Are you on your largest chainring in this picture? (Chainrings being the large cogs by your pedals).
I see the chain deflecting slightly between the bottom of the lower jockey wheel (on the right in your picture), top of upper jockey, and bottom of the largest cassette cog:
This means the derailleur is taking slack out of the chain and could in theory stretch a little further (though you don't want it fully extended with that red line I drew becoming a straight line).
So if you're in your largest chainring I think you're OK. If you're not, your chain is probably slightly too short. It doesn't look to me like it can spool out enough remaining chain to go to a larger chainring.