feat(browser): clamp screenshots under 5MB

src/browser/screenshot.ts

@@ -0,0 +1,69 @@
+import sharp from "sharp";
+
+export const DEFAULT_BROWSER_SCREENSHOT_MAX_SIDE = 2000;
+export const DEFAULT_BROWSER_SCREENSHOT_MAX_BYTES = 5 * 1024 * 1024;
+
+export async function normalizeBrowserScreenshot(
+  buffer: Buffer,
+  opts?: {
+    maxSide?: number;
+    maxBytes?: number;
+  },
+): Promise<{ buffer: Buffer; contentType?: "image/jpeg" }> {
+  const maxSide = Math.max(
+    1,
+    Math.round(opts?.maxSide ?? DEFAULT_BROWSER_SCREENSHOT_MAX_SIDE),
+  );
+  const maxBytes = Math.max(
+    1,
+    Math.round(opts?.maxBytes ?? DEFAULT_BROWSER_SCREENSHOT_MAX_BYTES),
+  );
+
+  const meta = await sharp(buffer, { failOnError: false }).metadata();
+  const width = Number(meta.width ?? 0);
+  const height = Number(meta.height ?? 0);
+  const maxDim = Math.max(width, height);
+
+  if (
+    buffer.byteLength <= maxBytes &&
+    (maxDim === 0 || (width <= maxSide && height <= maxSide))
+  ) {
+    return { buffer };
+  }
+
+  const qualities = [85, 75, 65, 55, 45, 35];
+  const sideStart = maxDim > 0 ? Math.min(maxSide, maxDim) : maxSide;
+  const sideGrid = [sideStart, 1800, 1600, 1400, 1200, 1000, 800]
+    .map((v) => Math.min(maxSide, v))
+    .filter((v, i, arr) => v > 0 && arr.indexOf(v) === i)
+    .sort((a, b) => b - a);
+
+  let smallest: { buffer: Buffer; size: number } | null = null;
+
+  for (const side of sideGrid) {
+    for (const quality of qualities) {
+      const out = await sharp(buffer, { failOnError: false })
+        .resize({
+          width: side,
+          height: side,
+          fit: "inside",
+          withoutEnlargement: true,
+        })
+        .jpeg({ quality, mozjpeg: true })
+        .toBuffer();
+
+      if (!smallest || out.byteLength < smallest.size) {
+        smallest = { buffer: out, size: out.byteLength };
+      }
+
+      if (out.byteLength <= maxBytes) {
+        return { buffer: out, contentType: "image/jpeg" };
+      }
+    }
+  }
+
+  const best = smallest?.buffer ?? buffer;
+  throw new Error(
+    `Browser screenshot could not be reduced below ${(maxBytes / (1024 * 1024)).toFixed(0)}MB (got ${(best.byteLength / (1024 * 1024)).toFixed(2)}MB)`,
+  );
+}