regarding facebook post

Question

is there any way to send image on Facebook and twitter through xcode currently i am sending test through following code

NSMutableDictionary* params = [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                           @"", @"subject",msg, @"message", nil];

FBRequest *req = [FBRequest requestWithDelegate:self];
[req call:@"Stream.publish" params:params];

here msg is my text whatever i want to send i also need to send image on Facebook as well as twitter i have image name how can i do it

please help!!!!