Move kernels to reusable struct

src/ImageSharp/ImageSharp.csproj

@@ -20,7 +20,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.SourceLink.GitHub"/>
+    <PackageReference Include="Microsoft.SourceLink.GitHub" />
     <PackageReference Include="MinVer" PrivateAssets="All" />
   </ItemGroup>
   

src/ImageSharp/Processing/EdgeDetectionOperators.cs

@@ -1,61 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Apache License, Version 2.0.
-
-namespace SixLabors.ImageSharp.Processing
-{
-    /// <summary>
-    /// Enumerates the various types of defined edge detection filters.
-    /// </summary>
-    public enum EdgeDetectionOperators
-    {
-        /// <summary>
-        /// The Kayyali operator filter.
-        /// </summary>
-        Kayyali,
-
-        /// <summary>
-        /// The Kirsch operator filter.
-        /// </summary>
-        Kirsch,
-
-        /// <summary>
-        /// The Laplacian3X3 operator filter.
-        /// </summary>
-        Laplacian3x3,
-
-        /// <summary>
-        /// The Laplacian5X5 operator filter.
-        /// </summary>
-        Laplacian5x5,
-
-        /// <summary>
-        /// The LaplacianOfGaussian operator filter.
-        /// </summary>
-        LaplacianOfGaussian,
-
-        /// <summary>
-        /// The Prewitt operator filter.
-        /// </summary>
-        Prewitt,
-
-        /// <summary>
-        /// The RobertsCross operator filter.
-        /// </summary>
-        RobertsCross,
-
-        /// <summary>
-        /// The Robinson operator filter.
-        /// </summary>
-        Robinson,
-
-        /// <summary>
-        /// The Scharr operator filter.
-        /// </summary>
-        Scharr,
-
-        /// <summary>
-        /// The Sobel operator filter.
-        /// </summary>
-        Sobel
-    }
-}

src/ImageSharp/Processing/Extensions/Convolution/DetectEdgesExtensions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 using SixLabors.ImageSharp.Processing.Processors;
@@ -40,7 +40,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
         public static IImageProcessingContext DetectEdges(
             this IImageProcessingContext source,
-            EdgeDetectionOperators filter) =>
+            KnownEdgeDetectionOperators filter) =>
             DetectEdges(source, GetProcessor(filter, true));
 
         /// <summary>
@@ -52,7 +52,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
         public static IImageProcessingContext DetectEdges(
             this IImageProcessingContext source,
-            EdgeDetectionOperators filter,
+            KnownEdgeDetectionOperators filter,
             bool grayscale) =>
             DetectEdges(source, GetProcessor(filter, grayscale));
 
@@ -68,7 +68,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
         public static IImageProcessingContext DetectEdges(
             this IImageProcessingContext source,
-            EdgeDetectionOperators filter,
+            KnownEdgeDetectionOperators filter,
             Rectangle rectangle,
             bool grayscale = true) =>
             DetectEdges(source, rectangle, GetProcessor(filter, grayscale));
@@ -102,45 +102,45 @@ namespace SixLabors.ImageSharp.Processing
             return source;
         }
 
-        private static IImageProcessor GetProcessor(EdgeDetectionOperators filter, bool grayscale)
+        private static IImageProcessor GetProcessor(KnownEdgeDetectionOperators filter, bool grayscale)
         {
             IImageProcessor processor;
 
             switch (filter)
             {
-                case EdgeDetectionOperators.Kayyali:
+                case KnownEdgeDetectionOperators.Kayyali:
                     processor = new KayyaliProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Kirsch:
+                case KnownEdgeDetectionOperators.Kirsch:
                     processor = new KirschProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Laplacian3x3:
+                case KnownEdgeDetectionOperators.Laplacian3x3:
                     processor = new Laplacian3x3Processor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Laplacian5x5:
+                case KnownEdgeDetectionOperators.Laplacian5x5:
                     processor = new Laplacian5x5Processor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.LaplacianOfGaussian:
+                case KnownEdgeDetectionOperators.LaplacianOfGaussian:
                     processor = new LaplacianOfGaussianProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Prewitt:
+                case KnownEdgeDetectionOperators.Prewitt:
                     processor = new PrewittProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.RobertsCross:
+                case KnownEdgeDetectionOperators.RobertsCross:
                     processor = new RobertsCrossProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Robinson:
+                case KnownEdgeDetectionOperators.Robinson:
                     processor = new RobinsonProcessor(grayscale);
                     break;
 
-                case EdgeDetectionOperators.Scharr:
+                case KnownEdgeDetectionOperators.Scharr:
                     processor = new ScharrProcessor(grayscale);
                     break;
 
@@ -152,4 +152,4 @@ namespace SixLabors.ImageSharp.Processing
             return processor;
         }
     }
-}
+}

