如何将 CIFilter 输出到摄像机视图

Question

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。我让相机输出与AVFoundation框架一起工作。现在，我正在尝试连接 Core 映像框架，但不知道如何连接，Apple 文档让我感到困惑，在线搜索指南和教程没有结果。提前感谢您的帮助。

#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

Answer 1

这里有一些东西可以帮助你开始。这是以下链接中代码的更新版本。

https://gist.github.com/eladb/9662102

诀窍是使用 AVCaptureVideoDataOutputSampleBufferDelegate .
使用此委托，可以使用imageWithCVPixelBuffer从相机缓冲区构造CIImage。

现在，尽管我正在努力弄清楚如何减少滞后。我会尽快更新。

---

更新：延迟现在最小，并且在某些效果上不明显。不幸的是，模糊似乎是最慢的之一。您可能想研究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;
}