You just can't tell 100% from an angled picture - I hate to do this as I've had a similar conversation in the VAR thread on offsides.
But to give an idea of why this isn't clear - have a look at the posts - they don't line up with the goal line because the photo is taken from slightly further up the pitch. This shows that anything above the goal line will appear further to the left the higher it is. That means the ball is going to appear further left in comparison to the goal line than it really is. Given that the whole of the ball has to be over the line, and it's pretty much just there, even in this picture, it looks like it's fine to me.