bitwise conversion + benchmarks WIP

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegImagePostProcessor.cs

@@ -162,7 +162,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                 this.colorConverter.ConvertToRgba(values, this.rgbaBuffer.GetSpan());
 
                 Span<TPixel> destRow = destination.GetPixelRowSpan(yy);
-                
+
                 // TODO: Investigate if slicing is actually necessary
                 PixelOperations<TPixel>.Instance.FromVector4(this.configuration, this.rgbaBuffer.GetSpan().Slice(0, destRow.Length), destRow);
             }

src/ImageSharp/PixelFormats/PixelConverter.cs

@@ -0,0 +1,47 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp.PixelFormats
+{
+    /// <summary>
+    /// Contains optimized implementations for conversion between pixel formats.
+    /// </summary>
+    /// <remarks>
+    /// Implementations are based on ideas in:
+    /// https://github.com/dotnet/coreclr/blob/master/src/System.Private.CoreLib/shared/System/Buffers/Binary/Reader.cs#L84
+    /// The JIT should be able to detect and optimize ROL and ROR patterns.
+    /// </remarks>
+    internal static class PixelConverter
+    {
+        public static class Rgba32
+        {
+            /// <summary>
+            /// Converts a packed <see cref="PixelFormats.Rgba32"/> to <see cref="Argb32"/>.
+            /// </summary>
+            [MethodImpl(InliningOptions.ShortMethod)]
+            public static uint ToArgb32(uint packedRgba)
+            {
+                // packedRgba = [aa bb gg rr]
+                // ROL(8, packedRgba):
+                return (packedRgba << 8) | (packedRgba >> 24);
+            }
+        }
+
+        public static class Argb32
+        {
+            /// <summary>
+            /// Converts a packed <see cref="Argb32"/> to <see cref="PixelFormats.Rgba32"/>.
+            /// </summary>
+            [MethodImpl(InliningOptions.ShortMethod)]
+            public static uint ToRgba32(uint packedArgb)
+            {
+                // packedArgb = [bb gg rr aa]
+                // ROR(8, packedArgb):
+                return (packedArgb >> 8) | (packedArgb << 24);
+            }
+        }
+    }
+}

src/ImageSharp/Processing/Processors/Quantization/FrameQuantizerBase{TPixel}.cs

@@ -17,8 +17,6 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     public abstract class FrameQuantizerBase<TPixel> : IFrameQuantizer<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
-        private readonly Configuration configuration;
-
         /// <summary>
         /// A lookup table for colors
         /// </summary>

tests/ImageSharp.Benchmarks/General/PixelConversion/PixelConversion_ConvertFromRgba32.cs

@@ -1,6 +1,8 @@
 // ReSharper disable InconsistentNaming
 
+using System;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 using BenchmarkDotNet.Attributes;
 
@@ -8,14 +10,14 @@ using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
 {
-    public class PixelConversion_ConvertFromRgba32
+    public abstract class PixelConversion_ConvertFromRgba32
     {
-        struct ConversionRunner<T>
+        internal struct ConversionRunner<T>
             where T : struct, ITestPixel<T>
         {
-            private T[] dest;
+            public readonly T[] dest;
 
-            private Rgba32[] source;
+            public readonly Rgba32[] source;
 
             public ConversionRunner(int count)
             {
@@ -67,72 +69,146 @@ namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
             }
         }
         
-        private ConversionRunner<TestRgba> compatibleMemLayoutRunner;
+        internal ConversionRunner<TestRgba> compatibleMemLayoutRunner;
 
-        private ConversionRunner<TestArgb> permutedRunner;
+        internal ConversionRunner<TestArgb> permutedRunnerRgbaToArgb;
 
-        [Params(32)]
+        [Params(
+            256,
+            2048
+        )]
         public int Count { get; set; }
 
         [GlobalSetup]
         public void Setup()
         {
             this.compatibleMemLayoutRunner = new ConversionRunner<TestRgba>(this.Count);
-            this.permutedRunner = new ConversionRunner<TestArgb>(this.Count);
+            this.permutedRunnerRgbaToArgb = new ConversionRunner<TestArgb>(this.Count);
         }
+    }
 
