Photos framework image from video at a certain frame - ios

Question

I have made a library collectionview filled with videos i fetch from the Photos framework, i use thumbnails to display all the different videos using the following method
func requestImageForAsset(_ asset: PHAsset!, targetSize targetSize: CGSize, contentMode contentMode: PHImageContentMode, options options: PHImageRequestOptions!, resultHandler resultHandler: ((UIImage!, [NSObject : AnyObject]!) -> Void)!) -> PHImageRequestID
which works fine.
But my videos always start with a black frame, so all the thumbnails are black. can I offset the frame from which it takes a snapshot image?

Answer 1

This is code i have used in my project which works like a charm for me
func generateThumnail(url: URL) -> UIImage? {
let asset = AVAsset(url: url)
let assetImgGenerate = AVAssetImageGenerator(asset: asset)
assetImgGenerate.appliesPreferredTrackTransform = true
assetImgGenerate.maximumSize = CGSize(width: 100, height: 100)
let time = CMTimeMake(1, 30)
if let img = try? assetImgGenerate.copyCGImage(at: time, actualTime: nil) {
return UIImage(cgImage: img)
}
return nil
}
The above function will return the image at 1 sec of the video
This is the way of passing the assetUrl of your video to get the thumbnail
func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [NSObject : AnyObject]) {
let mediaType = info[UIImagePickerControllerMediaType] as! String
if (mediaType == kUTTypeMovie as! String){
let tempVideo = info[UIImagePickerControllerMediaURL] as! URL
if let thumbnail = self.generateThumbnail(url: tempVideo) {
// Use your thumbnail
}

Answer 2

You can fetch the associated AVAsset object with
func requestAVAssetForVideo(_ asset: PHAsset,
options options: PHVideoRequestOptions?,
resultHandler resultHandler: (AVAsset?,
AVAudioMix?,
[NSObject : AnyObject]?) -> Void) -> PHImageRequestID
then load that asset into an AVAssetImageGenerator which is capable of fetching time-specific thumbnails via
func copyCGImageAtTime(_ requestedTime: CMTime,
actualTime actualTime: UnsafeMutablePointer<CMTime>,
error outError: NSErrorPointer) -> CGImage!

Answer 3

I think you need to be looking at the AVFoundation libraries to decode the video and grab the frame you want yourself.
To update the placeholders in the library looking at the docs it seems that you need to create a PHAssetChangeRequest and set the placeholderForCreatedAsset property on it. Then you need to request that the change be performed by the library within a changeblock.
Note: If this is only for your use you can set the placeholder frame within Photos and that should be reflected in your app.