AVAssetImageGenerator provides images rotated

When obtaining a UIImage of a video via AVAssetImageGenerator, I'm getting back images rotated (well, technically they're not) when the video is shot in portrait orientation. How can I tell what orientation the video was shot and then rotate the image properly?

AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:url options:nil];
AVAssetImageGenerator *generate = [[AVAssetImageGenerator alloc] initWithAsset:asset];
NSError *err = NULL;
CMTime time = CMTimeMake(0, 60);
CGImageRef imgRef = [generate copyCGImageAtTime:time actualTime:NULL error:&err];
[generate release];
UIImage *currentImg = [[UIImage alloc] initWithCGImage:imgRef];

The easiest way is to just set the appliesPreferredTrackTransform property on the image generator to YES, then it should automatically do the transformation for you.

The copy and paste solution to create image with the recording orientation using the previous answer.

AVURLAsset* asset = [AVURLAsset URLAssetWithURL:url options:nil];
AVAssetImageGenerator* imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:asset];
imageGenerator.appliesPreferredTrackTransform = YES;
CGImageRef cgImage = [imageGenerator copyCGImageAtTime:CMTimeMake(0, 1) actualTime:nil error:nil];
UIImage* image = [UIImage imageWithCGImage:cgImage];

CGImageRelease(cgImage);

Here is the solution in swift version 4:

func thumbnailImageForFileUrl(_ fileUrl: URL) -> UIImage? {
    let asset = AVAsset(url: fileUrl)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    
    do {
        
        let thumbnailCGImage = try imageGenerator.copyCGImage(at: CMTimeMake(1, 60), actualTime: nil)
        return UIImage(cgImage: thumbnailCGImage)
        
    } catch let err {
        print(err)
    }
    
    return nil
}

the easiest way is

imageGenerator.appliesPreferredTrackTransform = true

the hardest way is to change image orientation by this code:

let orient: UIImage.Orientation = isVertical ? .left: .up
imageView.image = UIImage(cgImage: image.cgImage!, scale: image.scale, orientation: orient)