如何将纯色应用于UISearchBar

let redColor = UIColor.red
let image = UIImage.imageWithColor(color: redColor)
searchBar.backgroundImage = image

searchBar.searchBarStyle = .default

let attributes: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.white]
searchBar.searchTextAttributes = attributes

searchBar.tintColor = UIColor.white

let placeholderAttributes: [NSAttributedString.Key: Any] = [.foregroundColor: UIColor.gray]
let attributedPlaceholder = NSAttributedString(string: "Search", attributes: placeholderAttributes)
searchBar.attributedPlaceholder = attributedPlaceholder