TabBarItem的图片渲染模式

在ios7.0以后，UIImage有一个方法可以直接返回 以一种 渲染模式 渲染的UIImage

// Create a version of this image with the specified rendering mode. By default, images have a rendering mode of UIImageRenderingModeAutomatic.
    @available(iOS 7.0, *)
    public func imageWithRenderingMode(renderingMode: UIImageRenderingMode) -> UIImage

例子

child.tabBarItem.image = UIImage(named: imageName + "_normal")?.imageWithRenderingMode(.AlwaysOriginal)
child.tabBarItem.selectedImage = UIImage(named:imageName + "_selected")?.imageWithRenderingMode(.AlwaysOriginal)

这样，就可以将图片本来的样子展示在TabBar上面了