Optimize Convolution processors

src/ImageSharp/Image/ImageBase{TPixel}.cs

@@ -231,6 +231,15 @@ namespace ImageSharp
             return new PixelAccessor<TPixel>(this);
         }
 
+        /// <summary>
+        /// Copies the pixels to another <see cref="PixelAccessor{TPixel}"/> of the same size.
+        /// </summary>
+        /// <param name="target">The target pixel buffer accessor.</param>
+        internal void CopyTo(PixelAccessor<TPixel> target)
+        {
+            SpanHelper.Copy(this.span, target.PixelBuffer.Span);
+        }
+
         /// <summary>
         /// Switches the buffers used by the image and the PixelAccessor meaning that the Image will "own" the buffer from the PixelAccessor and the PixelAccessor will now own the Images buffer.
         /// </summary>

src/ImageSharp/Image/PixelAccessor{TPixel}.cs

@@ -20,6 +20,13 @@ namespace ImageSharp
     internal sealed class PixelAccessor<TPixel> : IDisposable, IBuffer2D<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
+#pragma warning disable SA1401 // Fields must be private
+        /// <summary>
+        /// The <see cref="Buffer{T}"/> containing the pixel data.
+        /// </summary>
+        internal Buffer2D<TPixel> PixelBuffer;
+#pragma warning restore SA1401 // Fields must be private
+
         /// <summary>
         /// A value indicating whether this instance of the given entity has been disposed.
         /// </summary>
@@ -31,11 +38,6 @@ namespace ImageSharp
         /// </remarks>
         private bool isDisposed;
 
-        /// <summary>
-        /// The <see cref="Buffer{T}"/> containing the pixel data.
-        /// </summary>
-        private Buffer2D<TPixel> pixelBuffer;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelAccessor{TPixel}"/> class.
         /// </summary>
@@ -88,7 +90,7 @@ namespace ImageSharp
         /// <summary>
         /// Gets the pixel buffer array.
         /// </summary>
-        public TPixel[] PixelArray => this.pixelBuffer.Array;
+        public TPixel[] PixelArray => this.PixelBuffer.Array;
 
         /// <summary>
         /// Gets the size of a single pixel in the number of bytes.
@@ -116,7 +118,7 @@ namespace ImageSharp
         public ParallelOptions ParallelOptions { get; }
 
         /// <inheritdoc />
-        Span<TPixel> IBuffer2D<TPixel>.Span => this.pixelBuffer;
+        Span<TPixel> IBuffer2D<TPixel>.Span => this.PixelBuffer;
 
         private static PixelOperations<TPixel> Operations => PixelOperations<TPixel>.Instance;
 
@@ -156,7 +158,7 @@ namespace ImageSharp
             // Note disposing is done.
             this.isDisposed = true;
 
-            this.pixelBuffer.Dispose();
+            this.PixelBuffer.Dispose();
 
             // This object will be cleaned up by the Dispose method.
             // Therefore, you should call GC.SuppressFinalize to
@@ -171,7 +173,7 @@ namespace ImageSharp
         /// </summary>
         public void Reset()
         {
-            this.pixelBuffer.Clear();
+            this.PixelBuffer.Clear();
         }
 
         /// <summary>
@@ -243,7 +245,7 @@ namespace ImageSharp
         /// <remarks>If <see cref="M:PixelAccessor.PooledMemory"/> is true then caller is responsible for ensuring <see cref="M:PixelDataPool.Return()"/> is called.</remarks>
         internal TPixel[] ReturnCurrentColorsAndReplaceThemInternally(int width, int height, TPixel[] pixels)
         {
-            TPixel[] oldPixels = this.pixelBuffer.TakeArrayOwnership();
+            TPixel[] oldPixels = this.PixelBuffer.TakeArrayOwnership();
             this.SetPixelBufferUnsafe(width, height, pixels);
             return oldPixels;
         }
@@ -254,7 +256,7 @@ namespace ImageSharp
         /// <param name="target">The target pixel buffer accessor.</param>
         internal void CopyTo(PixelAccessor<TPixel> target)
         {
-            SpanHelper.Copy(this.pixelBuffer.Span, target.pixelBuffer.Span);
+            SpanHelper.Copy(this.PixelBuffer.Span, target.PixelBuffer.Span);
         }
 
