/// <summary>
/// Perform Delaunay triangulation on a given set of landmark points.
/// </summary>
/// <param name="points">The landmark points to use for triangulation.</param>
/// <returns>A list of Triangle structures that each refer to a single triangle of landmark points.</returns>
public static IEnumerable <Triangle> GetDelaunayTriangles(IEnumerable <Point> points)
{
var result = new List <Triangle>();
// calculate the bounding box around the points
var rect = Cv2.BoundingRect(points);
rect.Inflate(10, 10);
// the Subdiv2D class handles Delaunay triangulation
// first we add all points, and then start triangulation
Vec6f[] triangles;
using (var subdiv = new Subdiv2D(rect))
{
foreach (var p in points)
{
var cv_p = new OpenCvSharp.Point2f(p.X, p.Y);
subdiv.Insert(cv_p);
}
triangles = subdiv.GetTriangleList();
}
// return result as an enumeration of triangle structs
return(from t in triangles
let p1 = new Point(t[0], t[1])
let p2 = new Point(t[2], t[3])
let p3 = new Point(t[4], t[5])
where rect.Contains(p1) && rect.Contains(p2) && rect.Contains(p3)
select new Triangle(p1, p2, p3));
}
public void GetTriangleList()
{
using var subdiv = new Subdiv2D(new Rect(0, 0, 500, 500));
var points = new[] { new Point2f(300, 100), new Point2f(200, 300), new Point2f(400, 300) };
subdiv.Insert(points[0]);
subdiv.Insert(points[1]);
subdiv.Insert(points[2]);
var triangles = subdiv.GetTriangleList();
Assert.Single(triangles);
var triangleVertices = new[]
{
triangles[0].Item0, triangles[0].Item1, triangles[0].Item2, triangles[0].Item3, triangles[0].Item4, triangles[0].Item5,
};
foreach (var point in points)
{
Assert.Contains(point.X, triangleVertices);
Assert.Contains(point.Y, triangleVertices);
}
}
private static IEnumerable <int[]> GetDelaunayTriangulationIndexes(Rect rect, List <Point2f> points)
{
rect = Cv2.BoundingRect(points).Union(rect);
using (var subdivision = new Subdiv2D(rect))
{
subdivision.Insert(points);
var triangulation = subdivision.GetTriangleList();
foreach (var cell in triangulation)
{
var p1 = new Point2f(cell.Item0, cell.Item1);
var p2 = new Point2f(cell.Item2, cell.Item3);
var p3 = new Point2f(cell.Item4, cell.Item5);
if (rect.Contains(p1) && rect.Contains(p2) && rect.Contains(p3))
{
var indexA = points.IndexOf(p1);
var indexB = points.IndexOf(p2);
var indexC = points.IndexOf(p3);
var indexes = new[] { indexA, indexB, indexC };
yield return(indexes);
}
}
}
}
