A film producer, an actor, a screenwriter and a director are same things in many ways. You can say that they are branches of same tree with different figures.
Producer: A producer is a film person and has money to spend but he or she has no guts to utilize and manage it. Producer knows that where to put its money. A producer needs a director to help with spending the money at right place at right time.
Director: A director is film person and he hasn’t money to utilize his management skills so this is why he needs an investor who would be a producer.
Screenwriter: A screenwriter is a film person and this person has thoughts and ideas but has no capability and courage to use them. A screenwriter has powerful imagination power but really sensitive and shy to express its feelings and emotions.
Actor: An actor is a film person and who is braver, more courageous, less shy, has high imagination power and sensitivity like a screenwriter.
Producer and director are more similar than screenwriters and actors.