i am a genius :D.
solution for non mac user:
1. press f12 and html source code window pops up
2.
click on this arrow and scan the oversized image
(i am using firefox. google chrome maybe a little different. but you need to scan or search for it)
3.
<canvas id="myCanvas" style="width: 1180px; height: 820px;" width="3000" height="3000"> </canvas>
change width and height to something like 3000
4. finished