Advanced Color Math

/advanced-color-math

When to Use

• Generating multi-stop palettes programmatically (brand → 10-step scale)
• Dark mode: finding perceptually equal light/dark pairs
• Enforcing WCAG AA/AAA contrast ratios automatically
• CSS color-mix() and oklch() in production
• Extracting dominant color from user-uploaded images

Do NOT use for

• Static palette picking (use a color tool instead)
• Consumer branding decisions (perceptual math ≠ brand taste)

Color Space Decision Tree

Need gradient?          → oklch() — uniform hue, no "muddy middle"
Need dark-mode pair?    → LCH lightness mirror (L=30↔L=70)
Need contrast check?    → WCAG relative luminance (sRGB → linear)
Need gamut mapping?     → CSS color-gamut: p3 + @supports
Need tint/shade scale?  → Ant Design algorithm (HSB rotation)

OKLAB/OKLCH Perceptual Gradient (culori + bottosson/oklab)

import { interpolate, formatHex } from 'culori'

// OKLCH gradient — hue stays vivid, no gray muddy middle
const gradient = interpolate(['#3b82f6', '#ec4899'], 'oklch')
const stops = Array.from({ length: 11 }, (_, i) => formatHex(gradient(i / 10)))
// → smooth blue-to-pink, no desaturated midpoint

// CSS native (Chrome 111+)
background: linear-gradient(to right,
  oklch(62% 0.2 264),
  oklch(64% 0.28 0)
);

Dark-Mode Pair Algorithm (Atlassian + Radix UI)

import { wcagContrast } from 'culori'

// Mirror at L=50 in OKLCH, then nudge for contrast
function darkPair(lightHex) {
  const c = oklch(lightHex)
  const darkL = c.l > 0.5 ? 1 - c.l + 0.05 : c.l
  const candidate = { mode: 'oklch', l: darkL, c: c.c, h: c.h }
  // Enforce 4.5:1 on dark bg (#1a1a1a = L≈0.12)
  return wcagContrast(candidate, '#1a1a1a') >= 4.5
    ? formatHex(candidate)
    : lighten(candidate, 0.1)  // nudge until passing
}

Ant Design 10-Step Palette Algorithm

// Hue rotation: darks shift -4°, lights shift +10°
// Saturation: darks -9%, lights pinned at input S
// Brightness: 10 steps from 95% (lightest) → input B (darkest)
function generatePalette(hex) {
  const [h, s, b] = toHSB(hex)
  return Array.from({ length: 10 }, (_, i) => {
    const t = i / 9
    const hShift = t < 0.5 ? h + 10 * (1 - t * 2) : h - 4 * (t - 0.5) * 2
    const sVal = t < 0.5 ? s * (t * 2) : s
    const bVal = 95 - (95 - b) * t
    return fromHSB(hShift, sVal, bVal)
  })
}

WCAG Contrast Enforcement (tinycolor2 / culori)

import { wcagContrast } from 'culori'

function enforceContrast(fg, bg, level = 'AA') {
  const min = level === 'AAA' ? 7 : 4.5
  let candidate = fg
  while (wcagContrast(candidate, bg) < min) {
    // Darken fg by 5% OKLCH lightness
    candidate = adjust(candidate, { l: -0.05 })
    if (oklch(candidate).l < 0.05) break  // give up at pure black
  }
  return formatHex(candidate)
}

// Radix UI approach: pre-compute all 12-step scales so any fg/bg combo passes

CSS color-mix() + Gamut Mapping

/* CSS native blend — no JS needed */
.badge-muted {
  background: color-mix(in oklch, var(--color-primary) 20%, transparent);
}

/* P3 wide gamut with sRGB fallback */
.vibrant {
  color: #ff6b6b;  /* sRGB fallback */
  color: color(display-p3 1 0.3 0.3);  /* wider gamut */
}

/* Gamut-safe oklch */
@supports (color: oklch(0 0 0)) {
  .vibrant { color: oklch(65% 0.28 27); }
}

Image Color Extraction (vibrant.js / color-thief pattern)

import Vibrant from 'node-vibrant'

const palette = await Vibrant.from(imageUrl).getPalette()
// Swatches: Vibrant, LightVibrant, DarkVibrant, Muted, LightMuted, DarkMuted
const primary = palette.Vibrant?.hex ?? '#3b82f6'
const '#fff') >= 4.5 ? '#fff' : '#000'

// nivo uses this pattern for chart auto-coloring from data

Anti-Fake-Pass Checklist

❌ Gradient interpolated in sRGB (desaturated gray midpoint)
❌ Dark-mode color picked visually without contrast check
❌ Palette steps with identical perceived lightness
❌ color-mix() used without sRGB fallback
❌ Image color extraction used without WCAG check on extracted color
❌ oklch() used in production without @supports guard