Touch Issue in mobile version or in Responsive mode.

Hi @weihanchen 

This tool is very nice and very helpful for me, thank you so much for this buddy.

I don't have angular js knowledge, but i have completed my app 90%, remaining 10% is mobile responsive. 

Here, i getting problem in responsive mode, When i am trying to crop screen then its preventing to crop.

I hope you will help me, i am waiting for your response.

Thanks.