把颜色转成图片

func imageFromColor(color: UIColor) -> UIImage {
        let rect: CGRect = CGRectMake(0, 0, view.frame.size.width, view.frame.size.height)
        UIGraphicsBeginImageContext(rect.size)
        let context: CGContextRef = UIGraphicsGetCurrentContext()!
        CGContextSetFillColorWithColor(context, color.CGColor)
        CGContextFillRect(context, rect)
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsGetCurrentContext()
        return image
    }

-------------------------可以用它把导航栏底下的黑线去掉-----------------------------------

 override func viewDidLoad() {
        super.viewDidLoad()

        navigationController?.navigationBar.setBackgroundImage(imageFromColor(mainColor), forBarPosition: UIBarPosition.Any, barMetrics: UIBarMetrics.Default)
        
        navigationController?.navigationBar.shadowImage = UIImage()

    }

  func imageFromColor(color: UIColor) -> UIImage {
        let rect: CGRect = CGRectMake(0, 0, view.frame.size.width, view.frame.size.height)
        UIGraphicsBeginImageContext(rect.size)
        let context: CGContextRef = UIGraphicsGetCurrentContext()!
        CGContextSetFillColorWithColor(context, color.CGColor)
        CGContextFillRect(context, rect)
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsGetCurrentContext()
        return image
    }