通过 UIImagepickerController 快速获取元数据答案

【问题标题】：Getting metadata in swift by UIImagepickerController通过 UIImagepickerController 快速获取元数据
【发布时间】：2014-10-15 20:06:49
【问题描述】：

我正在尝试在 SWIFT 中为 Objective-C 实现iOS 8 UIImage Metadata 中的答案，如下所示

//source: http://stackanswers.com/questions/24227578/ios-8-uiimage-metadata
func metaDataFromAssetLibrary(info: NSDictionary) {

    var assetURL = info.objectForKey(UIImagePickerControllerReferenceURL) as NSURL
    var assetLibrary = ALAssetsLibrary()
    assetLibrary.assetForURL(assetURL as NSURL, resultBlock: {
        (asset: ALAsset!) in
            var metadata: NSDictionary = asset.defaultRepresentation().metadata() as NSDictionary
            NSLog ("imageMetaData from AssetLibrary %@",metadata);

        }, failureBlock: {
            (error: NSError!) in

            NSLog("Error!")
    })

}

我用

来称呼它

func imagePickerController(picker: UIImagePickerController!, didFinishPickingMediaWithInfo info: NSDictionary!){

    // https://stackoverflow.com/questions/3088874/didfinishpickingmediawithinfo-return-nil-photo
    picker.dismissViewControllerAnimated(true, completion: nil)

    let image = info.objectForKey("UIImagePickerControllerOriginalImage") as UIImage

    PHPhotoLibrary.sharedPhotoLibrary().performChanges({
        let createAssetRequest = PHAssetChangeRequest.creationRequestForAssetFromImage(image)
        let assetPlaceholder = createAssetRequest.placeholderForCreatedAsset
        let albumChangeRequest = PHAssetCollectionChangeRequest(forAssetCollection: self.assetCollection, assets: self.photosAsset)

        albumChangeRequest.addAssets([assetPlaceholder])
        }, completionHandler: {(success, error)in
            NSLog("Adding Image to Library -> %@", (success ? "Sucess":"Error!"))
            picker.dismissViewControllerAnimated(true, completion: nil)
    })
    metaDataFromAssetLibrary(info)

}

这会导致“致命错误：在展开可选值时意外发现 nil”

【问题讨论】：

标签： ios swift

【解决方案1】：

试试这个代码：

let metadata = info[UIImagePickerControllerMediaMetadata] as? NSDictionary    
let image = info[UIImagePickerControllerOriginalImage] as? UIImage

【讨论】：

UIImagePickerControllerMediaMetadata 仅在图像来自相机而非照片库时有效。

【解决方案2】：

如果你从相机获取图像，你可以从info[UIImagePickerControllerMediaMetadata]获取metadata。

但是，当您从相册中选择图片时，没有info[UIImagePickerControllerMediaMetadata]，而是info[UIImagePickerControllerReferenceURL]!

【讨论】：