public static Polygon Union(Canvas canvas, Polygon window, Polygon subject)
{
Point startPoint;
POLYGON startPolygon;
FindAndOrderPoints(window, subject, out startPoint, out startPolygon);
if (startPoint.X == int.MaxValue)
{
return(window.minX < subject.minX ? window : subject);
}
Point currentPoint = startPoint;
POLYGON currentPolygon = startPolygon;
Polygon polygon = new Polygon(canvas);
do
{
polygon.AddVertex(currentPoint.X, currentPoint.Y);
if (currentPolygon == POLYGON.WINDOW)
{
currentPolygon = currentPoint.CrossPoint ? POLYGON.SUBJECT : POLYGON.WINDOW;
currentPoint = currentPoint.CrossPoint ? currentPoint.SubjectNext : currentPoint.WindowNext;
}
else
{
currentPolygon = currentPoint.CrossPoint ? POLYGON.WINDOW : POLYGON.SUBJECT;
currentPoint = currentPoint.CrossPoint ? currentPoint.WindowNext : currentPoint.SubjectNext;
}
} while (currentPoint != startPoint); //end do while there are more points
polygon.ClosePolygon();
return(polygon);
}
private static void FindAndOrderPoints(Polygon window, Polygon subject,
out Point startPoint, out POLYGON startPolygon)
{
startPolygon = POLYGON.WINDOW;
startPoint = new Point(int.MaxValue, int.MaxValue, false);
WindowPointList windowPoints = new WindowPointList();
SubjectPointList subjectPoints = new SubjectPointList();
Dictionary <Edge, List <Point> > edgeCrossPoints = FindPoints(window, subject);
foreach (Edge windowEdge in window.Edges)
{
Point vertexPoint = new Point(windowEdge.V1.X, windowEdge.V1.Y, false);
if (vertexPoint.X < startPoint.X)
{
startPoint = vertexPoint;
startPolygon = POLYGON.WINDOW;
}
windowPoints.Add(vertexPoint);
edgeCrossPoints[windowEdge].Sort((p1, p2) =>
{
return(Math.Abs(p1.X - windowEdge.V1.X) - Math.Abs(p2.X - windowEdge.V1.X));
});
foreach (Point point in edgeCrossPoints[windowEdge])
{
windowPoints.Add(point);
}
}
foreach (Edge subjectEdge in subject.Edges)
{
Point vertexPoint = new Point(subjectEdge.V1.X, subjectEdge.V1.Y, false);
if (vertexPoint.X < startPoint.X)
{
startPoint = vertexPoint;
startPolygon = POLYGON.SUBJECT;
}
subjectPoints.Add(vertexPoint);
edgeCrossPoints[subjectEdge].Sort((p1, p2) =>
{
return(Math.Abs(p1.X - subjectEdge.V1.X) - Math.Abs(p2.X - subjectEdge.V1.X));
});
foreach (Point point in edgeCrossPoints[subjectEdge])
{
subjectPoints.Add(point);
}
}
}
