From ec1e4eafaaf991141dd4b6c38af739ca01050cf6 Mon Sep 17 00:00:00 2001
From: Jonas Frost <j@duplo.org>
Date: Wed, 18 May 2016 23:12:20 -0700
Subject: [PATCH] Optimized Rotate() to use pre calculated rotation matrix

Former-commit-id: f54c50b9425657fa4cc899838b96c9f8a6529017
Former-commit-id: 819dd1dc7b3dd5d2824ef07ce39ef8ee791f8d40
Former-commit-id: 721b476e0647f7eb6f2a4e7fff037354215a7e81
---
 src/ImageProcessorCore/Numerics/Point.cs  | 23 +++++++++++++++++++++++
 src/ImageProcessorCore/Samplers/Rotate.cs |  6 +++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/ImageProcessorCore/Numerics/Point.cs b/src/ImageProcessorCore/Numerics/Point.cs
index 370592406..472a1c773 100644
--- a/src/ImageProcessorCore/Numerics/Point.cs
+++ b/src/ImageProcessorCore/Numerics/Point.cs
@@ -158,6 +158,29 @@ namespace ImageProcessorCore
             return new Vector2(this.X, this.Y);
         }
 
+        /// <summary>
+        /// Rotates a point around a given a rotation matrix.
+        /// </summary>
+        /// <param name="point">The point to rotate</param>
+        /// <param name="rotation">Rotation matrix used</param>
+        /// <returns></returns>
+        public static Point Rotate( Point point, Matrix3x2 rotation )
+        {
+            return new Point( Vector2.Transform( point.backingVector, rotation ) );
+        }
+
+        /// <summary>
+        /// Creates a rotation matrix for
+        /// </summary>
+        /// <param name="origion">The origin point to rotate around</param>
+        /// <param name="degrees">Rotation in degrees</param>
+        /// <returns></returns>
+        public static Matrix3x2 CreateRotatation( Point origin, float degrees )
+        {
+            float radians = (float)ImageMaths.DegreesToRadians( degrees );
+            return Matrix3x2.CreateRotation( radians, origin.backingVector );
+        }
+
         /// <summary>
         /// Rotates a point around a given origin by the specified angle in degrees.
         /// </summary>
diff --git a/src/ImageProcessorCore/Samplers/Rotate.cs b/src/ImageProcessorCore/Samplers/Rotate.cs
index b85667730..bc10e2fdb 100644
--- a/src/ImageProcessorCore/Samplers/Rotate.cs
+++ b/src/ImageProcessorCore/Samplers/Rotate.cs
@@ -3,6 +3,8 @@
 // Licensed under the Apache License, Version 2.0.
 // </copyright>
 
+using System.Numerics;
+
 namespace ImageProcessorCore.Samplers
 {
     using System.Threading.Tasks;
@@ -62,6 +64,8 @@ namespace ImageProcessorCore.Samplers
             float widthFactor = source.Width / (float)target.Width;
             float heightFactor = source.Height / (float)target.Height;
 
+            Matrix3x2 rotation = Point.CreateRotatation( centre, negativeAngle );
+
             Parallel.For(
                 startY,
                 endY,
@@ -78,7 +82,7 @@ namespace ImageProcessorCore.Samplers
                             int originX = (int)((x - startX) * widthFactor);
 
                             // Rotate at the centre point
-                            Point rotated = Point.Rotate(new Point(originX, originY), centre, negativeAngle);
+                            Point rotated = Point.Rotate(new Point(originX, originY), rotation);
                             if (sourceRectangle.Contains(rotated.X, rotated.Y))
                             {
                                 target[x, y] = source[rotated.X, rotated.Y];