Improve contrast of built-in themes by leveraging Oklch
This commit is contained in:
Héctor Ramón Jiménez
parent
148fc77b8f
commit
0857eb3bde
28 changed files with 124 additions and 116 deletions
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@ -28,7 +28,7 @@ impl Palette {
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text: Color::BLACK,
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primary: color!(0x5865F2),
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success: color!(0x12664f),
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warning: color!(0xffc14e),
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warning: color!(0xb77e33),
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danger: color!(0xc3423f),
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};
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@ -453,9 +453,13 @@ pub struct Background {
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/// The weakest version of the base background color.
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pub weakest: Pair,
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/// A weaker version of the base background color.
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pub weaker: Pair,
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/// A weak version of the base background color.
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pub weak: Pair,
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/// A stronger version of the base background color.
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/// A strong version of the base background color.
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pub strong: Pair,
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/// A stronger version of the base background color.
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pub stronger: Pair,
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/// The strongest version of the base background color.
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pub strongest: Pair,
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}
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@ -464,15 +468,19 @@ impl Background {
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/// Generates a set of [`Background`] colors from the base and text colors.
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pub fn new(base: Color, text: Color) -> Self {
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let weakest = deviate(base, 0.03);
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let weak = muted(deviate(base, 0.1));
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let strong = muted(deviate(base, 0.2));
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let strongest = muted(deviate(base, 0.3));
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let weaker = deviate(base, 0.07);
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let weak = deviate(base, 0.1);
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let strong = deviate(base, 0.15);
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let stronger = deviate(base, 0.175);
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let strongest = deviate(base, 0.20);
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Self {
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base: Pair::new(base, text),
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weakest: Pair::new(weakest, text),
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weaker: Pair::new(weaker, text),
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weak: Pair::new(weak, text),
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strong: Pair::new(strong, text),
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stronger: Pair::new(stronger, text),
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strongest: Pair::new(strongest, text),
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}
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}
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@ -517,9 +525,11 @@ pub struct Secondary {
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impl Secondary {
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/// Generates a set of [`Secondary`] colors from the base and text colors.
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pub fn generate(base: Color, text: Color) -> Self {
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let base = mix(base, text, 0.2);
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let weak = mix(base, text, 0.1);
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let strong = mix(base, text, 0.3);
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let bump = if is_dark(base) { 0.0 } else { 0.01 };
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let weak = mix(deviate(base, 0.1 + bump), text, 0.4);
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let base = mix(deviate(base, 0.3 + bump), text, 0.4);
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let strong = mix(deviate(base, 0.5 + bump), text, 0.4);
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Self {
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base: Pair::new(base, text),
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@ -604,53 +614,51 @@ impl Danger {
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}
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}
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struct Hsl {
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h: f32,
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s: f32,
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struct Oklch {
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l: f32,
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c: f32,
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h: f32,
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a: f32,
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}
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fn darken(color: Color, amount: f32) -> Color {
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let mut hsl = to_hsl(color);
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let mut oklch = to_oklch(color);
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hsl.l = if hsl.l - amount < 0.0 {
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// We try to bump the chroma a bit for more colorful palettes
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oklch.c *= 1.0 + 2.0 * amount / oklch.l.max(0.05);
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oklch.l = if oklch.l - amount < 0.0 {
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0.0
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} else {
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hsl.l - amount
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oklch.l - amount
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};
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from_hsl(hsl)
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from_oklch(oklch)
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}
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fn lighten(color: Color, amount: f32) -> Color {
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let mut hsl = to_hsl(color);
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let mut oklch = to_oklch(color);
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hsl.l = if hsl.l + amount > 1.0 {
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// We try to bump the chroma a bit for more colorful palettes
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oklch.c *= 1.0 + 2.0 * amount / oklch.l.max(0.05);
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oklch.l = if oklch.l + amount > 1.0 {
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1.0
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} else {
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hsl.l + amount
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oklch.l + amount
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};
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from_hsl(hsl)
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from_oklch(oklch)
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}
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fn deviate(color: Color, amount: f32) -> Color {
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if is_dark(color) {
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lighten(color, amount)
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} else {
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darken(color, amount * 0.8)
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darken(color, amount)
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}
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}
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fn muted(color: Color) -> Color {
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let mut hsl = to_hsl(color);
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hsl.s = hsl.s.min(0.5);
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from_hsl(hsl)
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}
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fn mix(a: Color, b: Color, factor: f32) -> Color {
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let b_amount = factor.clamp(0.0, 1.0);
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let a_amount = 1.0 - b_amount;