+    public class PixelConversion_ConvertFromRgba32_Compatible : PixelConversion_ConvertFromRgba32
+    {
         [Benchmark(Baseline = true)]
-        public void CompatibleByRef()
+        public void ByRef()
         {
             this.compatibleMemLayoutRunner.RunByRefConversion();
         }
 
         [Benchmark]
-        public void CompatibleByVal()
+        public void ByVal()
         {
             this.compatibleMemLayoutRunner.RunByValConversion();
         }
 
         [Benchmark]
-        public void CompatibleFromBytes()
+        public void FromBytes()
         {
             this.compatibleMemLayoutRunner.RunFromBytesConversion();
         }
 
+        [Benchmark]
+        public void Inline()
+        {
+            ref Rgba32 sBase = ref this.compatibleMemLayoutRunner.source[0];
+            ref Rgba32 dBase = ref Unsafe.As<TestRgba, Rgba32>(ref this.compatibleMemLayoutRunner.dest[0]);
+
+            for (int i = 0; i < this.Count; i++)
+            {
+                Unsafe.Add(ref dBase, i) = Unsafe.Add(ref sBase, i);
+            }
+        }
+
+        //     Method | Count |     Mean |    Error |   StdDev | Scaled | ScaledSD |
+        // ---------- |------ |---------:|---------:|---------:|-------:|---------:|
+        //      ByRef |   256 | 128.5 ns | 1.217 ns | 1.138 ns |   1.00 |     0.00 |
+        //      ByVal |   256 | 196.7 ns | 2.792 ns | 2.612 ns |   1.53 |     0.02 |
+        //  FromBytes |   256 | 321.7 ns | 2.180 ns | 1.820 ns |   2.50 |     0.03 |
+        //     Inline |   256 | 129.9 ns | 2.759 ns | 2.581 ns |   1.01 |     0.02 |
+    }
+
+    public class PixelConversion_ConvertFromRgba32_Permuted_RgbaToArgb : PixelConversion_ConvertFromRgba32
+    {
+        [Benchmark(Baseline = true)]
+        public void ByRef()
+        {
+            this.permutedRunnerRgbaToArgb.RunByRefConversion();
+        }
+
+        [Benchmark]
+        public void ByVal()
+        {
+            this.permutedRunnerRgbaToArgb.RunByValConversion();
+        }
+
+        [Benchmark]
+        public void FromBytes()
+        {
+            this.permutedRunnerRgbaToArgb.RunFromBytesConversion();
+        }
 
         [Benchmark]
-        public void PermutedByRef()
+        public void InlineShuffle()
         {
-            this.permutedRunner.RunByRefConversion();
+            ref Rgba32 sBase = ref this.permutedRunnerRgbaToArgb.source[0];
+            ref TestArgb dBase = ref this.permutedRunnerRgbaToArgb.dest[0];
+
+            for (int i = 0; i < this.Count; i++)
+            {
+                Rgba32 s = Unsafe.Add(ref sBase, i);
+                ref TestArgb d = ref Unsafe.Add(ref dBase, i);
+
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+            }
         }
 
         [Benchmark]
-        public void PermutedByVal()
+        public void PixelConverter_Rgba32_ToArgb32()
         {
-            this.permutedRunner.RunByValConversion();
+            ref uint sBase = ref Unsafe.As<Rgba32, uint>(ref this.permutedRunnerRgbaToArgb.source[0]);
+            ref uint dBase = ref Unsafe.As<TestArgb, uint>(ref this.permutedRunnerRgbaToArgb.dest[0]);
+
+            for (int i = 0; i < this.Count; i++)
+            {
+                uint s = Unsafe.Add(ref sBase, i);
+                Unsafe.Add(ref dBase, i) = PixelConverter.Rgba32.ToArgb32(s);
+            }
         }
 
