如何在iPhone App中将第一帧视频显示为缩略图？

Question

我正在创建一个iPhone应用程序，用户可以在其中捕获视频，当他完成该操作时，该视频的第一帧应该显示为缩略图。 如何显示该图像，我的意思是如何提取第一帧视频？ 谢谢 -

Answer 1

有两种选择： -

1）使用MPMoviePlayerController。

MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc]
                                       initWithContentURL:videoURL];
moviePlayer.shouldAutoplay = NO;
UIImage *thumbnail = [moviePlayer thumbnailImageAtTime:time
                     timeOption:MPMovieTimeOptionNearestKeyFrame];

2）使用AVURLAsset

AVURLAsset *asset=[[AVURLAsset alloc] initWithURL:self.url options:nil];
AVAssetImageGenerator *generator = [[AVAssetImageGenerator alloc] initWithAsset:asset];
generator.appliesPreferredTrackTransform=TRUE;
[asset release];
CMTime thumbTime = CMTimeMakeWithSeconds(0,30);

AVAssetImageGeneratorCompletionHandler handler = ^(CMTime requestedTime, CGImageRef im, CMTime actualTime, AVAssetImageGeneratorResult result, NSError *error){
    if (result != AVAssetImageGeneratorSucceeded) {
        NSLog(@"couldn't generate thumbnail, error:%@", error);
    }
    [button setImage:[UIImage imageWithCGImage:im] forState:UIControlStateNormal];
    thumbImg=[[UIImage imageWithCGImage:im] retain];
    [generator release];
};

CGSize maxSize = CGSizeMake(320, 180);
generator.maximumSize = maxSize;
[generator generateCGImagesAsynchronouslyForTimes:[NSArray arrayWithObject:[NSValue valueWithCMTime:thumbTime]] completionHandler:handler];