My dog barks and runs at people help!?

I have a Mini.Labradoodle who is two years old and has some behavior problems. For the past month I have been training him on lead to not bark at people as he growls and scares everyone normally! I have been distracting him with treats and praising him for being good or telling him off if he doesn't behave. He's good on lead (most of the time) but terrible off-lead and he loves to be off-lead - it keeps him in shape and he can run about with his friends.Today he ran up to a lady snarling and she was so scared! He does this to dogs he doesn't know as well. Its been suggested I put a muzzle on him but that doesn't sort the problem just masks it! Any suggestions?