ios获取摄像头

 NSError *error = nil;
    
    session = [[AVCaptureSession alloc] init] ;
    
   
    session.sessionPreset = AVCaptureSessionPresetMedium;
    
    AVCaptureDevice *device = [AVCaptureDevice
                               defaultDeviceWithMediaType:AVMediaTypeVideo];//这里默认是使用后置摄像头，你可以改成前置摄像头
    

    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device
                                                                        error:&error];
    if (!input) {
    }
    [session addInput:input];
    
    AVCaptureVideoDataOutput *output = [[AVCaptureVideoDataOutput alloc] init];
    [session addOutput:output];
    
    dispatch_queue_t queue = dispatch_queue_create("myQueue", NULL);
    [output setSampleBufferDelegate:self queue:queue];
 
    output.videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                            [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], kCVPixelBufferPixelFormatTypeKey,
                            [NSNumber numberWithInt: 320], (id)kCVPixelBufferWidthKey,
                            [NSNumber numberWithInt: 240], (id)kCVPixelBufferHeightKey,
                            nil];
    
    AVCaptureVideoPreviewLayer* preLayer = [AVCaptureVideoPreviewLayer layerWithSession: session];

    preLayer.frame = self.view.bounds;
    preLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
    [self.view.layer addSublayer:preLayer];
    output.minFrameDuration = CMTimeMake(1, 15);
    
    [session startRunning];