Question

I have the following code fragment:

int count = (int)sizes.size();

CvSeq* seq = cvCreateSeq(0, sizeof(CvSeq), sizeof(CvPoint2D32f), memStorage);
float line[4];

for (int i=0;i<count;i++) {
    CvPoint2D32f p;
    p.x = sizes[i];
    p.y = depths[i];
    cvSeqPush(seq, &p);
}

cvFitLine( seq, CV_DIST_L1, 1, 0.001, 0.001, line );

but this code throws an exception: Unsupported format or combination of formats (Input sequence must consist of 2d points or 3d points) in cvFitLine
Where’s the problem in my code? (I’m new in OpenCV)

Answer 1

Quoting from the documentation of cvCreateSeq concerning the first parameter:

seqFlags – Flags of the created sequence. If the sequence is not passed to any function working with a specific type of sequences, the sequence value may be set to 0, otherwise the appropriate type must be selected from the list of predefined sequence types.

And looking at cvFitLine:

points – Sequence or array of 2D or 3D points with 32-bit integer or floating-point coordinates

So you have to specify the type of points added to the seqeuence.

CvSeq* seq = cvCreateSeq(CV_32FC2, sizeof(CvSeq), sizeof(CvPoint2D32f), memStorage);

Should do the trick.