepted, but plus-lighter is fortunately supported across several browsers.
Perhaps your best option would be to write a custom method that takes both colors and adds them. This question could be of great help.