Sketch app 3.3 exporting png with transparent background
I know this has been brought up before but it hasn't been resolved. I want to export a bunch of images which have a transparent background but maintain the dimensions of the transparent area. I've added a background and turned off the opacity but only the visible pixels are exportable.
Sketch has the most useless documentation about it http://bohemiancoding.com/sketch/support/documentation/11-exporting/2-slices.html
I've tried converting them to slices and symbols but that doesn't work either.
Here is the solution.