WPF如何检查应用转换时的几何交叉点？

Question

我有几个随机大小的画布对象并应用RenderTransform角度。 内部画布我有几何对象（线）。

我正在使用绑定的宽度和高度来加载父路径画布对象的路径。

<Path x:Name="gem2_Copy" Stretch="Fill" Stroke="Black" Opacity="0.345" RenderTransformOrigin="0.5,0.5" Width="{Binding ActualWidth, ElementName=canvas}" Height="{Binding ActualHeight, ElementName=canvas}"> 
      <Path.Data> 
       <PathGeometry> 
        <PathFigure IsClosed="True" IsFilled="True"> 
         <LineSegment Point="0,0"> 

         </LineSegment> 
         <LineSegment Point="5,5"> 

         </LineSegment> 
         <LineSegment Point="0,5"> 

         </LineSegment>  
        </PathFigure> 
       </PathGeometry>  
      </Path.Data> 

      </Path> 

如何检查的PathFigure与其他道路相交的几何？ 我algoritm检查线交叉，但由于路径分线点我可以不适用它始终是： 0,0 5,5 0,5

，我需要全局坐标。我怎样才能将路径点转换为全局坐标，并考虑到渲染转换角度改变，路径宽度和高度改变？

foreach (var figure in geom.Figures) 
{ 
    foreach (LineSegment segment in figure.Segments) 
    { 
     // I have here 0,0;5,5;0,5 
    } 
} 

Answer 1

已经找到怎么办主要部分：

// Get scale transformation (find scale factor) 
    var w = (gem2_Copy.ActualWidth/gem2_Copy.Data.Bounds.Width); 
    var h = (gem2_Copy.ActualHeight/gem2_Copy.Data.Bounds.Height); 
    var transform = new ScaleTransform(w, h); 

    foreach (var figure in geom.Figures) 
    { 
     foreach (LineSegment segment in figure.Segments) 
     { 
     // Use scale transformation to change geometry points position. 
     var scaled=transform.Transform(segment.Point); 

     // Translate point to screen coordinates (including rotation) 
     var onScreen = canvas.TranslatePoint(scaled, root); 

     // Use line intersection formula 
     } 
    } 

代码，可以找到交集：

public static Vector? Intersects(Point a1, Point a2, Point b1, Point b2) 
    { 
     Vector b = a2 - a1; 
     Vector d = b2 - b1; 
     var bDotDPerp = b.X * d.Y - b.Y * d.X; 

     if (bDotDPerp == 0) 
      return null; 

     Vector c = b1 - a1; 
     var t = (c.X * d.Y - c.Y * d.X)/bDotDPerp; 
     if (t < 0 || t > 1) 
     { 
      return null; 
     } 

     var u = (c.X * b.Y - c.Y * b.X)/bDotDPerp; 
     if (u < 0 || u > 1) 
     { 
      return null; 
     } 

     return new Vector(a1.X, a1.Y) + t * b; 
    }