CODEWITHSUNDEEP
c#emgucv
Jorge Otero-Millan
Jorge Otero-Millan

Reputation: 49

Converting from VectorOfPoint to VectorOfPointF for contours in Emgu

I am trying to find the convex hull of a contour with emgu 3.1

It seems to be the case that FindContours only accepts a vectorOfVectorOfPoints (not pointsF). But then, convexhull requires a vectorOfPointF. Am I wrong? If I change contours to VectorOfVectorOfPointF I get a runtime error in the call to FindContours.

How do you convert a VectorOfPoint to VectorOfPointF? Is there a better way to do it?

Thanks!

using (var contours = new VectorOfVectorOfPoint())
using (Mat hierachy = new Mat())
{

    CvInvoke.FindContours(img, contours, hierachy, Emgu.CV.CvEnum.RetrType.External, Emgu.CV.CvEnum.ChainApproxMethod.ChainApproxSimple, new Point());
            for (int i = 0; i < contours.Size; i++)
            {
                var contour = contours[i];
                var c = new VectorOfPointF();
                CvInvoke.ConvexHull(contour, c, false, true);
            }

Upvotes: 1

Views: 3417

Answers (2)

digitalhigh
digitalhigh

Reputation: 52

A slighty updated version of @Atresmo's answer. We can just cast the Point to a PointF:

for (int i = 0; i < contours.Size; i++)
{
    var contour = contours[i];
    var vf = new PointF[contour.Size];
    for (int ii = 0; ii < contour.Size; ii++) vf[i] = contour[ii];
    VectorOfPointF vvf = new VectorOfPointF(vf);
    var c = new VectorOfPointF();
    CvInvoke.ConvexHull(vvf, c, false, true);
}

Upvotes: 0

Atresmo
Atresmo

Reputation: 43

It seems that the only way is to construct your VectorOfPointF from each of the VectorOfPoint in the contours object:

for (int i = 0; i < contours.Size; i++)
{
    var contour = contours[i];
    var vf = new PointF[vp.Size];
    for (int ii = 0; ii < contour.Size; ii++) vf[i] = new PointF(contour[ii].X, contour[ii].Y);
    VectorOfPointF vvf = new VectorOfPointF(vf);
    var c = new VectorOfPointF();
    CvInvoke.ConvexHull(vvf, c, false, true);
}

Upvotes: 2

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