Swift版本： 3.0

代码

1. 首先在info.plist内添加两个参数如下,给足权限，否则无法打开图库

   Key : Privacy - Media Library Usage Description
   Value : YES  [ It is not boolean,it is String ]
   
   Key : Privacy - Photo Library Usage Description
   Value : YES [ It is not boolean,it is String ]

2. 在ViewController中改为如下代码

   import UIKit
   // 首先在头部加入当前Controller需要遵从的代理
   class ViewController: UIViewController,UIImagePickerControllerDelegate,UINavigationControllerDelegate{
   
   override func viewDidLoad() {
       super.viewDidLoad()
       // Do any additional setup after loading the view,typically from a nib.
   }
   
   override func didReceiveMemoryWarning() {
       super.didReceiveMemoryWarning()
       // Dispose of any resources that can be recreated.
   }
   
   // 创建一个对象
   // 这个对象是用来在屏幕上显示
   @IBOutlet weak var imagePicked: UIImageView!
   // 这个Action方法对应着屏幕上的按钮，该按钮点击后会调用图库
   @IBAction func add(_ sender: UIBarButtonItem) {
   // 判断数据源是否合法，这里的.photoLibrary省略了其类名，Swift会自动推导
       if UIImagePickerController.isSourceTypeAvailable(.photoLibrary){
           let imagePicker = UIImagePickerController()
           imagePicker.delegate = self
           imagePicker.sourceType = .photoLibrary
           imagePicker.allowsEditing = true
           // 这一句，开始调用图库
           self.present(imagePicker,animated: true)
       }
   }
   // 实现代理的方法
   // 注意，这里和swift3.0之前的版本实现方法都不太一样，这是唯一的写法，网上流传的其他方法都是过时的
   
   func imagePickerController(_ picker: UIImagePickerController,didFinishPickingMediaWithInfo info: [String : Any]) {
       if let image = info[UIImagePickerControllerOriginalImage] as? UIImage{
       // 将图片显示给UIImageView
           imagePicked.image = image
       }else{
           print("pick image wrong")
       }
       // 收回图库选择界面
       self.dismiss(animated: true,completion: nil)
   }
   }

实际效果

打开图库

显示到界面

参考：
http://stackoverflow.com/questions/37925583/uiimagepickercontroller-crashes-app-swift3-xcode8

http://stackoverflow.com/questions/39009889/xcode-8-creating-an-image-format-with-an-unknown-type-is-an-error

完整demo百度云下载链接