         [Benchmark]
-        public void PermutedFromBytes()
+        public void PixelConverter_Rgba32_ToArgb32_CopyThenWorkOnSingleBuffer()
         {
-            this.permutedRunner.RunFromBytesConversion();
+            Span<uint> source = MemoryMarshal.Cast<Rgba32, uint>(this.permutedRunnerRgbaToArgb.source);
+            Span<uint> dest = MemoryMarshal.Cast<TestArgb, uint>(this.permutedRunnerRgbaToArgb.dest);
+            source.CopyTo(dest);
+
+            ref uint dBase = ref MemoryMarshal.GetReference(dest);
+
+            for (int i = 0; i < this.Count; i++)
+            {
+                uint s = Unsafe.Add(ref dBase, i);
+                Unsafe.Add(ref dBase, i) = PixelConverter.Rgba32.ToArgb32(s);
+            }
         }
-    }
 
-    /*
-     * Results:
-     *              Method | Count |       Mean |    StdDev | Scaled | Scaled-StdDev |
-     *  ------------------ |------ |----------- |---------- |------- |-------------- |
-     *     CompatibleByRef |    32 | 20.6339 ns | 0.0742 ns |   1.00 |          0.00 |
-     *     CompatibleByVal |    32 | 23.7425 ns | 0.0997 ns |   1.15 |          0.01 |
-     * CompatibleFromBytes |    32 | 38.7017 ns | 0.1103 ns |   1.88 |          0.01 |
-     *       PermutedByRef |    32 | 39.2892 ns | 0.1366 ns |   1.90 |          0.01 |
-     *       PermutedByVal |    32 | 38.5178 ns | 0.1946 ns |   1.87 |          0.01 |
-     *   PermutedFromBytes |    32 | 38.6683 ns | 0.0801 ns |   1.87 |          0.01 |
-     *  
-     *  !!! Conclusion !!!
-     *  All memory-incompatible (permuted) variants are equivalent with the the "FromBytes" solution. 
-     *  In memory compatible cases we should use the optimized Bulk-copying variant anyways, 
-     *  so there is no benefit introducing non-bulk API-s other than FromBytes() OR FromRgba32().
-     */
+        // RESULTS:
+        //                                                     Method | Count |       Mean |      Error |     StdDev | Scaled | ScaledSD |
+        // ---------------------------------------------------------- |------ |-----------:|-----------:|-----------:|-------:|---------:|
+        //                                                      ByRef |   256 |   328.7 ns |  6.6141 ns |  6.1868 ns |   1.00 |     0.00 |
+        //                                                      ByVal |   256 |   322.0 ns |  4.3541 ns |  4.0728 ns |   0.98 |     0.02 |
+        //                                                  FromBytes |   256 |   321.5 ns |  3.3499 ns |  3.1335 ns |   0.98 |     0.02 |
+        //                                              InlineShuffle |   256 |   330.7 ns |  4.2525 ns |  3.9778 ns |   1.01 |     0.02 |
+        //                             PixelConverter_Rgba32_ToArgb32 |   256 |   167.4 ns |  0.6357 ns |  0.5309 ns |   0.51 |     0.01 |
+        //  PixelConverter_Rgba32_ToArgb32_CopyThenWorkOnSingleBuffer |   256 |   196.6 ns |  0.8929 ns |  0.7915 ns |   0.60 |     0.01 |
+        //                                                            |       |            |            |            |        |          |
+        //                                                      ByRef |  2048 | 2,534.4 ns |  8.2947 ns |  6.9265 ns |   1.00 |     0.00 |
+        //                                                      ByVal |  2048 | 2,638.5 ns | 52.6843 ns | 70.3320 ns |   1.04 |     0.03 |
+        //                                                  FromBytes |  2048 | 2,517.2 ns | 40.8055 ns | 38.1695 ns |   0.99 |     0.01 |
+        //                                              InlineShuffle |  2048 | 2,546.5 ns | 21.2506 ns | 19.8778 ns |   1.00 |     0.01 |
+        //                             PixelConverter_Rgba32_ToArgb32 |  2048 | 1,265.7 ns |  5.1397 ns |  4.5562 ns |   0.50 |     0.00 |
+        //  PixelConverter_Rgba32_ToArgb32_CopyThenWorkOnSingleBuffer |  2048 | 1,410.3 ns | 11.1939 ns |  9.9231 ns |   0.56 |     0.00 |// 
+    }
 }

