Custom blend mode? A=max(As, Ad)?

[Jona]

I'm trying to achieve the following blend mode:

A=max(As, Ad)

I did achieve this using lighten blend mode and then applying a color filter to swap one of the color channel as the alpha channel. However, this did loose the alpha channel which holds the anti-alias of the shape drawn.

How could I achieve such blend mode? How could I build my own blend mode?

Any help or direction would be greatly appreciated!

- Jona

[John Stiles]

Sorry for the late reply, but if you are still looking for a solution here, Runtime Effects now supports authoring a custom blend function. You can write a simple runtime blend function which returns max(src, dst) and apply it to your SkPaint.

Check out SkRuntimeEffect::MakeBlender().

This tech is very new (it didn't exist yet in April when you posted this!) but it should be a very good fit for this.