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];