128 lines
3.1 KiB
JavaScript
128 lines
3.1 KiB
JavaScript
const Mode = {
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Light: 1,
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Dark: 2,
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};
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/**
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* Convert to grayscale
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* @param {{r: number, g: number, b: number}} color
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* @returns Number between 0 and 255
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*/
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const colorToGrayscale = (color) => {
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return 0.3 * color.r + 0.59 * color.g + 0.11 * color.b;
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};
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/**
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* Extract color using canvas2d
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* @param {HTMLImageElement} image Image source
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* @returns Colors represeting the image
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*/
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const extractColors = (image) => {
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const canvas = document.createElement("canvas");
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canvas.width = image.naturalWidth || image.width;
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canvas.height = image.naturalHeight || image.height;
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const ctx = canvas.getContext("2d");
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ctx.drawImage(image, 0, 0);
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const imageData = ctx.getImageData(
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0,
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0,
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Math.max(1, canvas.width),
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Math.max(1, canvas.height)
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);
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const pixelData = imageData.data;
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const colors = [];
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for (let i = 0; i < pixelData.length; i += 4) {
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if (pixelData[i + 3] > 0) {
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colors.push({
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r: pixelData[i],
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g: pixelData[i + 1],
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b: pixelData[i + 2],
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});
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}
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}
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return colors;
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};
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/**
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* Change the color theme based on the mode
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* @param {Mode} mode
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*/
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const changeTheme = (mode) => {
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for (const item of document.getElementsByTagName("svg")) {
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const image = document.createElement("img");
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image.src = `data:image/svg+xml;base64,${btoa(
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new XMLSerializer().serializeToString(item)
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)}`;
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image.width = item.viewBox.baseVal.width;
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image.height = item.viewBox.baseVal.height;
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image.onload = () => {
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applyFilter(mode, item, extractColors(image));
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};
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}
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// SVG embedded in images as base64
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for (const item of document.getElementsByTagName("img")) {
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if (!item.src.startsWith("data:image/svg+xml;base64,")) {
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// Exclude image who aren't SVG and base64 encoded
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continue;
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}
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applyFilter(mode, item, extractColors(item));
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}
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};
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/**
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* Apply the filter based on the selected mode
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* @param {Mode} mode Current theme
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* @param {HTMLImageElement | SVGSVGElement} item Element
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* @param {{r: number, g: number, b: number}} colors Array of the colors of the element
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* @returns
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*/
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const applyFilter = (mode, item, colors) => {
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// Calculate the average grayscale value
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const grayscaleValues = colors.map(colorToGrayscale);
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const totalGrayscale = grayscaleValues.reduce((acc, val) => acc + val, 0);
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const averageGrayscale = totalGrayscale / grayscaleValues.length;
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const treshold = 128;
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const style = "filter: ";
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const dim = "brightness(0.8) contrast(1.2)";
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if (averageGrayscale < treshold && mode === Mode.Dark) {
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item.style = style + dim + " invert(1);";
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return;
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}
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if (averageGrayscale > treshold && mode === Mode.Light) {
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item.style = style + "invert(1);";
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return;
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}
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if (mode === Mode.Dark) {
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item.style = style + `${dim};`;
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return;
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}
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item.style = "";
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};
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window.addEventListener("load", () => {
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// Fix SVG images
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changeTheme(
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window.matchMedia("(prefers-color-scheme: dark)").matches
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? Mode.Dark
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: Mode.Light
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);
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});
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window
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.matchMedia("(prefers-color-scheme: dark)")
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.addEventListener("change", (event) =>
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changeTheme(event.matches ? Mode.Dark : Mode.Light)
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);
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