pub(crate) fn is_light(bg: (u8, u8, u8)) -> bool {    let (r, g, b) = bg;    let y = 0.299 * r as f32 + 0.587 * g as f32 + 0.114 * b as f32;    y > 128.0}pub(crate) fn blend(fg: (u8, u8, u8), bg: (u8, u8, u8), alpha: f32) -> (u8, u8, u8) {    let r = (fg.0 as f32 * alpha + bg.0 as f32 * (1.0 - alpha)) as u8;    let g = (fg.1 as f32 * alpha + bg.1 as f32 * (1.0 - alpha)) as u8;    let b = (fg.2 as f32 * alpha + bg.2 as f32 * (1.0 - alpha)) as u8;    (r, g, b)}/// Returns the perceptual color distance between two RGB colors./// Uses the CIE76 formula (Euclidean distance in Lab space approximation).pub(crate) fn perceptual_distance(a: (u8, u8, u8), b: (u8, u8, u8)) -> f32 {    // Convert sRGB to linear RGB    fn srgb_to_linear(c: u8) -> f32 {        let c = c as f32 / 255.0;        if c <= 0.04045 {            c / 12.92        } else {            ((c + 0.055) / 1.055).powf(2.4)        }    }    // Convert RGB to XYZ    fn rgb_to_xyz(r: u8, g: u8, b: u8) -> (f32, f32, f32) {        let r = srgb_to_linear(r);        let g = srgb_to_linear(g);        let b = srgb_to_linear(b);        let x = r * 0.4124 + g * 0.3576 + b * 0.1805;        let y = r * 0.2126 + g * 0.7152 + b * 0.0722;        let z = r * 0.0193 + g * 0.1192 + b * 0.9505;        (x, y, z)    }    // Convert XYZ to Lab    fn xyz_to_lab(x: f32, y: f32, z: f32) -> (f32, f32, f32) {        // D65 reference white        let xr = x / 0.95047;        let yr = y / 1.00000;        let zr = z / 1.08883;        fn f(t: f32) -> f32 {            if t > 0.008856 {                t.powf(1.0 / 3.0)            } else {                7.787 * t + 16.0 / 116.0            }        }        let fx = f(xr);        let fy = f(yr);        let fz = f(zr);        let l = 116.0 * fy - 16.0;        let a = 500.0 * (fx - fy);        let b = 200.0 * (fy - fz);        (l, a, b)    }    let (x1, y1, z1) = rgb_to_xyz(a.0, a.1, a.2);    let (x2, y2, z2) = rgb_to_xyz(b.0, b.1, b.2);    let (l1, a1, b1) = xyz_to_lab(x1, y1, z1);    let (l2, a2, b2) = xyz_to_lab(x2, y2, z2);    let dl = l1 - l2;    let da = a1 - a2;    let db = b1 - b2;    (dl * dl + da * da + db * db).sqrt()}