Better performance

src/ImageSharp/Memory/DiscontiguousBuffers/IMemoryGroup{T}.cs

@@ -18,12 +18,12 @@ namespace SixLabors.ImageSharp.Memory
         /// Gets the number of elements per contiguous sub-buffer preceding the last buffer.
         /// The last buffer is allowed to be smaller.
         /// </summary>
-        public int BufferLength { get; }
+        int BufferLength { get; }
 
         /// <summary>
         /// Gets the aggregate number of elements in the group.
         /// </summary>
-        public long TotalLength { get; }
+        long TotalLength { get; }
 
         /// <summary>
         /// Gets a value indicating whether the group has been invalidated.

src/ImageSharp/Processing/Processors/Dithering/ErrorDither.cs

@@ -131,7 +131,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
                 for (int x = bounds.Left; x < bounds.Right; x++)
                 {
                     TPixel sourcePixel = row[x];
-                    TPixel transformed = processor.GetPaletteColor(sourcePixel, palette);
+                    TPixel transformed = Unsafe.AsRef(processor).GetPaletteColor(sourcePixel, palette);
                     this.Dither(source, bounds, sourcePixel, transformed, x, y, scale);
                     row[x] = transformed;
                 }

src/ImageSharp/Processing/Processors/Dithering/IPaletteDitherImageProcessor{TPixel}.cs

@@ -14,9 +14,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
         where TPixel : unmanaged, IPixel<TPixel>
     {
         /// <summary>
-        /// Gets the configration instance to use when performing operations.
+        /// Gets the configuration instance to use when performing operations.
         /// </summary>
-        public Configuration Configuration { get; }
+        Configuration Configuration { get; }
 
         /// <summary>
         /// Gets the dithering palette.

src/ImageSharp/Processing/Processors/Dithering/OrderedDither.KnownTypes.cs

@@ -6,7 +6,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
     /// <content>
     /// An ordered dithering matrix with equal sides of arbitrary length
     /// </content>
-    public readonly partial struct OrderedDither : IDither
+    public readonly partial struct OrderedDither
     {
         /// <summary>
         /// Applies order dithering using the 2x2 Bayer dithering matrix.

src/ImageSharp/Processing/Processors/Dithering/OrderedDither.cs

@@ -237,7 +237,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
                     for (int x = this.bounds.Left; x < this.bounds.Right; x++)
                     {
                         TPixel dithered = this.dither.Dither(sourceRow[x], x, y, this.bitDepth, scale);
-                        destinationRow[x - offsetX] = this.quantizer.GetQuantizedColor(dithered, paletteSpan, out TPixel _);
+                        destinationRow[x - offsetX] = Unsafe.AsRef(this.quantizer).GetQuantizedColor(dithered, paletteSpan, out TPixel _);
                     }
                 }
             }
@@ -281,7 +281,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
                     {
                         ref TPixel sourcePixel = ref row[x];
                         TPixel dithered = this.dither.Dither(sourcePixel, x, y, this.bitDepth, this.scale);
-                        sourcePixel = this.processor.GetPaletteColor(dithered, paletteSpan);
+                        sourcePixel = Unsafe.AsRef(this.processor).GetPaletteColor(dithered, paletteSpan);
                     }
                 }
             }

src/ImageSharp/Processing/Processors/Dithering/PaletteDitherProcessor{TPixel}.cs

@@ -84,7 +84,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Dithering
                 float ditherScale)
             {
                 this.Configuration = configuration;
-                this.pixelMap = new EuclideanPixelMap<TPixel>(palette);
+                this.pixelMap = new EuclideanPixelMap<TPixel>(configuration, palette);
                 this.Palette = palette;
                 this.DitherScale = ditherScale;
             }

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

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Concurrent;
 using System.Numerics;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Quantization
@@ -17,27 +18,25 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     internal readonly struct EuclideanPixelMap<TPixel> : IPixelMap<TPixel>, IEquatable<EuclideanPixelMap<TPixel>>
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        private readonly ConcurrentDictionary<int, Vector4> vectorCache;
+        private readonly Vector4[] vectorCache;
         private readonly ConcurrentDictionary<TPixel, int> distanceCache;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="EuclideanPixelMap{TPixel}"/> struct.
         /// </summary>
+        /// <param name="configuration">The configuration.</param>
         /// <param name="palette">The color palette to map from.</param>
         [MethodImpl(InliningOptions.ShortMethod)]
-        public EuclideanPixelMap(ReadOnlyMemory<TPixel> palette)
+        public EuclideanPixelMap(Configuration configuration, ReadOnlyMemory<TPixel> palette)
         {
             Guard.MustBeGreaterThan(palette.Length, 0, nameof(palette));
 
             this.Palette = palette;
             ReadOnlySpan<TPixel> paletteSpan = this.Palette.Span;
-            this.vectorCache = new ConcurrentDictionary<int, Vector4>();
+            this.vectorCache = new Vector4[paletteSpan.Length];
             this.distanceCache = new ConcurrentDictionary<TPixel, int>();
 
