GPUimage實時濾鏡的實現

　　GPUIMAGE中GPUImageStillCamera可以調用系統相機，並實現實時濾鏡，但是我沒有找到相機全屏的方法，望知道的說一下

GPUImageStillCamera繼承自GPUImageVideoCamera類，添加了捕獲照片的功能。

GPUImageVideoCamera

初始化方法：

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

sessionPreset是相機拍攝時的解析度。它的值如下

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

cameraPosition相機設備，分為前後 

AVCaptureDevicePositionFront
AVCaptureDevicePositionBack

- (void)startCameraCapture;開始捕獲

- (void)stopCameraCapture;停止捕獲

- (void)rotateCamera;切換前後攝像頭

　　添加實時濾鏡

定義GPUImageStillCamera對象

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

定義要應用的濾鏡

_mFilter = [[FWAmaroFilter alloc] init];

 定義GPUImageView對象，將GPUImageStillCamera對象捕獲的圖像列印在GPUImageView的層。

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

添加濾鏡

    [_mCamera addTarget:_mFilter];

添加顯示

    [_mFilter addTarget:_mGPUImgView];

開始捕獲

    [_mCamera startCameraCapture];

    [self.view addSubview:_mGPUImgView];

到此為止。實時濾鏡已經實現

實現拍照

-(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) {
            
        }];
    }];
}