RustでHSLからRGBに変換する関数

hsl_to_rgb.rs

fn hsl_to_rgb(h: f64, s: f64, l: f64) -> (u8, u8, u8) {
    let (mut r, mut g, mut b) = (l, l, l);
    if s != 0.0 {
        let hue2rgb = |p: f64, q: f64, t: f64| -> f64 {
            let mut t = t;
            if t < 0.0 { t += 1.0; }
            if t > 1.0 { t -= 1.0; }
            if t < 1.0 / 6.0 { return p + (q - p) * 6.0 * t; }
            if t < 1.0 / 2.0 { return q; }
            if t < 2.0 / 3.0 { return p + (q - p) * (2.0 / 3.0 - t) * 6.0; }
            p
        };
        let q = if l < 0.5 { l * (1.0 + s) } else { l + s - l * s };
        let p = 2.0 * l - q;
        r = hue2rgb(p, q, h + 1.0 / 3.0);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1.0 / 3.0);
    }
    ((r * 255.0).round() as u8, (g * 255.0).round() as u8, (b * 255.0).round() as u8)
}