Convex Hull in CSharp

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System Requirement

Component Requirement Detail
Emgu CV Version 1.5+
Operation System Cross Platform

Source Code

Emgu CV 3.x

Click to view source code

#region Create some random points
Random r = new Random();
PointF[] pts = new PointF[200];
for (int i = 0; i < pts.Length; i++)
{
   pts[i] = new PointF((float)(100 + r.NextDouble() * 400), (float)(100 + r.NextDouble() * 400));
}
#endregion

Mat img = new Mat(600, 600, DepthType.Cv8U, 3);
img.SetTo(new MCvScalar(255.0, 255.0, 255.0));
//Draw the points 
foreach (PointF p in pts)
   CvInvoke.Circle(img, Point.Round(p), 3, new MCvScalar(0.0, 0.0, 0.0));

//Find and draw the convex hull

Stopwatch watch = Stopwatch.StartNew();
PointF[] hull = CvInvoke.ConvexHull(pts, true);
watch.Stop();
CvInvoke.Polylines(
   img,
#if NETFX_CORE
   Extensions.ConvertAll<PointF, Point>(hull, Point.Round),
#else
   Array.ConvertAll<PointF, Point>(hull, Point.Round),
#endif
   true, new MCvScalar(255.0, 0.0, 0.0));

Emgu.CV.UI.ImageViewer.Show(img, String.Format("Convex Hull Computed in {0} milliseconds", watch.ElapsedMilliseconds));

Emgu CV 1.x

Click to view source code

#region Create some random points
Random r = new Random();
PointF[] pts = new PointF[200];
for (int i = 0; i < pts.Length; i++)
{
   pts[i] = new PointF((float)(100 + r.NextDouble() * 400), (float)(100 + r.NextDouble() * 400));
}
#endregion

Image<Bgr, Byte> img = new Image<Bgr, byte>(600, 600, new Bgr(255.0, 255.0, 255.0));
//Draw the points 
foreach (PointF p in pts)
   img.Draw(new CircleF(p, 3), new Bgr(0.0, 0.0, 0.0), 1);

//Find and draw the convex hull
using (MemStorage storage = new MemStorage())
{
   Stopwatch watch = Stopwatch.StartNew();
   PointF[] hull = PointCollection.ConvexHull(pts, storage, Emgu.CV.CvEnum.ORIENTATION.CV_CLOCKWISE).ToArray();
   watch.Stop();
   img.DrawPolyline(
       Array.ConvertAll<PointF, Point>(hull, Point.Round),
       true, new Bgr(255.0, 0.0, 0.0), 1);

   ImageViewer.Show(img, String.Format("Convex Hull Computed in {0} milliseconds", watch.ElapsedMilliseconds));
}

Result

ConvexHullExample.png