         /// <summary>
@@ -425,7 +427,7 @@ namespace ImageSharp
         /// <param name="pixels">The pixel buffer</param>
         private void SetPixelBufferUnsafe(int width, int height, Buffer2D<TPixel> pixels)
         {
-            this.pixelBuffer = pixels;
+            this.PixelBuffer = pixels;
 
             this.Width = width;
             this.Height = height;

src/ImageSharp/Memory/SpanHelper.cs

@@ -70,7 +70,7 @@ namespace ImageSharp.Memory
         public static void Copy<T>(Span<T> source, Span<T> destination)
             where T : struct
         {
-            Copy(source, destination, source.Length);
+            Copy(source, destination, Math.Min(source.Length, destination.Length));
         }
 
         /// <summary>

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

@@ -5,6 +5,7 @@
 
 namespace ImageSharp.Processing.Processors
 {
+    using System;
     using System.Numerics;
     using System.Threading.Tasks;
 
@@ -56,10 +57,9 @@ namespace ImageSharp.Processing.Processors
             int maxY = endY - 1;
             int maxX = endX - 1;
 
-            using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
-            using (PixelAccessor<TPixel> sourcePixels = source.Lock())
+            using (var targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
             {
-                sourcePixels.CopyTo(targetPixels);
+                source.CopyTo(targetPixels);
 
                 Parallel.For(
                     startY,
@@ -67,6 +67,9 @@ namespace ImageSharp.Processing.Processors
                     this.ParallelOptions,
                     y =>
                     {
+                        Span<TPixel> sourceRow = source.GetRowSpan(y);
+                        Span<TPixel> targetRow = targetPixels.GetRowSpan(y);
+
                         for (int x = startX; x < endX; x++)
                         {
                             float rX = 0;
@@ -83,6 +86,7 @@ namespace ImageSharp.Processing.Processors
                                 int offsetY = y + fyr;
 
                                 offsetY = offsetY.Clamp(0, maxY);
+                                Span<TPixel> sourceOffsetRow = source.GetRowSpan(offsetY);
 
                                 for (int fx = 0; fx < kernelXWidth; fx++)
                                 {
@@ -90,8 +94,7 @@ namespace ImageSharp.Processing.Processors
                                     int offsetX = x + fxr;
 
                                     offsetX = offsetX.Clamp(0, maxX);
-
-                                    Vector4 currentColor = sourcePixels[offsetX, offsetY].ToVector4();
+                                    var currentColor = sourceOffsetRow[offsetX].ToVector4();
 
                                     if (fy < kernelXHeight)
                                     {
@@ -115,9 +118,8 @@ namespace ImageSharp.Processing.Processors
                             float green = MathF.Sqrt((gX * gX) + (gY * gY));
                             float blue = MathF.Sqrt((bX * bX) + (bY * bY));
 
-                            TPixel packed = default(TPixel);
-                            packed.PackFromVector4(new Vector4(red, green, blue, sourcePixels[x, y].ToVector4().W));
-                            targetPixels[x, y] = packed;
+                            ref TPixel pixel = ref targetRow[x];
+                            pixel.PackFromVector4(new Vector4(red, green, blue, sourceRow[x].ToVector4().W));
                         }
                     });
 

src/ImageSharp/Processing/Processors/Convolution/Convolution2PassProcessor.cs

@@ -46,7 +46,7 @@ namespace ImageSharp.Processing.Processors
             int width = source.Width;
             int height = source.Height;
 
