如何将 CIFilter 输出到相机视图？

我刚刚开始使用 Objective-C，我正在尝试创建一个简单的应用程序，它显示带有模糊效果的相机视图。我得到了与 AVFoundation 框架一起使用的相机输出。现在，我正在尝试连接 Core 图像框架，但不知道如何连接，Apple 文档让我感到困惑，并且在线搜索指南和教程没有结果。先谢谢您的帮助。

#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
@interface ViewController ()

@property (strong ,nonatomic) CIContext *context;

@end

@implementation ViewController
AVCaptureSession *session;
AVCaptureStillImageOutput *stillImageOutput;

-(CIContext *)context
{
    if(!_context)
    {
        _context = [CIContext contextWithOptions:nil];
    }
    return _context;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)viewWillAppear:(BOOL)animated{
    session = [[AVCaptureSession alloc] init];
    [session setSessionPreset:AVCaptureSessionPresetPhoto];

    AVCaptureDevice *inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    NSError *error;
    AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&error];

    if ([session canAddInput:deviceInput]) {
        [session addInput:deviceInput];
    }

    AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
    [previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
    CALayer *rootLayer = [[self view] layer];
    [rootLayer setMasksToBounds:YES];
    CGRect frame = self.imageView.frame;

    [previewLayer setFrame:frame];

    [previewLayer.connection setVideoOrientation:AVCaptureVideoOrientationLandscapeRight];


    [rootLayer insertSublayer:previewLayer atIndex:0];

    stillImageOutput = [[AVCaptureStillImageOutput alloc] init];
    NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [stillImageOutput setOutputSettings:outputSettings];

    [session addOutput:stillImageOutput];

    [session startRunning];     
}
@end

这里有一些可以帮助您入门的东西。这是来自以下链接的代码的更新版本。
https://gist.github.com/eladb/9662102 https://gist.github.com/eladb/9662102

诀窍是使用AVCaptureVideoDataOutputSampleBufferDelegate.
有了这个委托，您可以使用imageWithCVPixelBuffer构建一个CIImage从你的相机缓冲区。

现在我正在尝试找出减少延迟的方法。我会尽快更新。

更新：延迟现在很小，并且对某些影响不明显。不幸的是，模糊似乎是最慢的之一。您可能想了解一下vImage.

#import "ViewController.h"
#import <CoreImage/CoreImage.h>
#import <AVFoundation/AVFoundation.h>

@interface ViewController () {

}

@property (strong, nonatomic) CIContext *coreImageContext;
@property (strong, nonatomic) AVCaptureSession *cameraSession;
@property (strong, nonatomic) AVCaptureVideoDataOutput *videoOutput;
@property (strong, nonatomic) UIView *blurCameraView;
@property (strong, nonatomic) CIFilter *filter;
@property BOOL cameraOpen;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.blurCameraView = [[UIView alloc]initWithFrame:[[UIScreen mainScreen] bounds]];
    [self.view addSubview:self.blurCameraView];

    //setup filter
    self.filter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [self.filter setDefaults];
    [self.filter setValue:@(3.0f) forKey:@"inputRadius"];

    [self setupCamera];
    [self openCamera];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)setupCamera
{
    self.coreImageContext = [CIContext contextWithOptions:@{kCIContextUseSoftwareRenderer : @(YES)}];

    // session
    self.cameraSession = [[AVCaptureSession alloc] init];
    [self.cameraSession setSessionPreset:AVCaptureSessionPresetLow];
    [self.cameraSession commitConfiguration];

    // input
    AVCaptureDevice *shootingCamera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *shootingDevice = [AVCaptureDeviceInput deviceInputWithDevice:shootingCamera error:NULL];
    if ([self.cameraSession canAddInput:shootingDevice]) {
        [self.cameraSession addInput:shootingDevice];
    }

    // video output
    self.videoOutput = [[AVCaptureVideoDataOutput alloc] init];
    self.videoOutput.alwaysDiscardsLateVideoFrames = YES;
    [self.videoOutput setSampleBufferDelegate:self queue:dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0)];
    if ([self.cameraSession canAddOutput:self.videoOutput]) {
        [self.cameraSession addOutput:self.videoOutput];
    }

    if (self.videoOutput.connections.count > 0) {
        AVCaptureConnection *connection = self.videoOutput.connections[0];
        connection.videoOrientation = AVCaptureVideoOrientationPortrait;
    }

    self.cameraOpen = NO;
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);

    // turn buffer into an image we can manipulate
    CIImage *result = [CIImage imageWithCVPixelBuffer:imageBuffer];

    // filter
    [self.filter setValue:result forKey:@"inputImage"];

    // render image
    CGImageRef blurredImage = [self.coreImageContext createCGImage:self.filter.outputImage fromRect:result.extent];
    dispatch_async(dispatch_get_main_queue(), ^{
        self.blurCameraView.layer.contents = (__bridge id)blurredImage;
        CGImageRelease(blurredImage);
    });
}

- (void)openCamera {
    if (self.cameraOpen) {
        return;
    }

    self.blurCameraView.alpha = 0.0f;
    [self.cameraSession startRunning];
    [self.view layoutIfNeeded];

    [UIView animateWithDuration:3.0f animations:^{

        self.blurCameraView.alpha = 1.0f;

    }];

    self.cameraOpen = YES;
}