IOS 相册读取GIF数据

本文讨论的只只针对于UIImagePickerControllerDelegate,本文是用swift写的，oc相同。
由于iphone相册在ios11之前并不支持gif播放，但是其存储的是gif数据，但是如果选中的是gif数据，imagePicer方法返回的image只是gif的第一帧，那么如何获取到gif的真实数据呢？

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
}

官方描述：
Tells the delegate that the user picked a still image or movie.
告诉代理方用户选择了图片或者视频。

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看下参数：info
官方描述：
A dictionary containing the original image and the edited image, if an image was picked; or a filesystem URL for the movie, if a movie was picked. The dictionary also contains any relevant editing information. The keys for this dictionary are listed in Editing Information Keys.
如果选择了图像，则返回一个包含原始图像和已编辑图像的字典，如果选择了一个视频，则提供一个该视频的系统URL。

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由于ios11，对于info的内容作了一些修改，所以要根据系统区分对待。
ios11:

["UIImagePickerControllerImageURL": [file:///Users/xingfan/Library/Developer/CoreSimulator/Devices/5ECD6F60-71F4-4172-ACC8-9EBE83C923B2/data/Containers/Data/Application/2D69E94A-6D1A-44DA-82BF-FA5271DB5190/tmp/1FCBE42D-E6B8-4844-9F19-24E062CB9CBB.gif](file:///Users/xingfan/Library/Developer/CoreSimulator/Devices/5ECD6F60-71F4-4172-ACC8-9EBE83C923B2/data/Containers/Data/Application/2D69E94A-6D1A-44DA-82BF-FA5271DB5190/tmp/1FCBE42D-E6B8-4844-9F19-24E062CB9CBB.gif),
 "UIImagePickerControllerMediaType": public.image, 
 "UIImagePickerControllerPHAsset": <PHAsset: 0x7fdd71f4bb90> 11E12104-2923-4F9E-B70E-3AAEF98C40B6/L0/001 mediaType=1/32, sourceType=1, (700x690), creationDate=2018-08-17 09:01:54 +0000, location=0, hidden=0, favorite=0 , 
 "UIImagePickerControllerReferenceURL": assets-[library://asset/asset.GIF?id=11E12104-2923-4F9E-B70E-3AAEF98C40B6&ext=GIF](library://asset/asset.GIF?id=11E12104-2923-4F9E-B70E-3AAEF98C40B6&ext=GIF),
 "UIImagePickerControllerOriginalImage": <UIImage: 0x6040002a8400> size {700, 690} orientation 0 scale 1.000000]

ios8-10：

["UIImagePickerControllerMediaType": public.image,
 "UIImagePickerControllerReferenceURL": assets-[library://asset/asset.GIF?id=FDE27A54-A1C7-4C58-BA05-A75C27781D09&ext=GIF](library://asset/asset.GIF?id=FDE27A54-A1C7-4C58-BA05-A75C27781D09&ext=GIF), 
 "UIImagePickerControllerOriginalImage": <UIImage: 0x1740962b0> size {480, 800} orientation 0 scale 1.000000]

这里的思路是可以用photos框架获取gif的PHAsset（可以理解为系统数据的描述，并不是实际数据），PHImageManager获取data数据，这里可以控制同步或者异步。而这个data就是gif数据。

        let options = PHImageRequestOptions()
        options.version = .current
        //异步
        options.isSynchronous = true
        PHImageManager.default().requestImageData(for: imageAsset, options: options) { (data, str, origin, info) in
            DispatchQueue.main.async(execute: {
                self.myImage.gifImages = GifHelper.gifWithImages(gifData: data!)
                self.backGroundImageView.animationImages = self.myImage.gifImages
                self.backGroundImageView.animationDuration = 1
                self.backGroundImageView.startAnimating()
            })
        }

那么现在的问题就在如何获取到PHAsset实体，这里可以看到ios 11 中info直接返回了PHAsset实体，ios11之下的

let imgUrl = info[UIImagePickerControllerReferenceURL] as? URL
let imageAsset = PHAsset.fetchAssets(withALAssetURLs: [imgUrl!], options: nil).firstObject

这里fetchAssetsWithALAssetURLs在ios11中被废弃了，完整代码如下

//MARK:UIImagePickerControllerDelegate
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        let type:String = (info[UIImagePickerControllerMediaType]as!String)
        //当选择的类型是图片
        print("\(info)")
        if type=="public.image"{
            let imgUrl:URL?
            let imageAsset:PHAsset?
            if #available(iOS 11.0, *) {
                imgUrl = info[UIImagePickerControllerReferenceURL] as? URL
                imageAsset = info[UIImagePickerControllerPHAsset] as? PHAsset
            } else {
                imgUrl = info[UIImagePickerControllerReferenceURL] as? URL
                imageAsset = PHAsset.fetchAssets(withALAssetURLs: [imgUrl!], options: nil).firstObject
            }
            let img = info[UIImagePickerControllerOriginalImage] as? UIImage
            if imgUrl!.absoluteString.lowercased().contains("gif"){
                let options = PHImageRequestOptions()
                options.version = .current
                //异步
                options.isSynchronous = true
                PHImageManager.default().requestImageData(for: imageAsset, options: options) { (data, str, origin, info) in
                DispatchQueue.main.async(execute: {
                })
              }
            }
        }
    }