private void clipBtn_Click(object sender, RoutedEventArgs e)
{
CGPolygon polygon = new CGPolygon(PolygonPoints);
List <CGLine> segments = new List <CGLine>();
foreach (var l in this.Lines)
{
Point a = new Point(l.X1, l.Y1);
Point b = new Point(l.X2, l.Y2);
CGLine S = new CGLine(a, b);
segments.Add(S);
}
List <Point> pList = new List <Point>();
var x = polygon.Clip(segments);
foreach (var item in x)
{
Line ln = new Line();
ln.X1 = item.A.X;
ln.Y1 = item.A.Y;
ln.X2 = item.B.X;
ln.Y2 = item.B.Y;
ln.Stroke = Brushes.Pink;
ln.StrokeThickness = 2;
mainContainer.Children.Add(ln);
}
}
private void Grid_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
switch (DrawingMode)
{
case Mode.Polygon:
Point p = e.GetPosition(mainContainer);
PolygonPoints.Add(p);
if (PolygonPoints.Count > 1)
{
this.PolygonRadioBtn.IsEnabled = true;
}
if (!CGPolygon.PolygonIsConvex(PolygonPoints))
{
MessageBox.Show("Polygon is not convex");
PolygonPoints.Remove(p);
break;
}
var circle = new Ellipse {
Stroke = Brushes.Black,
StrokeThickness = 2,
};
Canvas.SetLeft(circle, p.X - 2);
Canvas.SetTop(circle, p.Y - 2);
mainContainer.Children.Add(circle);
break;
case Mode.DrawLine:
Point lP = e.GetPosition(mainContainer);
break;
}
}
public static bool PolygonIsConvex(List <Point> Points)
{
// For each set of three adjacent points A, B, C,
// find the cross product AB · BC. If the sign of
// all the cross products is the same, the angles
// are all positive or negative (depending on the
// order in which we visit them) so the polygon
// is convex.
bool got_negative = false;
bool got_positive = false;
int num_points = Points.Count;
int B, C;
for (int A = 0; A < num_points; A++)
{
B = (A + 1) % num_points;
C = (B + 1) % num_points;
double cross_product = CGPolygon.CrossProductLength(Points[A].X, Points[A].Y, Points[B].X,
Points[B].Y, Points[C].X, Points[C].Y);
if (cross_product < 0)
{
got_negative = true;
}
else if (cross_product > 0)
{
got_positive = true;
}
if (got_negative && got_positive)
{
return(false);
}
}
// If we got this far, the polygon is convex.
return(true);
}
