Function contrast_ratio 

pub fn contrast_ratio<T>(luma1: T, luma2: T) -> T
where
    T: Real + Arithmetics + PartialCmp,
    <T as HasBoolMask>::Mask: LazySelect<T>,

👎Deprecated since 0.7.2:

replaced by LinLuma::relative_contrast, via Wcag21RelativeContrast

Calculate the ratio between two luma values.