保存图片至相册

• 保存图片至相册功能需要注意，需要将 NSPhotoLibraryAddUsageDescription 授权请求添加到Info.plist文件中。不然在调用保存图片API时，app会闪退，并报错:
  This app has crashed because it attempted to access privacy-sensitive data without a usage description. The app's Info.plist must contain an NSPhotoLibraryAddUsageDescription key with a string value explaining to the user how the app uses this data.

Info.plist文件的配置

代码：

//保存图片至相册
UIImageWriteToSavedPhotosAlbum(finalImage, self, #selector(self.image(image:didFinishSavingWithError:contextInfo:)), nil)

/// 图片保存成功或失败的回调方法
@objc func image(image:UIImage,didFinishSavingWithError error:NSError?,contextInfo:AnyObject) {
    if error != nil {
        //...保存图片失败
    } else {
        //...保存图片成功
    }
}