add png compression to save space

compressImage.js

@@ -0,0 +1,27 @@
+import fs from 'fs/promises';
+import UPNG from 'upng-js';
+
+const countUniqueColors = (data) => {
+  const uniqueColors = new Set();
+  for (let i = 0; i < data.length; i += 4) {
+    uniqueColors.add(`${data[i]},${data[i + 1]},${data[i + 2]},${data[i + 3]}`);
+    if (uniqueColors.size > 256) {
+      return uniqueColors.size;
+    }
+  }
+  return uniqueColors.size;
+};
+
+export async function compressPng (filePath) {
+  const buffer = await fs.readFile(filePath);
+  const arrayBuffer = buffer.buffer.slice(buffer.byteOffset, buffer.byteOffset + buffer.byteLength);
+  const img = UPNG.decode(arrayBuffer);
+  const rgba = new Uint8Array(img.data);
+  const frameData = new Uint8Array(img.width * img.height * 4);
+  frameData.set(rgba.subarray(0, frameData.length));
+  const cnum = countUniqueColors(rgba) <= 256 ? 256 : 0;
+  const optimizedArrayBuffer = UPNG.encode([frameData.buffer], img.width, img.height, cnum, img.depth);
+  const optimizedBuffer = Buffer.from(optimizedArrayBuffer);
+  await fs.writeFile(filePath, optimizedBuffer);
+  return filePath;
+};