void CalcConvexHull_Executed(object sender, EventArgs e)
{
UpdateStatusLabel("calculating convex hull...");
//clear old lines
var oldHull = canvas.Geometries.OfType <Segment2d> ().ToArray();
foreach (var l in oldHull)
{
canvas.Geometries.Remove(l);
}
//get all points
var points = canvas.Geometries.OfType <Vector2d> ().ToArray();
watch.Start();
var convexHull = GeoAlgos.MonotoneChainConvexHull(points);
watch.Stop();
//draw convex hull
for (var i = 0; i < convexHull.Length; i++)
{
var next = (i + 1) % convexHull.Length;
canvas.Geometries.Add(new Segment2d(convexHull [i], convexHull [next]));
}
UpdateUi(watch.Duration.TotalSeconds + " ms");
}
/// <summary>
/// Calculates the minimum bounding box.
/// </summary>
/// <param name="points">Bounding Box.</param>
public static Polygon2d Calculate(Vector2d[] points)
{
//calculate the convex hull
var hullPoints = GeoAlgos.MonotoneChainConvexHull(points);
//check if no bounding box available
if (hullPoints.Length <= 1)
{
return new Polygon2d {
Points = hullPoints.ToList()
}
}
;
Rectangle2d minBox = null;
var minAngle = 0d;
//foreach edge of the convex hull
for (var i = 0; i < hullPoints.Length; i++)
{
var nextIndex = i + 1;
var current = hullPoints [i];
var next = hullPoints [nextIndex % hullPoints.Length];
var segment = new Segment2d(current, next);
//min / max points
var top = double.MinValue;
var bottom = double.MaxValue;
var left = double.MaxValue;
var right = double.MinValue;
//get angle of segment to x axis
var angle = AngleToXAxis(segment);
//rotate every point and get min and max values for each direction
foreach (var p in hullPoints)
{
var rotatedPoint = RotateToXAxis(p, angle);
top = Math.Max(top, rotatedPoint.Y);
bottom = Math.Min(bottom, rotatedPoint.Y);
left = Math.Min(left, rotatedPoint.X);
right = Math.Max(right, rotatedPoint.X);
}
//create axis aligned bounding box
var box = new Rectangle2d(new Vector2d(left, bottom), new Vector2d(right, top));
if (minBox == null || minBox.Area() > box.Area())
{
minBox = box;
minAngle = angle;
}
}
//rotate axis algined box back
var minimalBoundingBox = new Polygon2d
{
Points = minBox.Points.Select(p => RotateToXAxis(p, -minAngle)).ToList()
};
return(minimalBoundingBox);
}
