第五十二篇、 OC获取视频的第一帧图片thumbnailImage

获取视频的第一帧图片 
有时候我们拍摄完视频后，希望获取一张图片当作这个视频的介绍，这个图片thumbnailImage可以从视频的第一帧获取到。

我们的思路是先获取视频的URL，然后初始化一个MPMoviePlayerController做工具，利用MPMoviePlayerController来拿图片，看具体代码如下：

- (void)imagePickerController:(UIImagePickerController *)picker   didFinishPickingMediaWithInfo:(NSDictionary *)info
{

NSString *mediaType = [info objectForKey: UIImagePickerControllerMediaType];

if (CFStringCompare ((__bridge CFStringRef) mediaType, kUTTypeMovie, ) == kCFCompareEqualTo) {
    NSURL *videoUrl=(NSURL*)[info objectForKey:UIImagePickerControllerMediaURL];
    NSString *moviePath = [videoUrl path];
    这里利用MPMoviePlayerController来获取
            MPMoviePlayerController *player = [[MPMoviePlayerController alloc]initWithContentURL:videoUrl] ;
            UIImage  *thumbnail = [player thumbnailImageAtTime:1.0 timeOption:MPMovieTimeOptionNearestKeyFrame];

            imageV.image = thumbnail;
            player = nil;//释放player

    NSString *videoCacheDir = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches/UploadPhoto/"];
    if (![[NSFileManager defaultManager] fileExistsAtPath:videoCacheDir]) {
        [[NSFileManager defaultManager] createDirectoryAtPath:videoCacheDir withIntermediateDirectories:YES attributes:nil error:nil];
    }
}
[self dismissViewControllerAnimated:YES completion:nil];

}