使用PointBase代替Point

AIStudio.Wpf.DiagramDesigner/Geometry/EllipseBase.cs

@@ -0,0 +1,60 @@
+using System;
+using System.Collections.Generic;
+
+namespace AIStudio.Wpf.DiagramDesigner.Geometry
+{
+    public class EllipseBase : IShape
+    {
+        public EllipseBase(double cx, double cy, double rx, double ry)
+        {
+            Cx = cx;
+            Cy = cy;
+            Rx = rx;
+            Ry = ry;
+        }
+
+        public double Cx { get; }
+        public double Cy { get; }
+        public double Rx { get; }
+        public double Ry { get; }
+
+        public IEnumerable<PointBase> GetIntersectionsWithLine(LineBase line)
+        {
+            var a1 = line.Start;
+            var a2 = line.End;
+            var dir = new PointBase(line.End.X - line.Start.X, line.End.Y - line.Start.Y);
+            var diff = a1.Substract(Cx, Cy);
+            var mDir = new PointBase(dir.X / (Rx * Rx), dir.Y / (Ry * Ry));
+            var mDiff = new PointBase(diff.X / (Rx * Rx), diff.Y / (Ry * Ry));
+
+            var a = dir.Dot(mDir);
+            var b = dir.Dot(mDiff);
+            var c = diff.Dot(mDiff) - 1.0;
+            var d = b * b - a * c;
+
+            if (d > 0)
+            {
+                var root = Math.Sqrt(d);
+                var ta = (-b - root) / a;
+                var tb = (-b + root) / a;
+
+                if (ta >= 0 && 1 >= ta || tb >= 0 && 1 >= tb)
+                {
+                    if (0 <= ta && ta <= 1)
+                        yield return a1.Lerp(a2, ta);
+
+                    if (0 <= tb && tb <= 1)
+                        yield return a1.Lerp(a2, tb);
+                }
+            }
+            else
+            {
+                var t = -b / a;
+                if (0 <= t && t <= 1)
+                {
+                    yield return a1.Lerp(a2, t);
+                }
+            }
+        }
+    }
+}