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@ -680,6 +688,12 @@ fn readable(background: Color, text: Color) -> Color {
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return candidate;
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}
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let candidate = improve(text, 0.2);
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if is_readable(background, candidate) {
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return candidate;
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}
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let white_contrast = relative_contrast(background, Color::WHITE);
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let black_contrast = relative_contrast(background, Color::BLACK);
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@ -691,11 +705,11 @@ fn readable(background: Color, text: Color) -> Color {
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}
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fn is_dark(color: Color) -> bool {
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to_hsl(color).l < 0.6
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to_oklch(color).l < 0.6
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}
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fn is_readable(a: Color, b: Color) -> bool {
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relative_contrast(a, b) >= 7.0
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relative_contrast(a, b) >= 6.0
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}
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// https://www.w3.org/TR/WCAG21/#dfn-contrast-ratio
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@ -711,65 +725,57 @@ fn relative_luminance(color: Color) -> f32 {
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0.2126 * linear[0] + 0.7152 * linear[1] + 0.0722 * linear[2]
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}
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// https://en.wikipedia.org/wiki/HSL_and_HSV#From_RGB
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fn to_hsl(color: Color) -> Hsl {
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let x_max = color.r.max(color.g).max(color.b);
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let x_min = color.r.min(color.g).min(color.b);
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let c = x_max - x_min;
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let l = x_max.midpoint(x_min);
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// https://en.wikipedia.org/wiki/Oklab_color_space#Conversions_between_color_spaces
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fn to_oklch(color: Color) -> Oklch {
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let [r, g, b, alpha] = color.into_linear();
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let h = if c == 0.0 {
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0.0
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} else if x_max == color.r {
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60.0 * ((color.g - color.b) / c).rem_euclid(6.0)
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} else if x_max == color.g {
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60.0 * (((color.b - color.r) / c) + 2.0)
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} else {
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// x_max == color.b
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60.0 * (((color.r - color.g) / c) + 4.0)
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};
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// linear RGB → LMS
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let l = 0.41222146 * r + 0.53633255 * g + 0.051445995 * b;
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let m = 0.2119035 * r + 0.6806995 * g + 0.10739696 * b;
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let s = 0.08830246 * r + 0.28171885 * g + 0.6299787 * b;
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let s = if l == 0.0 || l == 1.0 {
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0.0
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} else {
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(x_max - l) / l.min(1.0 - l)
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};
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// Nonlinear transform (cube root)
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let l_ = l.cbrt();
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let m_ = m.cbrt();
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let s_ = s.cbrt();
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Hsl {
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h,
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s,
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l,
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a: color.a,
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}
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// LMS → Oklab
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let l = 0.21045426 * l_ + 0.7936178 * m_ - 0.004072047 * s_;
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let a = 1.9779985 * l_ - 2.4285922 * m_ + 0.4505937 * s_;
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let b = 0.025904037 * l_ + 0.78277177 * m_ - 0.80867577 * s_;
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// Oklab → Oklch
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let c = (a * a + b * b).sqrt();
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let h = b.atan2(a); // radians
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Oklch { l, c, h, a: alpha }
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}
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// https://en.wikipedia.org/wiki/HSL_and_HSV#HSL_to_RGB
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fn from_hsl(hsl: Hsl) -> Color {
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let c = (1.0 - (2.0 * hsl.l - 1.0).abs()) * hsl.s;
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let h = hsl.h / 60.0;
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let x = c * (1.0 - (h.rem_euclid(2.0) - 1.0).abs());
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// https://en.wikipedia.org/wiki/Oklab_color_space#Conversions_between_color_spaces
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fn from_oklch(oklch: Oklch) -> Color {
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let Oklch { l, c, h, a: alpha } = oklch;
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let (r1, g1, b1) = if h < 1.0 {
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(c, x, 0.0)
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} else if h < 2.0 {
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(x, c, 0.0)
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} else if h < 3.0 {
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(0.0, c, x)
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} else if h < 4.0 {
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(0.0, x, c)
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} else if h < 5.0 {
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(x, 0.0, c)
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} else {
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// h < 6.0
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(c, 0.0, x)
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};
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let a = c * h.cos();
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let b = c * h.sin();
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let m = hsl.l - (c / 2.0);
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// Oklab → LMS (nonlinear)
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let l_ = l + 0.39633778 * a + 0.21580376 * b;
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let m_ = l - 0.105561346 * a - 0.06385417 * b;
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let s_ = l - 0.08948418 * a - 1.2914855 * b;
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Color {
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r: r1 + m,
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g: g1 + m,
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b: b1 + m,
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a: hsl.a,
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}
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// Cubing back
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let l = l_ * l_ * l_;
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let m = m_ * m_ * m_;
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let s = s_ * s_ * s_;
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let r = 4.0767417 * l - 3.3077116 * m + 0.23096994 * s;
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let g = -1.268438 * l + 2.6097574 * m - 0.34131938 * s;
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let b = -0.0041960863 * l - 0.7034186 * m + 1.7076147 * s;
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Color::from_linear_rgba(
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r.clamp(0.0, 1.0),
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g.clamp(0.0, 1.0),
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b.clamp(0.0, 1.0),
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alpha,
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)
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}
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