Chore: Restructure Repository for SvelteKit

_old/core/cover/coverHash.ts

@@ -0,0 +1,54 @@
+const THUMB_SIZE  = 16;
+const DUPE_THRESH = 0.12;
+
+const hashCache = new Map<string, Uint8ClampedArray>();
+
+function toGray(data: Uint8ClampedArray, pixels: number): Uint8ClampedArray {
+  const gray = new Uint8ClampedArray(pixels);
+  for (let i = 0; i < pixels; i++) {
+    const o = i * 4;
+    gray[i] = (data[o] * 299 + data[o + 1] * 587 + data[o + 2] * 114) / 1000;
+  }
+  return gray;
+}
+
+function loadThumb(url: string): Promise<Uint8ClampedArray> {
+  return new Promise((resolve, reject) => {
+    const img = new Image();
+    img.crossOrigin = "anonymous";
+    img.onload = () => {
+      const canvas = document.createElement("canvas");
+      canvas.width = canvas.height = THUMB_SIZE;
+      const ctx = canvas.getContext("2d")!;
+      ctx.drawImage(img, 0, 0, THUMB_SIZE, THUMB_SIZE);
+      resolve(toGray(ctx.getImageData(0, 0, THUMB_SIZE, THUMB_SIZE).data, THUMB_SIZE * THUMB_SIZE));
+    };
+    img.onerror = reject;
+    img.src = url;
+  });
+}
+
+function similarity(a: Uint8ClampedArray, b: Uint8ClampedArray): number {
+  let diff = 0;
+  for (let i = 0; i < a.length; i++) diff += Math.abs(a[i] - b[i]);
+  return diff / (a.length * 255);
+}
+
+export async function getHash(url: string): Promise<Uint8ClampedArray | null> {
+  if (hashCache.has(url)) return hashCache.get(url)!;
+  try {
+    const thumb = await loadThumb(url);
+    hashCache.set(url, thumb);
+    return thumb;
+  } catch {
+    return null;
+  }
+}
+
+export function areDuplicates(a: Uint8ClampedArray, b: Uint8ClampedArray): boolean {
+  return similarity(a, b) <= DUPE_THRESH;
+}
+
+export function clearHashCache(): void {
+  hashCache.clear();
+}