1.install pod - pod "BSImagePicker", "~> 2.8"
- inside info plist add row  Privacy - Photo Library Usage Description
3.paste below code inside a .swift file- 
    import UIKit
    import BSImagePicker
    import Photos
    class MultipleImgViC: UIViewController {
        @IBOutlet weak var imageView: UIImageView!
        var SelectedAssets = [PHAsset]()
        var photoArray = [UIImage]()
        override func viewDidLoad() {
            super.viewDidLoad()
        }
        @IBAction func selectImages(_ sender: Any) {
            let vc = BSImagePickerViewController()
            self.bs_presentImagePickerController(vc, animated: true, select: { (assest: PHAsset) -> Void in
            },
                                                 deselect: { (assest: PHAsset) -> Void in
        }, cancel: { (assest: [PHAsset]) -> Void in
        }, finish: { (assest: [PHAsset]) -> Void in
            for i in 0..<assest.count
            {
                    self.SelectedAssets.append(assest[i])
            }
            self.convertAssetToImages()
        }, completion: nil)
    }
    @IBAction func dismissview(_ sender: Any) {
        dismiss(animated: true, completion: nil)
    }
}
extension MultipleImgViC{
    func convertAssetToImages() -> Void {
        if SelectedAssets.count != 0{
            for i in 0..<SelectedAssets.count{
                let manager = PHImageManager.default()
                let option = PHImageRequestOptions()
                var thumbnail = UIImage()
                option.isSynchronous = true
                manager.requestImage(for: SelectedAssets[i], targetSize: CGSize(width: 200, height: 200), contentMode: .aspectFill, options: option, resultHandler: {(result,info) -> Void in
                    thumbnail = result!
                })
                let data = thumbnail.jpegData(compressionQuality: 0.7)
                let newImage = UIImage(data: data!)
                self.photoArray.append(newImage! as UIImage)
            }
            self.imageView.animationImages = self.photoArray
            self.imageView.animationDuration = 3.0
            self.imageView.startAnimating()
        }
    }
}
Note :- if pod file give "How to fix “SWIFT_VERSION '3.0' is unsupported, supported versions are: 4.0, 4.2, 5.0” error in Xcode 10.2?
" this error then solve it from this link:- https://stackoverflow.com/a/55901964/8537648
video reference: - https://youtu.be/B1DelPi1L0U
sample image:-