88 lines
2.5 KiB
TypeScript
88 lines
2.5 KiB
TypeScript
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/*
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Copyright 2019 Michael Telatynski <7t3chguy@gmail.com>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import { number } from "prop-types";
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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 Array.from(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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'<font 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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"</font>"
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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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// Convert CIELAB to CIEXYZ (D65)
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var 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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