How to make UINavigationBar Transparent in IOS 8?

I have tried a lot to make UINavigationBar transparent. But I failed making it so.The image which I set was transparent. Here is my code . Any help ? Thanks in advance.

 [rootNavC.navigationBar setBackgroundImage:[UIImage imageNamed:@"NAV_BG_iphone.png"] forBarMetrics:UIBarMetricsDefault];
rootNavC.navigationBar.translucent = YES;
rootNavC.navigationBar.backgroundColor = [UIColor clearColor];
[[UINavigationBar appearance] setTitleTextAttributes:@{
                           UITextAttributeTextColor : [UIColor whiteColor],
                     UITextAttributeTextShadowColor : [UIColor clearColor],
                    UITextAttributeTextShadowOffset : [NSValue valueWithUIOffset:UIOffsetMake(0, 0)],
                                UITextAttributeFont : [UIFont fontWithName:@"pastel" size:20]
 }];