added EllipticalArcLineSegment

Author: derBobo

src/ImageSharp.Drawing/Shapes/EllipticalArcLineSegment.cs

@@ -0,0 +1,132 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Collections.Generic;
+using System.Numerics;
+
+namespace SixLabors.ImageSharp.Drawing.Shapes
+{
+    /// <summary>
+    /// Represents a line segment that contains radii and angles that will be rendered as a elliptical arc
+    /// </summary>
+    /// <seealso cref="ILineSegment" />
+    public sealed class EllipticalArcLineSegment : ILineSegment
+    {
+        private const float MinimumSqrDistance = 1.75f;
+        private readonly PointF[] linePoints;
+        private PointF center;
+        private float firstRadius;
+        private float secondRadius;
+        private float rotation;
+        private float startAngle;
+        private float sweepAngle;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EllipticalArcLineSegment"/> class.
+        /// </summary>
+        /// <param name="center"> The center point of the ellipsis that the arc is a part of</param>
+        /// <param name="firstRadius">First radius of the ellipsis</param>
+        /// <param name="secondRadius">Second radius of the ellipsis</param>
+        /// <param name="rotation">The rotation of First radius to the X-Axis</param>
+        /// <param name="startAngle">The Start angle of the ellipsis</param>
+        /// <param name="sweepAngle"> The sweeping angle of the arc</param>
+        public EllipticalArcLineSegment(PointF center, float firstRadius, float secondRadius, float rotation, float startAngle, float sweepAngle)
+        {
+            Guard.MustBeGreaterThan(firstRadius, 0, nameof(firstRadius));
+            Guard.MustBeGreaterThan(secondRadius, 0, nameof(secondRadius));
+            Guard.MustBeBetweenOrEqualTo(rotation, 0, 360, nameof(rotation));
+            Guard.MustBeBetweenOrEqualTo(startAngle, 0, 360, nameof(startAngle));
+            Guard.MustBeBetweenOrEqualTo(sweepAngle, 0, 360, nameof(sweepAngle));
+            this.center = center;
+            this.firstRadius = firstRadius;
+            this.secondRadius = secondRadius;
+            this.rotation = rotation;
+            this.startAngle = startAngle;
+            this.sweepAngle = sweepAngle;
+            this.linePoints = this.GetDrawingPoints();
+            this.EndPoint = this.linePoints[this.linePoints.Length - 1];
+        }
+
+        /// <summary>
+        /// Gets the end point.
+        /// </summary>
+        /// <value>
+        /// The end point.
+        /// </value>
+        public PointF EndPoint { get; }
+
+        /// <summary>
+        /// Transforms the current LineSegment using specified matrix.
+        /// </summary>
+        /// <param name="matrix">The matrix.</param>
+        /// <returns>A line segment with the matrix applied to it.</returns>
+        public EllipticalArcLineSegment Transform(Matrix3x2 matrix)
+        {
+            if (matrix.IsIdentity)
+            {
+                return this;
+            }
+
+            // TODO
+        }
+
+        /// <summary>
+        /// Transforms the current LineSegment using specified matrix.
+        /// </summary>
+        /// <param name="matrix">The matrix.</param>
+        /// <returns>A line segment with the matrix applied to it.</returns>
+        ILineSegment ILineSegment.Transform(Matrix3x2 matrix) => this.Transform(matrix);
+
+        private PointF[] GetDrawingPoints()
+        {
+            var points = new List<PointF>();
+
+            float startX = (float)((this.firstRadius * Math.Sin(Math.PI * this.startAngle / 180) * Math.Cos(Math.PI * this.rotation / 180)) - (this.secondRadius * Math.Cos(Math.PI * this.startAngle / 180) * Math.Sin(Math.PI * this.rotation / 180)) + this.center.X);
+            float startY = (float)((this.firstRadius * Math.Sin(Math.PI * this.startAngle / 180) * Math.Sin(Math.PI * this.rotation / 180)) + (this.secondRadius * Math.Cos(Math.PI * this.startAngle / 180) * Math.Cos(Math.PI * this.rotation / 180)) + this.center.Y);
+            points.Add(new PointF(startX, startY));
+            for (float i = this.startAngle; i < this.startAngle + this.sweepAngle; i++)
+            {
+                float end = i + 1;
+                if (end <= this.startAngle + this.sweepAngle)
+                {
+                    end = this.startAngle + this.sweepAngle;
+                }
+
+                points.AddRange(this.GetDrawingPoints(points[points.Count - 1], i, end));
+            }
+
+            return points.ToArray();
+        }
+
+        private List<PointF> GetDrawingPoints(PointF start, float startAngle, float end)
+        {
+            var points = new List<PointF>();
+            float endX = (float)((this.firstRadius * Math.Sin(Math.PI * end / 180) * Math.Cos(Math.PI * this.rotation / 180)) - (this.secondRadius * Math.Cos(Math.PI * end / 180) * Math.Sin(Math.PI * this.rotation / 180)) + this.center.X);
+            float endY = (float)((this.firstRadius * Math.Sin(Math.PI * end / 180) * Math.Sin(Math.PI * this.rotation / 180)) + (this.secondRadius * Math.Cos(Math.PI * end / 180) * Math.Cos(Math.PI * this.rotation / 180)) + this.center.Y);
+            if ((new Vector2(endX, endY) - new Vector2(start.X, start.Y)).LengthSquared() < MinimumSqrDistance)
+            {
+                points.Add(new PointF(endX, endY));
+            }
+            else
+            {
+                float mid = startAngle + ((startAngle - end) / 2);
+                points.AddRange(this.GetDrawingPoints(start, startAngle, mid));
+                points.AddRange(this.GetDrawingPoints(points[points.Count - 1], mid, end));
+            }
+
+            return points;
+        }
+
+        /// <summary>
+        /// Returns the current <see cref="ILineSegment" /> a simple linear path.
+        /// </summary>
+        /// <returns>
+        /// Returns the current <see cref="ILineSegment" /> as simple linear path.
+        /// </returns>
+        public ReadOnlyMemory<PointF> Flatten()
+        {
+            return this.linePoints;
+        }
+    }
+}