从UIImagePickerController抓取video的第一帧？
我试图从UIImagePickerController的选定的video中的第一帧显示在UIImageView ，但我不知道是否有可能。 如果是这样，我该怎么做？
您可以通过以下两种方法之一来完成此操作。 第一种方法是使用MPMoviePlayerController获取缩略图：
MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc] initWithContentURL:videoURL]; moviePlayer.shouldAutoplay = NO; UIImage *thumbnail = [moviePlayer thumbnailImageAtTime:time timeOption:MPMovieTimeOptionNearestKeyFrame];
这个工作，但MPMoviePlayerController不是一个特别轻量级的对象，不是特别快速抓取缩略图。
首选的方法是在AVFoundation中使用新的AVAssetImageGenerator。 这是比旧的方式快速，轻量级和更灵活。 这里有一个帮助器方法，它将从video中返回一个自动发布的图像。
+ (UIImage *)thumbnailImageForVideo:(NSURL *)videoURL atTime:(NSTimeInterval)time { 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 = time; 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; }
asynchronous使用
- (void)thumbnailImageForVideo:(NSURL *)videoURL atTime:(NSTimeInterval)time completion:(void (^)(UIImage *)) completion { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ 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 = time; 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; dispatch_async(dispatch_get_main_queue(), ^{ completion(thumbnailImage); }); }); }