tests/ImageSharp.Benchmarks/General/PixelConversion/TestArgb.cs

@@ -9,81 +9,81 @@ namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
     [StructLayout(LayoutKind.Sequential)]
     struct TestArgb : ITestPixel<TestArgb>
     {
-        private byte a, r, g, b;
+        public byte A, R, G, B;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromRgba32(Rgba32 p)
         {
-            this.r = p.R;
-            this.g = p.G;
-            this.b = p.B;
-            this.a = p.A;
+            this.R = p.R;
+            this.G = p.G;
+            this.B = p.B;
+            this.A = p.A;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromRgba32(ref Rgba32 p)
         {
-            this.r = p.R;
-            this.g = p.G;
-            this.b = p.B;
-            this.a = p.A;
+            this.R = p.R;
+            this.G = p.G;
+            this.B = p.B;
+            this.A = p.A;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromBytes(byte r, byte g, byte b, byte a)
         {
-            this.r = r;
-            this.g = g;
-            this.b = b;
-            this.a = a;
+            this.R = r;
+            this.G = g;
+            this.B = b;
+            this.A = a;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromVector4(Vector4 p)
         {
-            this.r = (byte)p.X;
-            this.g = (byte)p.Y;
-            this.b = (byte)p.Z;
-            this.a = (byte)p.W;
+            this.R = (byte)p.X;
+            this.G = (byte)p.Y;
+            this.B = (byte)p.Z;
+            this.A = (byte)p.W;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromVector4(ref Vector4 p)
         {
-            this.r = (byte)p.X;
-            this.g = (byte)p.Y;
-            this.b = (byte)p.Z;
-            this.a = (byte)p.W;
+            this.R = (byte)p.X;
+            this.G = (byte)p.Y;
+            this.B = (byte)p.Z;
+            this.A = (byte)p.W;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public Rgba32 ToRgba32()
         {
-            return new Rgba32(this.r, this.g, this.b, this.a);
+            return new Rgba32(this.R, this.G, this.B, this.A);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void CopyToRgba32(ref Rgba32 dest)
         {
-            dest.R = this.r;
-            dest.G = this.g;
-            dest.B = this.b;
-            dest.A = this.a;
+            dest.R = this.R;
+            dest.G = this.G;
+            dest.B = this.B;
+            dest.A = this.A;
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public Vector4 ToVector4()
         {
-            return new Vector4(this.r, this.g, this.b, this.a);
+            return new Vector4(this.R, this.G, this.B, this.A);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void CopyToVector4(ref Vector4 dest)
         {
-            dest.X = this.r;
-            dest.Y = this.g;
-            dest.Z = this.b;
-            dest.W = this.a;
+            dest.X = this.R;
+            dest.Y = this.G;
+            dest.Z = this.B;
+            dest.W = this.A;
         }
     }
 }

tests/ImageSharp.Benchmarks/General/PixelConversion/TestRgba.cs

@@ -9,7 +9,7 @@ namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
     [StructLayout(LayoutKind.Sequential)]
     struct TestRgba : ITestPixel<TestRgba>
     {
-        private byte r, g, b, a;
+        public byte R, G, B, A;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromRgba32(Rgba32 source)
@@ -26,10 +26,10 @@ namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void FromBytes(byte r, byte g, byte b, byte a)
         {
-            this.r = r;
-            this.g = g;
-            this.b = b;
-            this.a = a;
+            this.R = r;
+            this.G = g;
+            this.B = b;
+            this.A = a;
         }
 
         public void FromVector4(Vector4 source)
@@ -57,13 +57,13 @@ namespace SixLabors.ImageSharp.Benchmarks.General.PixelConversion
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public Vector4 ToVector4()
         {
-            return new Vector4(this.r, this.g, this.b, this.a) *  new Vector4(1f / 255f);
+            return new Vector4(this.R, this.G, this.B, this.A) *  new Vector4(1f / 255f);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void CopyToVector4(ref Vector4 dest)
         {
-            var tmp = new Vector4(this.r, this.g, this.b, this.a);
+            var tmp = new Vector4(this.R, this.G, this.B, this.A);
             tmp *= new Vector4(1f / 255f);
             dest = tmp;
         }

