Edge encode fix (#211)

* No canvas.toBlob in Edge.

* pffft

src/lib/util.ts

@@ -30,7 +30,28 @@ export async function canvasEncode(data: ImageData, type: string, quality?: numb
   if (!ctx) throw Error('Canvas not initialized');
   ctx.putImageData(data, 0, 0);
 
-  const blob = await new Promise<Blob | null>(r => canvas.toBlob(r, type, quality));
+  let blob: Blob | null;
+
+  if ('toBlob' in canvas) {
+    blob = await new Promise<Blob | null>(r => canvas.toBlob(r, type, quality));
+  } else {
+    // Welcome to Edge.
+    // TypeScript thinks `canvas` is 'never', so it needs casting.
+    const dataUrl = (canvas as HTMLCanvasElement).toDataURL(type, quality);
+    const result = /data:([^;]+);base64,(.*)$/.exec(dataUrl);
+
+    if (!result) throw Error('Data URL reading failed');
+
+    const outputType = result[1];
+    const binaryStr = atob(result[2]);
+    const data = new Uint8Array(binaryStr.length);
+
+    for (let i = 0; i < data.length; i += 1) {
+      data[i] = binaryStr.charCodeAt(i);
+    }
+
+    blob = new Blob([data], { type: outputType });
+  }
 
   if (!blob) throw Error('Encoding failed');
   return blob;