It works in Chrome or Firefox in both Windows or Android, but results in a flat plane in Safari in iOS. I have no idea why.
Original example in document:
I know that how f***ing can it be when debugging iOS Safari. It’s alright if no one can help me with this. Mutual encouragement.
Could it be the file format not accepted? I actually doubt iOS doesn’t support PNG, but - have you tried converting it to something else? a jpg? just to test if it is the file itself?
Maybe its a timing thing?
Ill look one second.
update
Dang I cant find my iPhone… sorry I wont be able to help on this one.
I can not repro 
is the original version working for you ?
It does work with another image:
So it seems there’s something with your .png file… As @RaananW suggested, try to use with another format than .png.