-            for (int i = 0; i < paletteSpan.Length; i++)
-            {
-                this.vectorCache[i] = paletteSpan[i].ToScaledVector4();
-            }
+            PixelOperations<TPixel>.Instance.ToVector4(configuration, paletteSpan, this.vectorCache);
         }
 
         /// <inheritdoc/>
@@ -81,31 +80,32 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             int index = 0;
             float leastDistance = float.MaxValue;
             Vector4 vector = color.ToScaledVector4();
+            ref TPixel paletteRef = ref MemoryMarshal.GetReference(palette);
+            ref Vector4 vectorCacheRef = ref MemoryMarshal.GetReference<Vector4>(this.vectorCache);
 
             for (int i = 0; i < palette.Length; i++)
             {
-                Vector4 candidate = this.vectorCache[i];
+                Vector4 candidate = Unsafe.Add(ref vectorCacheRef, i);
                 float distance = Vector4.DistanceSquared(vector, candidate);
 
-                if (!(distance < leastDistance))
+                // If it's an exact match, exit the loop
+                if (distance == 0)
                 {
-                    continue;
+                    index = i;
+                    break;
                 }
 
-                // Less than... assign.
-                index = i;
-                leastDistance = distance;
-
-                // And if it's an exact match, exit the loop
-                if (distance == 0)
+                if (distance < leastDistance)
                 {
-                    break;
+                    // Less than... assign.
+                    index = i;
+                    leastDistance = distance;
                 }
             }
 
             // Now I have the index, pop it into the cache for next time
             this.distanceCache[color] = index;
-            match = palette[index];
+            match = Unsafe.Add(ref paletteRef, index);
             return index;
         }
     }

src/ImageSharp/Processing/Processors/Quantization/FrameQuantizerExtensions.cs

@@ -117,7 +117,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
 
                     for (int x = this.bounds.Left; x < this.bounds.Right; x++)
                     {
-                        destinationRow[x - offsetX] = this.quantizer.GetQuantizedColor(sourceRow[x], paletteSpan, out TPixel _);
+                        destinationRow[x - offsetX] = Unsafe.AsRef(this.quantizer).GetQuantizedColor(sourceRow[x], paletteSpan, out TPixel _);
                     }
                 }
             }

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

@@ -85,7 +85,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             this.octree.Palletize(paletteSpan, this.colors);
 
             // TODO: Cannot make method readonly due to this line.
-            this.pixelMap = new EuclideanPixelMap<TPixel>(this.palette.Memory);
+            this.pixelMap = new EuclideanPixelMap<TPixel>(this.Configuration, this.palette.Memory);
 
             return paletteSpan;
         }

src/ImageSharp/Processing/Processors/Quantization/OctreeQuantizer.cs

@@ -11,12 +11,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class OctreeQuantizer : IQuantizer
     {
+        private static readonly QuantizerOptions DefaultOptions = new QuantizerOptions();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="OctreeQuantizer"/> class
         /// using the default <see cref="QuantizerOptions"/>.
         /// </summary>
         public OctreeQuantizer()
-            : this(new QuantizerOptions())
+            : this(DefaultOptions)
         {
         }
 

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

@@ -40,7 +40,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             this.paletteOwner = configuration.MemoryAllocator.Allocate<TPixel>(maxLength);
             Color.ToPixel(configuration, colors, this.paletteOwner.GetSpan());
 
-            this.pixelMap = new EuclideanPixelMap<TPixel>(this.paletteOwner.Memory);
+            this.pixelMap = new EuclideanPixelMap<TPixel>(configuration, this.paletteOwner.Memory);
             this.isDisposed = false;
         }
 
@@ -63,7 +63,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             this.paletteOwner = configuration.MemoryAllocator.Allocate<TPixel>(maxLength);
             palette.CopyTo(this.paletteOwner.GetSpan());
 
-            this.pixelMap = new EuclideanPixelMap<TPixel>(this.paletteOwner.Memory);
+            this.pixelMap = new EuclideanPixelMap<TPixel>(configuration, this.paletteOwner.Memory);
             this.isDisposed = false;
         }
 

src/ImageSharp/Processing/Processors/Quantization/PaletteQuantizer.cs

@@ -11,6 +11,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class PaletteQuantizer : IQuantizer
     {
+        private static readonly QuantizerOptions DefaultOptions = new QuantizerOptions();
         private readonly ReadOnlyMemory<Color> palette;
 
