如何在 iOS 中从 ALAsset 获取视频缩略图？

我想从视频中获取每一帧的缩略图，然后将该图像保存在可变图像数组中。

我想用这些图像作为动画来播放。

NSURL* assetURL = [self.asset valueForProperty:ALAssetPropertyAssetURL];
NSDictionary* assetOptions = nil;

AVAsset* myAsset = [[AVURLAsset alloc] initWithURL:assetURL options:assetOptions];

self.imageGenerator = [AVAssetImageGenerator assetImageGeneratorWithAsset:myAsset];


int duration = CMTimeGetSeconds([myAsset duration]);

for(int i = 0; i<duration; i++)
{
    CGImageRef imgRef = [self.imageGenerator copyCGImageAtTime:CMTimeMake(i, duration) actualTime:NULL error:nil];
    UIImage* thumbnail = [[UIImage alloc] initWithCGImage:imgRef scale:UIViewContentModeScaleAspectFit orientation:UIImageOrientationUp];
    [thumbnailImages addObject:thumbnail];
}

我正在使用上面的代码来获取缩略图，但问题是如果有一个 2 秒的视频，我只能获取 2 个缩略图，但我想要 20 个缩略图（每秒 10 个缩略图）。

那么，如何使用CMTimeMake获取每0.1秒的缩略图

代码形式参考网址：视频中的缩略图 https://iosdevcenters.blogspot.com/2016/05/thumbnail-image-of-video-from.html

目标-C

-(UIImage *)generateThumbImage : (NSString *)filepath
{
    NSURL *url = [NSURL fileURLWithPath:filepath];

    AVAsset *asset = [AVAsset assetWithURL:url];
    AVAssetImageGenerator *imageGenerator = [[AVAssetImageGenerator alloc]initWithAsset:asset];
self.imageGenerator.appliesPreferredTrackTransform = YES; 
        CMTime time = [asset duration];
        time.value = 0;
        Float duration = CMTimeGetSeconds([myAsset duration]);
   for(Float i = 0.0; i<duration; i=i+0.1)
    {
     CGImageRef imgRef = [self.imageGenerator copyCGImageAtTime:CMTimeMake(i, duration) actualTime:NULL error:nil];
     UIImage* thumbnail = [[UIImage alloc] initWithCGImage:imgRef scale:UIViewContentModeScaleAspectFit orientation:UIImageOrientationUp];
    [thumbnailImages addObject:thumbnail];
    }
}

Swift

func generateThumbImage(url : NSURL) -> UIImage{
        var asset : AVAsset = AVAsset.assetWithURL(url) as! AVAsset
        var assetImgGenerate : AVAssetImageGenerator = AVAssetImageGenerator(asset: asset)
        assetImgGenerate.appliesPreferredTrackTransform = true
        var error       : NSError? = nil
        var time        : CMTime = CMTimeMake(1, 30)
        var img         : CGImageRef = assetImgGenerate.copyCGImageAtTime(time, actualTime: nil, error: &error)
        var frameImg    : UIImage = UIImage(CGImage: img)!

        return frameImg
    }