Fix SVG pictures in dark themes

static/js/cours.js

@@ -80,6 +80,61 @@ const deepestNodeOpened = (path, options) => {
   }
 };
 
+const svgDarkTheme = () => {
+  for (const item of document.getElementsByTagName("img")) {
+    if (!item.src.startsWith("data:image/svg+xml;base64,")) {
+      // Exclude image who aren't SVG and base64 encoded
+      break;
+    }
+
+    /** Convert to grayscale */
+    const colorToGrayscale = (color) => {
+      return 0.3 * color.r + 0.59 * color.g + 0.11 * color.b;
+    };
+
+    /** Extract color using canvas2d */
+    const extractColors = (image) => {
+      const canvas = document.createElement("canvas");
+      canvas.width = image.width;
+      canvas.height = image.height;
+      const ctx = canvas.getContext("2d");
+      ctx.drawImage(image, 0, 0);
+      const imageData = ctx.getImageData(
+        0,
+        0,
+        Math.max(1, canvas.width),
+        Math.max(1, canvas.height)
+      );
+      const pixelData = imageData.data;
+
+      const colors = [];
+      for (let i = 0; i < pixelData.length; i += 4) {
+        if (pixelData[i + 3] > 0) {
+          colors.push({
+            r: pixelData[i],
+            g: pixelData[i + 1],
+            b: pixelData[i + 2],
+          });
+        }
+      }
+
+      return colors;
+    };
+
+    // Extract colors
+    const colors = extractColors(item);
+
+    // Calculate the average grayscale value
+    const grayscaleValues = colors.map(colorToGrayscale);
+    const totalGrayscale = grayscaleValues.reduce((acc, val) => acc + val, 0);
+    const averageGrayscale = totalGrayscale / grayscaleValues.length;
+
+    if (averageGrayscale < 128) {
+      item.style = "filter: invert(1);";
+    }
+  }
+};
+
 window.addEventListener("load", () => {
   // Build the filetree
   const fileTreeElement = document.getElementsByTagName("aside")[0];
@@ -101,4 +156,7 @@ window.addEventListener("load", () => {
   );
 
   uncollapse(last_openeded);
+
+  // Fix SVG images
+  svgDarkTheme();
 });