         /// <summary>
@@ -18,7 +19,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// </summary>
         /// <param name="palette">The color palette.</param>
         public PaletteQuantizer(ReadOnlyMemory<Color> palette)
-            : this(palette, new QuantizerOptions())
+            : this(palette, DefaultOptions)
         {
         }
 

src/ImageSharp/Processing/Processors/Quantization/WebSafePaletteQuantizer.cs

@@ -10,11 +10,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class WebSafePaletteQuantizer : PaletteQuantizer
     {
+        private static readonly QuantizerOptions DefaultOptions = new QuantizerOptions();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="WebSafePaletteQuantizer" /> class.
         /// </summary>
         public WebSafePaletteQuantizer()
-            : this(new QuantizerOptions())
+            : this(DefaultOptions)
         {
         }
 

src/ImageSharp/Processing/Processors/Quantization/WernerPaletteQuantizer.cs

@@ -9,11 +9,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class WernerPaletteQuantizer : PaletteQuantizer
     {
+        private static readonly QuantizerOptions DefaultOptions = new QuantizerOptions();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="WernerPaletteQuantizer" /> class.
         /// </summary>
         public WernerPaletteQuantizer()
-            : this(new QuantizerOptions())
+            : this(DefaultOptions)
         {
         }
 

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

@@ -132,30 +132,30 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             }
 
             // TODO: Cannot make methods readonly due to this line.
-            this.pixelMap = new EuclideanPixelMap<TPixel>(this.palette.Memory);
+            this.pixelMap = new EuclideanPixelMap<TPixel>(this.Configuration, this.palette.Memory);
             return paletteSpan;
         }
 
         /// <inheritdoc/>
         public readonly byte GetQuantizedColor(TPixel color, ReadOnlySpan<TPixel> palette, out TPixel match)
         {
-            if (!this.isDithering)
+            if (this.isDithering)
             {
-                Rgba32 rgba = default;
-                color.ToRgba32(ref rgba);
-
-                int r = rgba.R >> (8 - IndexBits);
-                int g = rgba.G >> (8 - IndexBits);
-                int b = rgba.B >> (8 - IndexBits);
-                int a = rgba.A >> (8 - IndexAlphaBits);
-
-                ReadOnlySpan<byte> tagSpan = this.tag.GetSpan();
-                byte index = tagSpan[GetPaletteIndex(r + 1, g + 1, b + 1, a + 1)];
-                match = palette[index];
-                return index;
+                return (byte)this.pixelMap.GetClosestColor(color, out match);
             }
 
-            return (byte)this.pixelMap.GetClosestColor(color, out match);
+            Rgba32 rgba = default;
+            color.ToRgba32(ref rgba);
+
+            int r = rgba.R >> (8 - IndexBits);
+            int g = rgba.G >> (8 - IndexBits);
+            int b = rgba.B >> (8 - IndexBits);
+            int a = rgba.A >> (8 - IndexAlphaBits);
+
+            ReadOnlySpan<byte> tagSpan = this.tag.GetSpan();
+            byte index = tagSpan[GetPaletteIndex(r + 1, g + 1, b + 1, a + 1)];
+            match = palette[index];
+            return index;
         }
 
         /// <inheritdoc/>
@@ -376,11 +376,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <summary>
         /// Converts the histogram into moments so that we can rapidly calculate the sums of the above quantities over any desired box.
         /// </summary>
-        /// <param name="memoryAllocator">The memory allocator used for allocating buffers.</param>
-        private void Get3DMoments(MemoryAllocator memoryAllocator)
+        /// <param name="allocator">The memory allocator used for allocating buffers.</param>
+        private void Get3DMoments(MemoryAllocator allocator)
         {
-            using IMemoryOwner<Moment> volume = memoryAllocator.Allocate<Moment>(IndexCount * IndexAlphaCount);
-            using IMemoryOwner<Moment> area = memoryAllocator.Allocate<Moment>(IndexAlphaCount);
+            using IMemoryOwner<Moment> volume = allocator.Allocate<Moment>(IndexCount * IndexAlphaCount);
+            using IMemoryOwner<Moment> area = allocator.Allocate<Moment>(IndexAlphaCount);
 
             Span<Moment> momentSpan = this.moments.GetSpan();
             Span<Moment> volumeSpan = volume.GetSpan();

src/ImageSharp/Processing/Processors/Quantization/WuQuantizer.cs

@@ -10,12 +10,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
     /// </summary>
     public class WuQuantizer : IQuantizer
     {
+        private static readonly QuantizerOptions DefaultOptions = new QuantizerOptions();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="WuQuantizer"/> class
         /// using the default <see cref="QuantizerOptions"/>.
         /// </summary>
         public WuQuantizer()
-            : this(new QuantizerOptions())
+            : this(DefaultOptions)
         {
         }