-            using (PixelAccessor<TPixel> firstPassPixels = new PixelAccessor<TPixel>(width, height))
+            using (var firstPassPixels = new PixelAccessor<TPixel>(width, height))
             using (PixelAccessor<TPixel> sourcePixels = source.Lock())
             {
                 this.ApplyConvolution(firstPassPixels, sourcePixels, source.Bounds, this.KernelX);
@@ -84,9 +84,11 @@ namespace ImageSharp.Processing.Processors
                 this.ParallelOptions,
                 y =>
                 {
+                    Span<TPixel> targetRow = targetPixels.GetRowSpan(y);
+
                     for (int x = startX; x < endX; x++)
                     {
-                        Vector4 destination = default(Vector4);
+                        var destination = default(Vector4);
 
                         // Apply each matrix multiplier to the color components for each pixel.
                         for (int fy = 0; fy < kernelHeight; fy++)
@@ -95,6 +97,7 @@ namespace ImageSharp.Processing.Processors
                             int offsetY = y + fyr;
 
                             offsetY = offsetY.Clamp(0, maxY);
+                            Span<TPixel> row = sourcePixels.GetRowSpan(offsetY);
 
                             for (int fx = 0; fx < kernelWidth; fx++)
                             {
@@ -103,14 +106,13 @@ namespace ImageSharp.Processing.Processors
 
                                 offsetX = offsetX.Clamp(0, maxX);
 
-                                Vector4 currentColor = sourcePixels[offsetX, offsetY].ToVector4();
+                                var currentColor = row[offsetX].ToVector4();
                                 destination += kernel[fy, fx] * currentColor;
                             }
                         }
 
-                        TPixel packed = default(TPixel);
-                        packed.PackFromVector4(destination);
-                        targetPixels[x, y] = packed;
+                        ref TPixel pixel = ref targetRow[x];
+                        pixel.PackFromVector4(destination);
                     }
                 });
         }

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

@@ -46,10 +46,9 @@ namespace ImageSharp.Processing.Processors
             int maxY = endY - 1;
             int maxX = endX - 1;
 
-            using (PixelAccessor<TPixel> targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
-            using (PixelAccessor<TPixel> sourcePixels = source.Lock())
+            using (var targetPixels = new PixelAccessor<TPixel>(source.Width, source.Height))
             {
-                sourcePixels.CopyTo(targetPixels);
+                source.CopyTo(targetPixels);
 
                 Parallel.For(
                  startY,
@@ -57,6 +56,9 @@ namespace ImageSharp.Processing.Processors
                  this.ParallelOptions,
                  y =>
                  {
+                     Span<TPixel> sourceRow = source.GetRowSpan(y);
+                     Span<TPixel> targetRow = targetPixels.GetRowSpan(y);
+
                      for (int x = startX; x < endX; x++)
                      {
                          float red = 0;
@@ -70,6 +72,7 @@ namespace ImageSharp.Processing.Processors
                              int offsetY = y + fyr;
 
                              offsetY = offsetY.Clamp(0, maxY);
+                             Span<TPixel> sourceOffsetRow = source.GetRowSpan(offsetY);
 
                              for (int fx = 0; fx < kernelLength; fx++)
                              {
@@ -78,7 +81,7 @@ namespace ImageSharp.Processing.Processors
 
                                  offsetX = offsetX.Clamp(0, maxX);
 
-                                 Vector4 currentColor = sourcePixels[offsetX, offsetY].ToVector4();
+                                 var currentColor = sourceOffsetRow[offsetX].ToVector4();
                                  currentColor *= this.KernelXY[fy, fx];
 
                                  red += currentColor.X;
@@ -87,9 +90,8 @@ namespace ImageSharp.Processing.Processors
                              }
                          }
 
-                         TPixel packed = default(TPixel);
-                         packed.PackFromVector4(new Vector4(red, green, blue, sourcePixels[x, y].ToVector4().W));
-                         targetPixels[x, y] = packed;
+                         ref TPixel pixel = ref targetRow[x];
+                         pixel.PackFromVector4(new Vector4(red, green, blue, sourceRow[x].ToVector4().W));
                      }
                  });