好吧,这很有趣,这就是我所做的(老实说,我不知道这是否是“正确”的方式,是否有更有效的方式)。
- 创建一个移动几何体的变换,使分割线位于 Y 轴上。
- 对于几何图形中的每条线 - 如果 X<0 位于左侧,如果 X>0 位于右侧,如果线与 Y 轴相交,则将其分成两条线。
- 使用步骤 1 中的变换的逆变换来变换两个线列表,并从中重建几何。
这是一个 SplitGeometry 方法,它采用一个几何图形和一条由两个点定义的线并返回这两个几何图形:
private void SplitGeometry(Geometry geo, Point pt1, Point pt2, out PathGeometry leftGeo, out PathGeometry rightGeo)
{
double c = 360.0 + 90.0 - (180.0 / Math.PI * Math.Atan2(pt2.Y - pt1.Y, pt2.X - pt1.X));
var t = new TransformGroup();
t.Children.Add(new TranslateTransform(-pt1.X, -pt1.Y));
t.Children.Add(new RotateTransform(c));
var i = t.Inverse;
leftGeo = new PathGeometry();
rightGeo = new PathGeometry();
foreach (var figure in geo.GetFlattenedPathGeometry().Figures)
{
var left = new List<Point>();
var right = new List<Point>();
var lastPt = t.Transform(figure.StartPoint);
foreach (PolyLineSegment segment in figure.Segments)
{
foreach (var currentPtOrig in segment.Points)
{
var currentPt = t.Transform(currentPtOrig);
ProcessLine(lastPt, currentPt, left, right);
lastPt = currentPt;
}
}
ProcessFigure(left, i, leftGeo);
ProcessFigure(right, i, rightGeo);
}
}
private void ProcessFigure(List<Point> points, GeneralTransform transform, PathGeometry geometry)
{
if (points.Count == 0) return;
var result = new PolyLineSegment();
var prev = points[0];
for (int i = 1; i < points.Count; ++i)
{
var current = points[i];
if (current == prev) continue;
result.Points.Add(transform.Transform(current));
prev = current;
}
if (result.Points.Count == 0) return;
geometry.Figures.Add(new PathFigure(transform.Transform(points[0]), new PathSegment[] { result }, true));
}
private void ProcessLine(Point pt1, Point pt2, List<Point> left, List<Point> right)
{
if (pt1.X >= 0 && pt2.X >= 0)
{
right.Add(pt1);
right.Add(pt2);
}
else if (pt1.X < 0 && pt2.X < 0)
{
left.Add(pt1);
left.Add(pt2);
}
else if (pt1.X < 0)
{
double c = (Math.Abs(pt1.X) * Math.Abs(pt2.Y - pt1.Y)) / Math.Abs(pt2.X - pt1.X);
double y = pt1.Y + c * Math.Sign(pt2.Y - pt1.Y);
var p = new Point(0, y);
left.Add(pt1);
left.Add(p);
right.Add(p);
right.Add(pt2);
}
else
{
double c = (Math.Abs(pt1.X) * Math.Abs(pt2.Y - pt1.Y)) / Math.Abs(pt2.X - pt1.X);
double y = pt1.Y + c * Math.Sign(pt2.Y - pt1.Y);
var p = new Point(0, y);
right.Add(pt1);
right.Add(p);
left.Add(p);
left.Add(pt2);
}
}