Optimize ColorMatrixProcessors

src/ImageSharp/Processing/Processors/ColorMatrix/ColorMatrixProcessor.cs

@@ -7,7 +7,6 @@ namespace ImageSharp.Processing.Processors
 {
     using System;
     using System.Numerics;
-    using System.Runtime.CompilerServices;
     using System.Threading.Tasks;
 
     using ImageSharp.PixelFormats;
@@ -61,29 +60,12 @@ namespace ImageSharp.Processing.Processors
                     this.ParallelOptions,
                     y =>
                         {
-                            int offsetY = y - startY;
+                            Span<TPixel> row = source.GetRowSpan(y - startY);
-                            for (int x = minX; x < maxX; x++)
-                            {
-                                int offsetX = x - startX;
-                                sourcePixels[offsetX, offsetY] = this.ApplyMatrix(sourcePixels[offsetX, offsetY], matrix, compand);
-                            }
-                        });
-            }
-        }
 
-        /// <summary>
+                            for (int x = minX; x < maxX; x++)
-        /// Applies the color matrix against the given color.
-        /// </summary>
-        /// <param name="color">The source color.</param>
-        /// <param name="matrix">The matrix.</param>
-        /// <param name="compand">Whether to compand the color during processing.</param>
-        /// <returns>
-        /// The <see cref="Rgba32"/>.
-        /// </returns>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private TPixel ApplyMatrix(TPixel color, Matrix4x4 matrix, bool compand)
                             {
-            Vector4 vector = color.ToVector4();
+                                ref TPixel pixel = ref row[x - startX];
+                                var vector = pixel.ToVector4();
 
                                 if (compand)
                                 {
@@ -91,9 +73,10 @@ namespace ImageSharp.Processing.Processors
                                 }
 
                                 vector = Vector4.Transform(vector, matrix);
-            TPixel packed = default(TPixel);
+                                pixel.PackFromVector4(compand ? vector.Compress() : vector);
-            packed.PackFromVector4(compand ? vector.Compress() : vector);
+                            }
-            return packed;
+                        });
+            }
         }
     }
 }