Color Contrast

contrast.py

from coloraide.contrast import ColorContrast

class Weber(ColorContrast):
    """Weber contrast."""

    NAME = "weber"

    @classmethod
    def contrast(cls, color1, color2, **kwargs):
        """Contrast."""

        lum1 = color1.luminance()
        lum2 = color2.luminance()

        if lum1 > lum2:
            lum2, lum1 = lum1, lum2

        if lum1 == 0:
            return 0

        return (lum2 - lum1) / lum1


class Michelson(ColorContrast):
    """Michelson contrast."""

    NAME = "michelson"

    @classmethod
    def contrast(cls, color1, color2, **kwargs):
        """Contrast."""

        lum1 = color1.luminance()
        lum2 = color2.luminance()

        if lum1 > lum2:
            lum2, lum1 = lum1, lum2

        d = lum2 + lum1

        if d == 0:
            return 0

        return (lum2 - lum1) / d

class Color2(Color): ...
Color2.register([Weber, Michelson])

Color2('red').contrast('blue')
Color2('red').contrast('blue', method="weber")
Color2('red').contrast('blue', method="michelson")