truncate at 300 width

src/main.ts

@@ -134,7 +134,8 @@ function imageFromCanvas(img: HTMLImageElement, bg: HTMLImageElement, off: numbe
   const scale = th / h;
 
   const canvas = document.createElement('canvas');
-  canvas.width = w * scale + pw * 2;
+  const cw = w * scale + pw * 2;
+  canvas.width = cw >= 300 ? 300 : cw;
   canvas.height = th;
 
   const ctx = canvas.getContext('2d', { willReadFrequently: true })!;