I am sorry but you can not tell 100% by just a picture male or female sorry dont care who you are its not possible unless it is very distinct male with a huge kok on the head but by the looks of this picture it is anyone "guess" venting is the best way to get 100% accurate
it is true that u wont be 100% accurate without venting. But most of the time u can tell by the anal fin if the fish are mature enough. The males will have a clearly extended anal fin just like the one on the left. its a pretty good bet on it and its wayyyy less invasive than catching the fish and actually flipping it over but of course there are other factors u have to consider too not just the extended anal fin. OP if u really really need to know just vent them. just fyi joshs801 some people can actually tell male female very accurately
On numerous occasions i have asked a fellow member to sex a couple of pbass just by anal fins that i were interested in buying for my used to be breeding project before i even put time into meeting the seller. And i wen i actually vented the fishes that i purchased they turned out to be the sex he had said they wud most likely be. and this wasnt a one time thing either
....its all good though there should be no fight over something like tis lol