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