So far I have the effect working by using the gaussian blur shader, and just moving around masks through blueprint to have it only affect the parts of the screen I need. (See attached image) It works, but performance is not amazing…
I’m not sure I understand how you would achieve any blur through a custom image with transparency - could you elaborate?
I’ve searched around a lot, and as far as I can tell, there is in fact no way to mask or change the shape of the UMG background blur, so this is the only way right now I can think of.
This is certainly a tricky effect to achieve in UE4, it would seem 
