Function alphaComp

blend/blend.go:379–389

alphaComp returns a new color after compositing the two colors based on the foreground's alpha channel.

(bg, fg fcolor.RGBAF64)

// alphaComp returns a new color after compositing the two colors
// based on the foreground's alpha channel.
func alphaComp(bg, fg fcolor.RGBAF64) fcolor.RGBAF64 {
	fg.Clamp()
	fga := fg.A

	r := (fg.R * fga / 1) + ((1 - fga) * bg.R / 1)
	g := (fg.G * fga / 1) + ((1 - fga) * bg.G / 1)
	b := (fg.B * fga / 1) + ((1 - fga) * bg.B / 1)
	a := bg.A + fga

	return fcolor.RGBAF64{R: r, G: g, B: b, A: a}
}