[JavaCV]cvApproxPoly Input array is not a valid matrix

Torej probam detektirat pravokotnik, ki je popačen s perspektivo in ga uporabiti za popravek perspektive.

CvSeq corners_seq = cvCreateSeq(0 , Loader.sizeof(CvSeq.class), Loader.sizeof(CvPoint.class), corners_storage);
for (int i = 0; i < table_lines.length; i++)
{
    for (int j = i + 1; j < table_lines.length; j++)
    {
        CvPoint pt = HelperClass.ComputeIntersection(table_lines[i][0],table_lines[i][1], table_lines[j][0],table_lines[j][1]);
        if (pt.x() >= 0 && pt.y() >= 0)
        {
             corners_seq.put(pt);
        }
    }
}
CvMemStorage corners_storage = cvCreateMemStorage(0);
CvSeq corners = cvApproxPoly(corners_seq, corners_seq.header_size(), corners_storage, CV_POLY_APPROX_DP, 8, 0);

corners_seq na koncu vsebuje 4 točke.

Vendar ob klicu cvApproxPoly dobim error OpenCV Error: Bad argument (Input array is not a valid matrix) in unknown function, file ..\..\..\src\opencv\modules\imgproc\src\utils.cpp, line 54
Exception in thread "main" java.lang.RuntimeException: ..\..\..\src\opencv\modules\imgproc\src\utils.cpp:54: error: (-5) Input array is not a valid matrix

at com.googlecode.javacv.cpp.opencv_imgproc.cvApproxPoly(Native Method)

A kdo ve kaj bi blo narobe? Upam da je kak opencv/javacv developer tlele :)