164 lines
2.3 KiB
TypeScript
164 lines
2.3 KiB
TypeScript
/*
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Blurhash toolkit.
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base83 decoder/encoder is copied from
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https://github.com/woltapp/blurhash/blob/master/TypeScript/src/base83.ts,
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which is MIT Licensed: https://github.com/woltapp/blurhash?tab=MIT-1-ov-file#readme
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*/
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const digitCharacters = [
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"0",
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"1",
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"2",
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"3",
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"4",
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"5",
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"6",
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"7",
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"8",
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"9",
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"A",
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"B",
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"C",
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"D",
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"E",
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"F",
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"G",
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"H",
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"I",
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"J",
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"K",
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"L",
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"M",
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"N",
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"O",
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"P",
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"Q",
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"R",
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"S",
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"T",
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"U",
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"V",
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"W",
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"X",
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"Y",
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"Z",
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"a",
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"b",
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"c",
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"d",
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"e",
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"f",
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"g",
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"h",
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"i",
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"j",
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"k",
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"l",
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"m",
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"n",
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"o",
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"p",
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"q",
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"r",
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"s",
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"t",
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"u",
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"v",
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"w",
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"x",
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"y",
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"z",
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"#",
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"$",
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"%",
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"*",
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"+",
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",",
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"-",
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".",
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":",
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";",
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"=",
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"?",
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"@",
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"[",
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"]",
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"^",
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"_",
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"{",
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"|",
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"}",
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"~",
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];
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function decode83(str: string) {
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let value = 0;
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for (let i = 0; i < str.length; i++) {
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const c = str[i];
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const digit = digitCharacters.indexOf(c);
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value = value * 83 + digit;
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}
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return value;
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}
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function encode83(n: number, length: number): string {
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var result = "";
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for (let i = 1; i <= length; i++) {
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let digit = (Math.floor(n) / Math.pow(83, length - i)) % 83;
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result += digitCharacters[Math.floor(digit)];
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}
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return result;
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}
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/* toColorHex() is modified from
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https://www.xaymar.com/articles/2020/12/08/fastest-uint8array-to-hex-string-conversion-in-javascript/,
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licensed BSD-3. */
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// Pre-Init
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const LUT_HEX_4b = [
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"0",
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"1",
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"2",
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"3",
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"4",
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"5",
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"6",
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"7",
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"8",
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"9",
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"A",
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"B",
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"C",
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"D",
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"E",
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"F",
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];
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const LUT_HEX_8b = new Array(0x100);
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for (let n = 0; n < 0x100; n++) {
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LUT_HEX_8b[n] = `${LUT_HEX_4b[(n >>> 4) & 0xf]}${LUT_HEX_4b[n & 0xf]}`;
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}
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// End Pre-Init
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function toColorHex(buffer: Uint8ClampedArray): `#${string}` {
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let out = "#";
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for (let idx = 0, edx = buffer.length; idx < edx; idx++) {
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out += LUT_HEX_8b[buffer[idx]];
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}
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return out as `#${string}`;
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}
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export function averageColor(blurhash: string) {
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const v = decode83(blurhash.substring(2, 6)); // 24-bit RGB
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return [v >> 16, (v >> 8) & 255, v & 255] as const;
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}
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export function averageColorHex(blurhash: string) : `#${string}` {
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const [r, g, b] = averageColor(blurhash);
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const buf = new Uint8ClampedArray(3);
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buf[0] = r;
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buf[1] = g;
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buf[2] = b;
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return toColorHex(buf);
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}
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