获取视频的第一帧图片

+ (UIImage *)getFirstFrameOfVideoWithVideoURL:(NSURL *)videoURL
{
    AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
    NSParameterAssert(asset);
    AVAssetImageGenerator *assetIG = [[AVAssetImageGenerator alloc] initWithAsset:asset];

    assetIG.appliesPreferredTrackTransform = YES;
    assetIG.apertureMode = AVAssetImageGeneratorApertureModeEncodedPixels;

    CGImageRef thumbnailImageRef = NULL;
    CFTimeInterval thumbnailImageTime = 60;
    NSError *igError = nil;
    thumbnailImageRef = [assetIG copyCGImageAtTime:CMTimeMake(thumbnailImageTime, 60) actualTime:NULL error:&igError];

    if (!thumbnailImageRef)
        NSLog(@"thumbnailImageGenerationError %@", igError );

    UIImage *thumbnailImage = thumbnailImageRef ? [[UIImage alloc] initWithCGImage:thumbnailImageRef] : nil;

    return thumbnailImage;
}