swift4 透明背景VC

1. 新建一个demo，在StoryBoard上创建三个VC，如下图：

image.png

2. 新建两个VC，SecondViewController，和ThirdViewController，分别与StoryBoard的VC相关联。
   以SecondViewController举例：

image.png

3. 该拖线的拖线，添加点击事件。

4.代码部分：

ViewController

//
//  ViewController.swift
//  ClearBgVC
//
//  Created by iOS on 2018/10/16.
//  Copyright © 2018年 weiman. All rights reserved.
//

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
       
    }

     /// 弹出透明背景的VC，present进来的
    @IBAction func jumpToSecondVC(_ sender: Any) {
        let vc = SecondViewController.instance()
        vc.modalPresentationStyle = .custom
        vc.modalTransitionStyle = .crossDissolve
        present(vc, animated: true, completion: {})
    }
    
    @IBAction func jumpToThirdVC(_ sender: Any) {
        
        DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.5) { [weak self] in
            if let image = self?.normalSnapshotImage() {
                let vc = ThirdViewController.instance(image: image)
                self?.navigationController?.pushViewController(vc, animated: true)
            }
        }
    }
}

extension ViewController {
    
    /// 普通截图
    func normalSnapshotImage() -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(view.frame.size, false, UIScreen.main.scale)
        if let context = UIGraphicsGetCurrentContext() {
            view.layer.render(in: context)
            let image = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return image
        }
        return nil
    }
    
}

SecondViewController:

//
//  SecondViewController.swift
//  ClearBgVC
//
//  Created by iOS on 2018/10/16.
//  Copyright © 2018年 weiman. All rights reserved.
//

import UIKit

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        setup()
       
    }
    
    private func setup() {
        
    }
    
    class func instance() -> SecondViewController {
        let storyBoard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyBoard.instantiateViewController(withIdentifier: "SecondViewController") as! SecondViewController
        return vc
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        dismiss(animated: true)
    }

}

ThirdViewController:

//
//  ThirdViewController.swift
//  ClearBgVC
//
//  Created by iOS on 2018/10/16.
//  Copyright © 2018年 weiman. All rights reserved.
//

import UIKit

class ThirdViewController: UIViewController {
    
    @IBOutlet weak var bgImage: UIImageView!
    
    private var image: UIImage!
    
    override func viewDidLoad() {
        super.viewDidLoad()

        bgImage.image = image
    }
    
    class func instance(image: UIImage) -> ThirdViewController {
        let storyB = UIStoryboard.init(name: "Main", bundle: nil)
        let vc = storyB.instantiateViewController(withIdentifier: "ThirdViewController") as! ThirdViewController
        vc.image = image
        return vc
    }

}

效果：

QQ20181016-132820.gif