58 lines
1.4 KiB
TypeScript
58 lines
1.4 KiB
TypeScript
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/**
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* Calculate relative luminance of a color
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* Based on WCAG 2.1 specification
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*/
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export function getRelativeLuminance(r: number, g: number, b: number): number {
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const [rs, gs, bs] = [r, g, b].map((c) => {
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const sRGB = c / 255;
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return sRGB <= 0.03928 ? sRGB / 12.92 : Math.pow((sRGB + 0.055) / 1.055, 2.4);
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});
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return 0.2126 * rs + 0.7152 * gs + 0.0722 * bs;
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}
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/**
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* Calculate contrast ratio between two colors
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* Returns ratio from 1 to 21
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*/
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export function getContrastRatio(
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fg: { r: number; g: number; b: number },
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bg: { r: number; g: number; b: number }
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): number {
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const l1 = getRelativeLuminance(fg.r, fg.g, fg.b);
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const l2 = getRelativeLuminance(bg.r, bg.g, bg.b);
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const lighter = Math.max(l1, l2);
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const darker = Math.min(l1, l2);
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return (lighter + 0.05) / (darker + 0.05);
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}
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/**
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* Parse hex color to RGB
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*/
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export function hexToRgb(hex: string): { r: number; g: number; b: number } | null {
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const result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
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return result
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? {
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r: parseInt(result[1], 16),
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g: parseInt(result[2], 16),
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b: parseInt(result[3], 16),
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}
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: null;
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}
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/**
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* Check if a contrast ratio meets WCAG standards
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*/
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export function checkWCAGCompliance(ratio: number) {
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return {
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aa: {
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normalText: ratio >= 4.5,
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largeText: ratio >= 3,
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ui: ratio >= 3,
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},
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aaa: {
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normalText: ratio >= 7,
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largeText: ratio >= 4.5,
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},
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};
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}
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