Fix Convolution2DProcessor

Also inlined ColorMatrix cos I spotted it and couldn't ignore.

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

@@ -7,6 +7,7 @@ namespace ImageSharp.Processing.Processors
 {
     using System;
     using System.Numerics;
+    using System.Runtime.CompilerServices;
     using System.Threading.Tasks;
 
     using ImageSharp.PixelFormats;
@@ -79,6 +80,7 @@ namespace ImageSharp.Processing.Processors
         /// <returns>
         /// The <see cref="Rgba32"/>.
         /// </returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private TPixel ApplyMatrix(TPixel color, Matrix4x4 matrix, bool compand)
         {
             Vector4 vector = color.ToVector4();

src/ImageSharp/Processing/Processors/Convolution/Convolution2DProcessor.cs

@@ -5,7 +5,6 @@
 
 namespace ImageSharp.Processing.Processors
 {
-    using System;
     using System.Numerics;
     using System.Threading.Tasks;
 
@@ -57,10 +56,11 @@ namespace ImageSharp.Processing.Processors
             int maxX = endX - 1;
 
             using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
+            using (PixelAccessor<TPixel> sourcePixels = source.Lock())
             {
-                using (PixelAccessor<TPixel> sourcePixels = source.Lock())
-                {
-                    Parallel.For(
+                sourcePixels.CopyTo(targetPixels);
+
+                Parallel.For(
                     startY,
                     endY,
                     this.ParallelOptions,
@@ -119,7 +119,6 @@ namespace ImageSharp.Processing.Processors
                             targetPixels[x, y] = packed;
                         }
                     });
-                }
 
                 source.SwapPixelsBuffers(targetPixels);
             }