GPUimage实时滤镜的实现

　　GPUIMAGE中GPUImageStillCamera可以调用系统相机，并实现实时滤镜，但是我没有找到相机全屏的方法，望知道的说一下

GPUImageStillCamera继承自GPUImageVideoCamera类，添加了捕获照片的功能。

GPUImageVideoCamera

初始化方法：

- (id)initWithSessionPreset:(NSString *)sessionPreset cameraPosition:(AVCaptureDevicePosition)cameraPosition

sessionPreset是相机拍摄时的分辨率。它的值如下

AVCaptureSessionPresetPhoto
AVCaptureSessionPresetHigh
AVCaptureSessionPresetMedium
AVCaptureSessionPresetLow
AVCaptureSessionPreset320x240
AVCaptureSessionPreset352x288
AVCaptureSessionPreset640x480
AVCaptureSessionPreset960x540
AVCaptureSessionPreset1280x720
AVCaptureSessionPreset1920x1080
AVCaptureSessionPreset3840x2160
AVCaptureSessionPresetiFrame960x540
AVCaptureSessionPresetiFrame1280x720
AVCaptureSessionPresetInputPriority

cameraPosition相机设备，分为前后 

AVCaptureDevicePositionFront
AVCaptureDevicePositionBack

- (void)startCameraCapture;开始捕获

- (void)stopCameraCapture;停止捕获

- (void)rotateCamera;切换前后摄像头

　　添加实时滤镜

定义GPUImageStillCamera对象

mCamera = [[GPUImageStillCamera alloc] initWithSessionPreset:AVCaptureSessionPresetPhoto cameraPosition:AVCaptureDevicePositionBack];
    _isBack = YES;
//    _mCamera.horizontallyMirrorRearFacingCamera = NO;
//    _mCamera.horizontallyMirrorFrontFacingCamera = YES;
    _mCamera.outputImageOrientation = UIInterfaceOrientationPortrait;

定义要应用的滤镜

_mFilter = [[FWAmaroFilter alloc] init];

 定义GPUImageView对象，将GPUImageStillCamera对象捕获的图像打印在GPUImageView的层。

    _mGPUImgView = [[GPUImageView alloc]initWithFrame:CGRectMake(0, 0, 320, 426)];

添加滤镜

    [_mCamera addTarget:_mFilter];

添加显示

    [_mFilter addTarget:_mGPUImgView];

开始捕获

    [_mCamera startCameraCapture];

    [self.view addSubview:_mGPUImgView];

到此为止。实时滤镜已经实现

实现拍照

-(void)takePhoto{
    [_mCamera capturePhotoAsJPEGProcessedUpToFilter:_mFilter withCompletionHandler:^(NSData *processedJPEG, NSError *error){
        [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        [[PHAssetCreationRequest creationRequestForAsset] addResourceWithType:PHAssetResourceTypePhoto data:processedJPEG options:nil];
        } completionHandler:^(BOOL success, NSError * _Nullable error) {
            
        }];
    }];
}