withBackground method
Resolves against a background color.
If background
is opaque, the returned color will also be opaque.
Implementation
Color withBackground(Color background) => alpha == 1
? this
: Color.rgba(
_lerpNum(background.red, red, alpha).toInt(),
_lerpNum(background.green, green, alpha).toInt(),
_lerpNum(background.blue, blue, alpha).toInt(),
_lerpNum(background.alpha, 1, alpha));