Added optimized implementation of PixelAccessor<TColor, TPacked> for Color.

src/ImageSharp/Colors/ColorPixelAccessor.cs

@@ -0,0 +1,98 @@
+// <copyright file="ColorPixelAccessor.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp
+{
+    using System;
+    using System.Runtime.CompilerServices;
+
+    public unsafe sealed class ColorPixelAccessor : PixelAccessor<Color, uint>
+    {
+        public ColorPixelAccessor(ImageBase<Color, uint> image)
+          : base(image)
+        {
+        }
+
+        protected override void CopyFromBGR(PixelRow<Color, uint> row, int targetY, int width)
+        {
+            byte* source = row.DataPointer;
+            byte* destination = this.GetRowPointer(targetY);
+
+            for (int x = 0; x < width; x++)
+            {
+                Unsafe.Write(destination, (uint)(*(source + 2) << 24 | *(source + 1) << 16 | *source << 8 | 255));
+
+                source += 3;
+                destination += 4;
+            }
+        }
+
+        protected override void CopyFromBGRA(PixelRow<Color, uint> row, int targetY, int width)
+        {
+            byte* source = row.DataPointer;
+            byte* destination = this.GetRowPointer(targetY);
+
+            for (int x = 0; x < width; x++)
+            {
+                Unsafe.Write(destination, (uint)(*(source + 2) << 24 | *(source + 1) << 16 | *source << 8 | *(source + 3)));
+
+                source += 4;
+                destination += 4;
+            }
+        }
+
+        protected override void CopyToBGR(PixelRow<Color, uint> row, int sourceY, int width)
+        {
+            byte* source = this.GetRowPointer(sourceY);
+            byte* destination = row.DataPointer;
+
+            for (int x = 0; x < width; x++)
+            {
+                if (BitConverter.IsLittleEndian)
+                {
+                    *destination = *(source + 1);
+                    *(destination + 1) = *(source + 2);
+                    *(destination + 2) = *(source + 3);
+                }
+                else
+                {
+                    *destination = *(source + 3);
+                    *(destination + 1) = *(source + 2);
+                    *(destination + 2) = *(source + 1);
+                }
+
+                source += 4;
+                destination += 3;
+            }
+        }
+
+        protected override void CopyToBGRA(PixelRow<Color, uint> row, int sourceY, int width)
+        {
+            byte* source = this.GetRowPointer(sourceY);
+            byte* destination = row.DataPointer;
+
+            for (int x = 0; x < width; x++)
+            {
+                if (BitConverter.IsLittleEndian)
+                {
+                    *destination = *(source + 1);
+                    *(destination + 1) = *(source + 2);
+                    *(destination + 2) = *(source + 3);
+                    *(destination + 3) = *source;
+                }
+                else
+                {
+                    *destination = *source;
+                    *(destination + 1) = *(source + 3);
+                    *(destination + 2) = *(source + 2);
+                    *(destination + 3) = *(source + 1);
+                }
+
+                source += 4;
+                destination += 4;
+            }
+        }
+    }
+}

src/ImageSharp/Image.cs

@@ -56,5 +56,11 @@ namespace ImageSharp
             : base(other)
         {
         }
+
+        /// <inheritdoc />
+        public override PixelAccessor<Color, uint> Lock()
+        {
+            return new ColorPixelAccessor(this);
+        }
     }
 }

src/ImageSharp/Image/ImageBase.cs

@@ -146,7 +146,7 @@ namespace ImageSharp
         }
 
         /// <inheritdoc/>
-        public PixelAccessor<TColor, TPacked> Lock()
+        public virtual PixelAccessor<TColor, TPacked> Lock()
         {
             return new PixelAccessor<TColor, TPacked>(this);
         }