tests/ImageSharp.Tests/PixelFormats/PixelConverterTests.cs

@@ -0,0 +1,150 @@
+using SixLabors.ImageSharp.PixelFormats;
+
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests.PixelFormats
+{
+    public class PixelConverterTests
+    {
+        public static readonly TheoryData<byte, byte, byte, byte> RgbaData =
+            new TheoryData<byte, byte, byte, byte>
+                {
+                    { 0, 0, 0, 0 },
+                    { 0, 0, 0, 255 },
+                    { 0, 0, 255, 0 },
+                    { 0, 255, 0, 0 },
+                    { 255, 0, 0, 0 },
+                    { 255, 255, 255, 255 },
+                    { 0, 0, 0, 1 },
+                    { 0, 0, 1, 0 },
+                    { 0, 1, 0, 0 },
+                    { 1, 0, 0, 0 },
+                    { 3, 5, 7, 11 },
+                    { 67, 71, 101, 109 }
+                };
+
+        [Theory]
+        [MemberData(nameof(RgbaData))]
+        public void Rgba32ToArgb32(byte r, byte g, byte b, byte a)
+        {
+            Rgba32 s = ReferenceImplementations.MakeRgba32(r, g, b, a);
+
+            // Act:
+            uint actualPacked = PixelConverter.Rgba32.ToArgb32(s.PackedValue);
+
+            // Assert:
+            uint expectedPacked = ReferenceImplementations.ToArgb32(s).PackedValue;
+
+            Assert.Equal(expectedPacked, actualPacked);
+        }
+
+        [Theory]
+        [MemberData(nameof(RgbaData))]
+        public void Argb32ToRgba32(byte r, byte g, byte b, byte a)
+        {
+            Argb32 s = ReferenceImplementations.MakeArgb32(r, g, b, a);
+
+            // Act:
+            uint actualPacked = PixelConverter.Argb32.ToRgba32(s.PackedValue);
+
+            // Assert:
+            uint expectedPacked = ReferenceImplementations.ToRgba32(s).PackedValue;
+
+            Assert.Equal(expectedPacked, actualPacked);
+        }
+
+
+        private static class ReferenceImplementations
+        {
+            public static Rgba32 MakeRgba32(byte r, byte g, byte b, byte a)
+            {
+                Rgba32 d = default;
+                d.R = r;
+                d.G = g;
+                d.B = b;
+                d.A = a;
+                return d;
+            }
+
+            public static Argb32 MakeArgb32(byte r, byte g, byte b, byte a)
+            {
+                Argb32 d = default;
+                d.R = r;
+                d.G = g;
+                d.B = b;
+                d.A = a;
+                return d;
+            }
+
+            public static Bgra32 MakeBgra32(byte r, byte g, byte b, byte a)
+            {
+                Bgra32 d = default;
+                d.R = r;
+                d.G = g;
+                d.B = b;
+                d.A = a;
+                return d;
+            }
+
+            public static Argb32 ToArgb32(Rgba32 s)
+            {
+                Argb32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+
+            public static Argb32 ToArgb32(Bgra32 s)
+            {
+                Argb32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+
+            public static Rgba32 ToRgba32(Argb32 s)
+            {
+                Rgba32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+
+            public static Rgba32 ToRgba32(Bgra32 s)
+            {
+                Rgba32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+
+            public static Bgra32 ToBgra32(Rgba32 s)
+            {
+                Bgra32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+
+            public static Bgra32 ToBgra32(Argb32 s)
+            {
+                Bgra32 d = default;
+                d.R = s.R;
+                d.G = s.G;
+                d.B = s.B;
+                d.A = s.A;
+                return d;
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/PixelFormats/Rgba32Tests.cs

@@ -5,6 +5,7 @@ using System;
 using System.Numerics;
 using SixLabors.ImageSharp.PixelFormats;
 using Xunit;
+using Xunit.Abstractions;
 
 namespace SixLabors.ImageSharp.Tests.PixelFormats
 {