Additive blending with alpha channel
3c1u opened this issue · comments
Hi, I'm using Piston for my game development and I thought that adding a blending mode such as "Screen" like in Photoshop will be convenient.
I've tried Blend::Add and it was disappointing because it doesn't handle alpha channel, whereas lighter mode in CanvasRenderingContext2D::globalCompositeOperation (JavaScript/HTML5 Canvas) does. I modified the graphics crate (3c1u/gfx_graphics and 3c1u/graphics) to replicate this as Blend::Screen.
I drew rgba(0, 0, 255, 0.5) (left) and rgba(0, 0, 255, 1.0) (right) over rgba(255, 0, 0, 1.0) and the following images are the results.
top: lighter (HTML5 Canvas), bottom: Blend::Screen (modified Piston)
top: lighter (HTML5 Canvas), bottom: Blend::Add (unmodified Piston)
Is it possible to add this feature to Piston, as well as other graphic backends?
Yes! Can you make a PR?
Renamed to Blend::Lighter (because it was actually different from "Screen" from Photoshop) and made a PR (PistonDevelopers/graphics#1131). Thank you.