491f0cd08a
* Copyright headers 1 * Licence headers 2 * Copyright Headers 3 * Copyright Headers 4 * Copyright Headers 5 * Copyright Headers 6 * Copyright headers 7 * Add copyright headers for html and config file * Replace license files and update package.json * Update with CLA * lint
82 lines
2.4 KiB
TypeScript
82 lines
2.4 KiB
TypeScript
/*
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Copyright 2024 New Vector Ltd.
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Copyright 2019 Michael Telatynski <7t3chguy@gmail.com>
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SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
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Please see LICENSE files in the repository root for full details.
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*/
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import { split } from "lodash";
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export function textToHtmlRainbow(str: string): string {
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const frequency = (2 * Math.PI) / str.length;
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return split(str, "")
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.map((c, i) => {
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if (c === " ") {
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return c;
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}
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const [a, b] = generateAB(i * frequency, 1);
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const [red, green, blue] = labToRGB(75, a, b);
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return (
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'<span data-mx-color="#' +
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red.toString(16).padStart(2, "0") +
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green.toString(16).padStart(2, "0") +
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blue.toString(16).padStart(2, "0") +
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'">' +
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c +
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"</span>"
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);
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})
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.join("");
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}
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function generateAB(hue: number, chroma: number): [number, number] {
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const a = chroma * 127 * Math.cos(hue);
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const b = chroma * 127 * Math.sin(hue);
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return [a, b];
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}
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function labToRGB(l: number, a: number, b: number): [number, number, number] {
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// https://en.wikipedia.org/wiki/CIELAB_color_space#Reverse_transformation
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// https://en.wikipedia.org/wiki/SRGB#The_forward_transformation_(CIE_XYZ_to_sRGB)
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// Convert CIELAB to CIEXYZ (D65)
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let y = (l + 16) / 116;
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const x = adjustXYZ(y + a / 500) * 0.9505;
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const z = adjustXYZ(y - b / 200) * 1.089;
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y = adjustXYZ(y);
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// Linear transformation from CIEXYZ to RGB
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const red = 3.24096994 * x - 1.53738318 * y - 0.49861076 * z;
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const green = -0.96924364 * x + 1.8759675 * y + 0.04155506 * z;
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const blue = 0.05563008 * x - 0.20397696 * y + 1.05697151 * z;
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return [adjustRGB(red), adjustRGB(green), adjustRGB(blue)];
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}
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function adjustXYZ(v: number): number {
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if (v > 0.2069) {
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return Math.pow(v, 3);
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}
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return 0.1284 * v - 0.01771;
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}
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function gammaCorrection(v: number): number {
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// Non-linear transformation to sRGB
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if (v <= 0.0031308) {
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return 12.92 * v;
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}
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return 1.055 * Math.pow(v, 1 / 2.4) - 0.055;
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}
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function adjustRGB(v: number): number {
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const corrected = gammaCorrection(v);
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// Limits number between 0 and 1
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const limited = Math.min(Math.max(corrected, 0), 1);
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return Math.round(limited * 255);
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}
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