Question

我目前正在尝试使用Emgu.CV库中的Fisheye.Calibrate方法和Fisheye.UndistorImage方法。据我所知，“校准”方法用于计算相机矩阵（K）和失真矢量（D），它们将用于使用UndistorImage方法使鱼眼图像失真。但是，当我使用这两种方法时，结果并不令人信服。这是我正在测试的输入图像：fisheye input image，结果是：fisheye output image。

当我尝试通过查看对象的数据变量来查看K和D的值时，它对K和D均表示“空”。因此，我不确定是否正在使用Calibrate（）方法正确。我的代码如下：

private void EmguCVUndistortFisheye()
    {
        string[] fileNames = Directory.GetFiles(@"C:\Users\Test\Desktop\Jakob\ImageAnalysis\Images\Calibration", "*.png");
        Size patternSize = new Size(6, 8);
        VectorOfVectorOfPoint3D32F objPoints = new VectorOfVectorOfPoint3D32F();
        VectorOfVectorOfPointF imagePoints = new VectorOfVectorOfPointF();
        foreach (string file in fileNames)
        {
            Mat img = CvInvoke.Imread(file, ImreadModes.Grayscale);
            CvInvoke.Imshow("input", img);
            VectorOfPointF corners = new VectorOfPointF(patternSize.Width * patternSize.Height);
            bool find = CvInvoke.FindChessboardCorners(img, patternSize, corners);
            if (find)
            {
                MCvPoint3D32f[] points = new MCvPoint3D32f[patternSize.Width * patternSize.Height];
                int loopIndex = 0;
                for (int i = 0; i < patternSize.Height; i++)
                {
                    for (int j = 0; j < patternSize.Width; j++)
                        points[loopIndex++] = new MCvPoint3D32f(j, i, 0);
                }
                objPoints.Push(new VectorOfPoint3D32F(points));
                imagePoints.Push(corners);
            }
        }
        Size imageSize = new Size(1280, 1024);
        Mat K = new Mat();
        Mat D = new Mat();
        Mat rotation = new Mat();
        Mat translation = new Mat();
        Fisheye.Calibrate(
            objPoints,
            imagePoints,
            imageSize,
            K,
            D,
            rotation,
            translation,
            Fisheye.CalibrationFlag.CheckCond,
            new MCvTermCriteria(30, 0.1)
        );

        foreach (string file in fileNames)
        {
            Mat img = CvInvoke.Imread(file, ImreadModes.Grayscale);
            Mat output = img.Clone();
            Fisheye.UndistorImage(img, output, K, D);
            CvInvoke.Imshow("output", output);
        }
    }

出现奇怪结果的原因是由于Calibrate方法的参数错误导致，还是仅仅是由于未使用足够的输入图像？

Answer 1

这看起来与我最近在尝试将Mat传递到校准函数时需要Matrix时遇到的问题类似，就像您发现的那样，如果没有报告任何错误。我认为您需要以下条件：

var K = new Matrix<double>(3, 3);
var D = new Matrix<double>(4, 1);

还请注意，如果要检索传入Mat的旋转和平移矢量，则很好，但如果要对其进行计算，则可能需要转换回Matrix 。我只是使用普通的相机校准而不是鱼眼镜头，但以下工作代码片段可能对理解这一点有用：

var cameraMatrix = new Matrix<double>(3, 3);
var distortionCoeffs = new Matrix<double>(4, 1);
var termCriteria = new MCvTermCriteria(30, 0.1);
System.Drawing.PointF[][] imagePoints = imagePointsList.Select(p => p.ToArray()).ToArray();
MCvPoint3D32f[][] worldPoints = worldPointsList.Select(p => p.ToArray()).ToArray();
double error = CvInvoke.CalibrateCamera(worldPoints, imagePoints, imageSize, cameraMatrix, distortionCoeffs, CalibType.RationalModel, termCriteria, out Mat[] rotationVectors, out Mat[] translationVectors);
var rotation = new Matrix<double>(rotationVectors[0].Rows, rotationVectors[0].Cols, rotationVectors[0].DataPointer);
var translation = new Matrix<double>(translationVectors[0].Rows, translationVectors[0].Cols, translationVectors[0].DataPointer);

Emgu.CV Fisheye.Calibrate方法

1 个答案: