improved, sequential ResizeProcessor

src/ImageSharp/Common/Memory/PinnedImageBuffer{T}.cs

@@ -53,7 +53,14 @@ namespace ImageSharp
         /// <param name="x">The x coordinate (row)</param>
         /// <param name="y">The y coordinate (position at row)</param>
         /// <returns>A reference to the element.</returns>
-        public ref T this[int x, int y] => ref this.Array[(this.Width * y) + x];
+        public ref T this[int x, int y]
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+                return ref this.Array[(this.Width * y) + x];
+            }
+        }
 
         /// <summary>
         /// Creates a clean instance of <see cref="PinnedImageBuffer{T}"/> initializing it's elements with 'default(T)'.

src/ImageSharp/Processing/Processors/Transforms/ResamplingWeightedProcessor.Weights.cs

@@ -51,19 +51,22 @@ namespace ImageSharp.Processing.Processors
             /// </summary>
             /// <param name="rowSpan">The input span of vectors</param>
             /// <returns>The weighted sum</returns>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public Vector4 ComputeWeightedRowSum(BufferSpan<Vector4> rowSpan)
             {
                 float* horizontalValues = this.Ptr;
                 int left = this.Left;
+                Vector4* vecPtr = (Vector4*)rowSpan.PointerAtOffset;
+                vecPtr += left;
 
                 // Destination color components
                 Vector4 result = Vector4.Zero;
 
                 for (int i = 0; i < this.Length; i++)
                 {
-                    float xw = horizontalValues[i];
-                    int index = left + i;
-                    result += rowSpan[index] * xw;
+                    float weight = horizontalValues[i];
+                    result += (*vecPtr) * weight;
+                    vecPtr++;
                 }
 
                 return result;
@@ -75,19 +78,22 @@ namespace ImageSharp.Processing.Processors
             /// </summary>
             /// <param name="rowSpan">The input span of vectors</param>
             /// <returns>The weighted sum</returns>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public Vector4 ComputeExpandedWeightedRowSum(BufferSpan<Vector4> rowSpan)
             {
                 float* horizontalValues = this.Ptr;
                 int left = this.Left;
+                Vector4* vecPtr = (Vector4*)rowSpan.PointerAtOffset;
+                vecPtr += left;
 
                 // Destination color components
                 Vector4 result = Vector4.Zero;
 
                 for (int i = 0; i < this.Length; i++)
                 {
-                    float xw = horizontalValues[i];
-                    int index = left + i;
-                    result += rowSpan[index].Expand() * xw;
+                    float weight = horizontalValues[i];
+                    result += (*vecPtr).Expand() * weight;
+                    vecPtr++;
                 }
 
                 return result;
@@ -100,6 +106,7 @@ namespace ImageSharp.Processing.Processors
             /// <param name="firstPassPixels">The buffer of input vectors in row first order</param>
             /// <param name="x">The column position</param>
             /// <returns>The weighted sum</returns>
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
             public Vector4 ComputeWeightedColumnSum(PinnedImageBuffer<Vector4> firstPassPixels, int x)
             {
                 float* verticalValues = this.Ptr;

src/ImageSharp/Processing/Processors/Transforms/ResizeProcessor.cs

@@ -110,76 +110,64 @@ namespace ImageSharp.Processing.Processors
                 {
                     firstPassPixels.Clear();
 
-                    Parallel.For(
-                        0,
-                        sourceRectangle.Bottom,
-                        this.ParallelOptions,
-                        y =>
-                            {
-                                // TODO: Without Parallel.For() this buffer object could be reused:
-                                using (PinnedBuffer<Vector4> tempRowBuffer = new PinnedBuffer<Vector4>(sourcePixels.Width))
-                                {
-                                    BufferSpan<TColor> sourceRow = sourcePixels.GetRowSpan(y);
-
-                                    BulkPixelOperations<TColor>.Instance.ToVector4(
-                                        sourceRow,
-                                        tempRowBuffer,
-                                        sourceRow.Length);
-
-                                    if (this.Compand)
-                                    {
-                                        for (int x = minX; x < maxX; x++)
-                                        {
-                                            WeightsWindow window = this.HorizontalWeights.Weights[x - startX];
-                                            firstPassPixels[x, y] = window.ComputeExpandedWeightedRowSum(tempRowBuffer);
-                                        }
-                                    }
-                                    else
-                                    {
-                                        for (int x = minX; x < maxX; x++)
-                                        {
-                                            WeightsWindow window = this.HorizontalWeights.Weights[x - startX];
-                                            firstPassPixels[x, y] = window.ComputeWeightedRowSum(tempRowBuffer);
-                                        }
-                                    }
-                                }
-                            });
-
-                    // Now process the rows.
-                    Parallel.For(
-                        minY,
-                        maxY,
-                        this.ParallelOptions,
-                        y =>
+                    using (PinnedBuffer<Vector4> tempRowBuffer = new PinnedBuffer<Vector4>(sourcePixels.Width))
+                    {
+                        for (int y = 0; y < sourceRectangle.Bottom; y++)
                         {
-                            // Ensure offsets are normalised for cropping and padding.
-                            WeightsWindow window = this.VerticalWeights.Weights[y - startY];
+                            BufferSpan<TColor> sourceRow = sourcePixels.GetRowSpan(y);
+
+                            BulkPixelOperations<TColor>.Instance.ToVector4(sourceRow, tempRowBuffer, sourceRow.Length);
 
                             if (this.Compand)
                             {
-                                for (int x = 0; x < width; x++)
+                                for (int x = minX; x < maxX; x++)
                                 {
-                                    // Destination color components
-                                    Vector4 destination = window.ComputeWeightedColumnSum(firstPassPixels, x);
-                                    destination = destination.Compress();
-                                    TColor d = default(TColor);
-                                    d.PackFromVector4(destination);
-                                    targetPixels[x, y] = d;
+                                    WeightsWindow window = this.HorizontalWeights.Weights[x - startX];
+                                    firstPassPixels[x, y] = window.ComputeExpandedWeightedRowSum(tempRowBuffer);
                                 }
                             }
                             else
                             {
-                                for (int x = 0; x < width; x++)
+                                for (int x = minX; x < maxX; x++)
                                 {
-                                    // Destination color components
-                                    Vector4 destination = window.ComputeWeightedColumnSum(firstPassPixels, x);
-
-                                    TColor d = default(TColor);
-                                    d.PackFromVector4(destination);
-                                    targetPixels[x, y] = d;
+                                    WeightsWindow window = this.HorizontalWeights.Weights[x - startX];
+                                    firstPassPixels[x, y] = window.ComputeWeightedRowSum(tempRowBuffer);
                                 }
                             }
-                        });
+                        }
+                    }
+
+                    // Now process the rows.
+                    for (int y = minY; y < maxY; y++)
+                    {
+                        // Ensure offsets are normalised for cropping and padding.
+                        WeightsWindow window = this.VerticalWeights.Weights[y - startY];
+
+                        if (this.Compand)
+                        {
+                            for (int x = 0; x < width; x++)
+                            {
+                                // Destination color components
+                                Vector4 destination = window.ComputeWeightedColumnSum(firstPassPixels, x);
+                                destination = destination.Compress();
+                                TColor d = default(TColor);
+                                d.PackFromVector4(destination);
+                                targetPixels[x, y] = d;
+                            }
+                        }
+                        else
+                        {
+                            for (int x = 0; x < width; x++)
+                            {
+                                // Destination color components
+                                Vector4 destination = window.ComputeWeightedColumnSum(firstPassPixels, x);
+
+                                TColor d = default(TColor);
+                                d.PackFromVector4(destination);
+                                targetPixels[x, y] = d;
+                            }
+                        }
+                    }
                 }
 
                 source.SwapPixelsBuffers(targetPixels);

tests/ImageSharp.Sandbox46/Program.cs

@@ -38,12 +38,19 @@ namespace ImageSharp.Sandbox46
         public static void Main(string[] args)
         {
             // RunDecodeJpegProfilingTests();
+            // RunToVector4ProfilingTest();
 
-            RunToVector4ProfilingTest();
+            RunResizeProfilingTest();
 
             Console.ReadLine();
         }
 
+        private static void RunResizeProfilingTest()
+        {
+            ResizeProfilingBenchmarks test = new ResizeProfilingBenchmarks(new ConsoleOutput());
+            test.ResizeBicubic(2000, 2000);
+        }
+
         private static void RunToVector4ProfilingTest()
         {
             BulkPixelOperationsTests.Color tests = new BulkPixelOperationsTests.Color(new ConsoleOutput());

tests/ImageSharp.Tests/Processors/Filters/ResizeTests.cs

@@ -21,7 +21,7 @@ namespace ImageSharp.Tests
 
         [Theory]
         [InlineData(100, 100)]
-        [InlineData(1000, 1000)]
+        [InlineData(2000, 2000)]
         public void ResizeBicubic(int width, int height)
         {
             this.Measure(this.ExecutionCount,