Petallica Paint's Output Picture Resolution is too Low with No Option to Configure it

I suggest a way for users to select their output resolution. The image resolution is a bit too small for my needs. 

**Like:**
**-50 DPI
-100 **DPI**
-300 DPI
-600 DPI**

_It is an amazing software and i would like to contribute codes to improve it in the near future_. 