CODEWITHSUNDEEP
c#opencvemgucv
ss_mj
ss_mj

Reputation: 167

EmguCV PCACompute InputData - Convert VectorOfPoint to Mat

The CvInvoke.PCACompute method expects a IInputArray of data, to do the analysis.

I tried using the source image as the input Mat, but the eigenvectors computed are abnormal, as per my understanding. And I am not able to convert my Contour VectorOfPoint to Mat, which can me fed.

I could also not find a good literature online about implementing PCA Analysis in EmguCV / C#.

Can someone please point me in the right direction.

Below is my code -

public static void getOrientation(Image<Gray,byte> inputImage)
        {
            Image<Gray, Byte> cannyGray = inputImage.Canny(85, 255);

            VectorOfVectorOfPoint contours = new VectorOfVectorOfPoint();
            Mat eigen_vectors = new Mat(inputImage.Size,DepthType.Cv8U,1);
            Mat mean_mat = new Mat(inputImage.Size, DepthType.Cv8U, 1);

            CvInvoke.FindContours(cannyGray, contours, null, RetrType.External, ChainApproxMethod.ChainApproxSimple);

            Point[][] cont_points = contours.ToArrayOfArray();
            Mat contour_mat = new Mat();
            contour_mat.SetTo(cont_points[0]);
            
            //CvInvoke.PCACompute(cannyGray.Mat, mean_mat, eigen_vectors,2);
            CvInvoke.PCACompute(contours, mean_mat, eigen_vectors);

        }

Upvotes: 0

Views: 326

Answers (1)

erik7854
erik7854

Reputation: 170

You have to convert each of your contour to a Mat containing your coordinates.

Here is an example of how you can do it:

// points are the point of one contour
var pointList = points.ToArray();
// use DepthType.Cv64F to allow numbers > 255
Mat dataPoints = new Mat(pointList.Length, 2, DepthType.Cv64F, 1);
double[] pointsData = new double[((int)dataPoints.Total * dataPoints.NumberOfChannels)];
// store the points coordinates in the Mat
for (int i = 0; i < dataPoints.Rows; i++)
{
    pointsData[i * dataPoints.Cols] = pointList[i].X;
    pointsData[i * dataPoints.Cols + 1] = pointList[i].Y;
}
// set the Mat to dataPointsData values
dataPoints.SetTo(pointsData);

// compute PCA
Mat mean = new Mat();
Mat eigenvectors = new Mat();
Mat eigenvalues = new Mat();
CvInvoke.PCACompute(dataPoints, mean, eigenvectors);

Upvotes: 1

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