Builder ? :
yourButton.bounds = CGRectMake( 0, 0, yourImage.size.width, yourImage.size.height );
, , :
UIImage *image = [UIImage imageNamed:@"audio-off.png"];
UIButton *myMuteButton = [UIButton buttonWithType:UIButtonTypeCustom];
myMuteButton.bounds = CGRectMake( 0, 0, image.size.width, image.size.height );
[myMuteButton setImage:image forState:UIControlStateNormal];
[myMuteButton addTarget:self action:@selector(mute) forControlEvents:UIControlEventTouchUpInside];
UIBarButtonItem *myMuteBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:myMuteButton];
navBar.leftBarButtonItem = myMuteBarButtonItem;
[myMuteBarButtonItem release];