blend

Composites a source color over a backdrop with a blend mode, as the browser does for mix-blend-mode (W3C Compositing and Blending Level 1, source-over). Both colors are straight (non-premultiplied); the maths run in premultiplied space and the result is straight again, each channel and the alpha rounded to the nearest 8-bit value.

Import

use helpers4::color::blend;

Cargo feature color (enabled by default). To compile only this module:

cargo add helpers4 --no-default-features --features color

or in Cargo.toml:

[dependencies]
helpers4 = { version = "0.0.11", default-features = false, features = ["color"] }

Signature

pub fn blend(backdrop: Rgba, source: Rgba, mode: BlendMode) -> Rgba

Parameters

Parameter	Type	Description
backdrop	Rgba	The color underneath.
source	Rgba	The color painted over it.
mode	BlendMode	The blend mode; BlendMode::Normal is a plain alpha composite.

Returns

Rgba — The straight result. Transparent black when both colors are fully transparent.

Examples

use helpers4::color::{blend, BlendMode, Rgba};

let red = Rgba::new(255, 0, 0, 255);
let half_blue = Rgba::new(0, 0, 255, 128);
assert_eq!(blend(red, half_blue, BlendMode::Normal), Rgba::new(127, 0, 128, 255));

let orange = Rgba::new(200, 100, 50, 255);
let gray = Rgba::new(100, 100, 100, 255);
assert_eq!(blend(orange, gray, BlendMode::Multiply), Rgba::new(78, 39, 20, 255));

Source

src/color/blend.rs