利用GPUImage自定义相机需要以下几个类：

GPUImageStillCamera  处理相机设置

GPUImageView  图片预览层

GPUImageFilter  相机添加滤镜处理

相机基本设置处理

_myCamera = [[GPUImageStillCamera alloc] initWithSessionPreset:AVCaptureSessionPreset1280x720 cameraPosition:AVCaptureDevicePositionBack];

    //竖屏方向

    _myCamera.outputImageOrientation = UIInterfaceOrientationPortrait;

//滤镜设置(伽玛线样式)

GPUImageGammaFilter *stretchDistortionFilter = [[GPUImageGammaFilter alloc] init]; 

 self.myFilter = stretchDistortionFilter;

//图片预览处理

_imageView = [[GPUImageView alloc] initWithFrame:CGRectMake(0, 0, kScreenW, kScreenH)];

 相机全屏设置

    _imageView.fillMode = kGPUImageFillModeStretch;

//添加滤镜到相机上

    [_myCamera addTarget:stretchDistortionFilter];

    [stretchDistortionFilter addTarget:_imageView];

    [self.view addSubview:_imageView];

    [_myCamera startCameraCapture];

定格一张图片 保存到相册

    [self.myCamera capturePhotoAsPNGProcessedUpToFilter:self.myFilter withCompletionHandler:^(NSData *processedPNG, NSError *error) {

        NSLog(@"error--%@",error);

    }];