Primitive contrast-ratio helpers.

The helpers here are intentionally small utility calculations. They do not guarantee full compliance outcomes by themselves.

Examples

use use_contrast::{
    ContrastLevel, RgbColor, classify_normal_text, contrast_ratio, passes_normal_text_aaa,
    relative_luminance,
};

let black = RgbColor {
    red: 0,
    green: 0,
    blue: 0,
};
let white = RgbColor {
    red: 255,
    green: 255,
    blue: 255,
};
let ratio = contrast_ratio(black, white);

assert!(relative_luminance(white) > relative_luminance(black));
assert!((ratio - 21.0).abs() < 1.0e-12);
assert!(passes_normal_text_aaa(ratio));
assert_eq!(classify_normal_text(ratio).unwrap(), ContrastLevel::AAA);