有了GPUImage，我们可以十分方便的给视频添加滤镜。例如，我们可以在播放时实时的给视频添加滤镜，以观察效果。代码如下：

  //播放视频
    AVPlayerItem *item =[[AVPlayerItem alloc]initWithURL:_videoURL];
    AVPlayer *player =[[AVPlayer alloc]initWithPlayerItem:item];
    AVPlayerLayer *playerLayer =[AVPlayerLayer playerLayerWithPlayer:player];
    playerLayer.frame =self.view.bounds;
    [self.view.layer addSublayer:playerLayer];
    
    movieFile =[[GPUImageMovie alloc]initWithPlayerItem:item];
    movieFile.runBenchmark =YES;
    movieFile.playAtActualSpeed =YES;
    
    filter =[[GPUImageSketchFilter alloc] init];
    [movieFile addTarget:filter];
    
    filterView =[[GPUImageView alloc]initWithFrame:self.view.bounds];
    [self.view addSubview:filterView];
    [filter addTarget:filterView];
    
    [player play];
    [movieFile startProcessing];

而把添加滤镜后的视频保存到本地的话 ，则需要GPUImage框架中的GPUImageMovieWriter这个类写到本地即可，还是贴代码：

 dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
        
        
//        [movieFile removeAllTargets];
//        //新的滤镜
//        filter =[[GPUImageSepiaFilter alloc]init];
//
//        [movieFile addTarget:filter];
//        [filter addTarget:filterView];
        
        //movieWriter 写到本地
        endMovieFile =[[GPUImageMovie alloc]initWithURL:_videoURL];
        endMovieFile.runBenchmark =YES;
        endMovieFile.playAtActualSpeed =YES;
        
        endFilter =[[GPUImageSepiaFilter alloc]init];
        [endMovieFile addTarget:endFilter];
        
        
        
        NSString *pathToMovie =[self getVideoSaveFilePathString:@".MOV" addPathArray:NO];
        unlink([pathToMovie UTF8String]);
        NSURL *movieURL = [NSURL fileURLWithPath:pathToMovie];
        
        movieWriter =[[GPUImageMovieWriter alloc]initWithMovieURL:movieURL size:CGSizeMake(720, 1280)];
        [endFilter addTarget:movieWriter];
        
        movieWriter.shouldPassthroughAudio =YES;
        endMovieFile.audioEncodingTarget =movieWriter;
        [endMovieFile enableSynchronizedEncodingUsingMovieWriter:movieWriter];
        [movieWriter startRecording];
        [endMovieFile startProcessing];
        
        [movieWriter setCompletionBlock:^{
            
            WeakSelf(self);
            dispatch_async(dispatch_get_main_queue(), ^{
                
                [self.hud hideAnimated:YES];
                [endFilter removeTarget:movieWriter];
                [movieWriter finishRecording];
                //保存相册
                [self savePhotosAlbum:movieURL];
                
            });
            
        }];
        
        
      });

注：3秒后保存到本地相当于按钮事件，示例而已。movieWriter相当于把视频重写一遍，完成回调后要移除target，还要结束录制。

有什么问题欢迎留言讨论。