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(, , , )];
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) {
}];
}];
}