iOS自定义相机（拍照），出现了一个bug

Question

这个bug看起来很偶然，我不知道怎么解决，请帮帮我， 主要代码在这里：

如果您想查看完整的项目，可以查看此链接 https://github.com/liman123/custom-camera

错误是：当我拍照时，屏幕变成了这张照片，这张照片被扭曲了！

- (void)setupConfiguration
{
_captureSession = [[AVCaptureSession alloc]init];
_captureSession.sessionPreset = AVCaptureSessionPresetPhoto;

_capturedImageView = [[UIImageView alloc]init];
_capturedImageView.frame = self.view.frame; // just to even it out
_capturedImageView.backgroundColor = [UIColor clearColor];
_capturedImageView.userInteractionEnabled = YES;
_capturedImageView.contentMode = UIViewContentModeScaleAspectFill;

_captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc]initWithSession:_captureSession];
_captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
_captureVideoPreviewLayer.frame = self.view.bounds;
[self.view.layer addSublayer:_captureVideoPreviewLayer];

NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
if (devices.count > 0) {
    _captureDevice = devices[0];

    NSError *error = nil;
    AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:_captureDevice error:&error];

    [_captureSession addInput:input];

    _stillImageOutput = [[AVCaptureStillImageOutput alloc]init];
    NSDictionary * outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys: AVVideoCodecJPEG, AVVideoCodecKey, nil];
    [_stillImageOutput setOutputSettings:outputSettings];
    [_captureSession addOutput:_stillImageOutput];
}
}

-(void)captureButtonClick
{
_isCapturingImage = YES;
AVCaptureConnection *videoConnection = nil;
for (AVCaptureConnection *connection in _stillImageOutput.connections)
{
    for (AVCaptureInputPort *port in [connection inputPorts])
    {
        if ([[port mediaType] isEqual:AVMediaTypeVideo] )
        {
            videoConnection = connection;
            break;
        }
    }
    if (videoConnection) {
        break;
    }
}

[_stillImageOutput captureStillImageAsynchronouslyFromConnection:videoConnection completionHandler: ^(CMSampleBufferRef imageSampleBuffer, NSError *error) {

    if (imageSampleBuffer) {

        NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageSampleBuffer];
        UIImage *capturedImage = [[UIImage alloc]initWithData:imageData scale:1];
        _isCapturingImage = NO;
        _capturedImageView.image = capturedImage;
        _selectedImage = capturedImage;
        imageData = nil;

        [self.view addSubview:_imageSelectedView];
    }
}];
}