[FEAT] High resolution transparent images

[jmigual]

Is your feature request related to a problem? Please describe.
Generated PNGs do not have a transparent background and there is not option to enable it.

Describe the solution you'd like
I would like to be able to export my blueprint as a high resolution PNG with transparent background

Describe alternatives you've considered
Since I want a high resolution image without background I screenshot the screen and then edit the screenshot with GIMP to remove the background. It's quite tedious and it should be fairly easy to add an option for this.