src/ImageSharp/Processing/KnownEdgeDetectionOperators.cs

@@ -0,0 +1,63 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.Processing.Processors.Convolution;
+
+namespace SixLabors.ImageSharp.Processing
+{
+    /// <summary>
+    /// Contains reusable static instances of known edge detection kernels.
+    /// </summary>
+    public static class KnownEdgeDetectionOperators
+    {
+        /// <summary>
+        /// Gets the Kayyali edge detector kernel.
+        /// </summary>
+        public static EdgeDetector2DKernel Kayyali { get; } = EdgeDetector2DKernel.KayyaliKernel;
+
+        /// <summary>
+        /// Gets the Kirsch edge detector kernel.
+        /// </summary>
+        public static EdgeDetectorCompassKernel Kirsch { get; } = EdgeDetectorCompassKernel.Kirsch;
+
+        /// <summary>
+        /// Gets the Laplacian 3x3 edge detector kernel.
+        /// </summary>
+        public static EdgeDetectorKernel Laplacian3x3 { get; } = EdgeDetectorKernel.Laplacian3x3;
+
+        /// <summary>
+        /// Gets the Laplacian 5x5 edge detector kernel.
+        /// </summary>
+        public static EdgeDetectorKernel Laplacian5x5 { get; } = EdgeDetectorKernel.Laplacian5x5;
+
+        /// <summary>
+        /// Gets the Laplacian of Gaussian edge detector kernel.
+        /// </summary>
+        public static EdgeDetectorKernel LaplacianOfGaussian { get; } = EdgeDetectorKernel.LaplacianOfGaussian;
+
+        /// <summary>
+        /// Gets the Prewitt edge detector kernel.
+        /// </summary>
+        public static EdgeDetector2DKernel Prewitt { get; } = EdgeDetector2DKernel.PrewittKernel;
+
+        /// <summary>
+        /// Gets the Roberts-Cross edge detector kernel.
+        /// </summary>
+        public static EdgeDetector2DKernel RobertsCross { get; } = EdgeDetector2DKernel.RobertsCrossKernel;
+
+        /// <summary>
+        /// Gets the Robinson edge detector kernel.
+        /// </summary>
+        public static EdgeDetectorCompassKernel Robinson { get; } = EdgeDetectorCompassKernel.Robinson;
+
+        /// <summary>
+        /// Gets the Scharr edge detector kernel.
+        /// </summary>
+        public static EdgeDetector2DKernel Scharr { get; } = EdgeDetector2DKernel.ScharrKernel;
+
+        /// <summary>
+        /// Gets the Sobel edge detector kernel.
+        /// </summary>
+        public static EdgeDetector2DKernel Sobel { get; } = EdgeDetector2DKernel.SobelKernel;
+    }
+}

src/ImageSharp/Processing/Processors/Convolution/EdgeDetectorCompassProcessor{TPixel}.cs

@@ -18,25 +18,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
     internal class EdgeDetectorCompassProcessor<TPixel> : ImageProcessor<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>
     {
+        private readonly DenseMatrix<float>[] kernels;
+        private readonly bool grayscale;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="EdgeDetectorCompassProcessor{TPixel}"/> class.
         /// </summary>
         /// <param name="configuration">The configuration which allows altering default behaviour or extending the library.</param>
-        /// <param name="kernels">Gets the kernels to use.</param>
+        /// <param name="kernels">The kernels to use.</param>
         /// <param name="grayscale">Whether to convert the image to grayscale before performing edge detection.</param>
         /// <param name="source">The source <see cref="Image{TPixel}"/> for the current processor instance.</param>
         /// <param name="sourceRectangle">The source area to process for the current processor instance.</param>
-        internal EdgeDetectorCompassProcessor(Configuration configuration, CompassKernels kernels, bool grayscale, Image<TPixel> source, Rectangle sourceRectangle)
+        internal EdgeDetectorCompassProcessor(Configuration configuration, in EdgeDetectorCompassKernel kernels, bool grayscale, Image<TPixel> source, Rectangle sourceRectangle)
             : base(configuration, source, sourceRectangle)
         {
-            this.Grayscale = grayscale;
+            this.grayscale = grayscale;
-            this.Kernels = kernels;
+            this.kernels = kernels.Flatten();
         }
 
-        private CompassKernels Kernels { get; }
-
-        private bool Grayscale { get; }
-
         /// <inheritdoc/>
         protected override void BeforeImageApply()
         {
@@ -45,7 +44,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
                 opaque.Execute();
             }
 
-            if (this.Grayscale)
+            if (this.grayscale)
             {
                 new GrayscaleBt709Processor(1F).Execute(this.Configuration, this.Source, this.SourceRectangle);
             }
@@ -56,29 +55,27 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <inheritdoc />
         protected override void OnFrameApply(ImageFrame<TPixel> source)
         {
-            DenseMatrix<float>[] kernels = this.Kernels.Flatten();
-
             var interest = Rectangle.Intersect(this.SourceRectangle, source.Bounds());
 
             // We need a clean copy for each pass to start from
             using ImageFrame<TPixel> cleanCopy = source.Clone();
 
-            using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[0], true, this.Source, interest))
+            using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, in this.kernels[0], true, this.Source, interest))
             {
                 processor.Apply(source);
             }
 
-            if (kernels.Length == 1)
+            if (this.kernels.Length == 1)
             {
                 return;
             }
 
             // Additional runs
-            for (int i = 1; i < kernels.Length; i++)
+            for (int i = 1; i < this.kernels.Length; i++)
             {
                 using ImageFrame<TPixel> pass = cleanCopy.Clone();
 
-                using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, kernels[i], true, this.Source, interest))
+                using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, in this.kernels[i], true, this.Source, interest))
                 {
                     processor.Apply(pass);
                 }

src/ImageSharp/Processing/Processors/Convolution/EdgeDetectorProcessor{TPixel}.cs

@@ -13,6 +13,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
     internal class EdgeDetectorProcessor<TPixel> : ImageProcessor<TPixel>
         where TPixel : unmanaged, IPixel<TPixel>
     {
+        private readonly bool grayscale;
+        private readonly DenseMatrix<float> kernelXY;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="EdgeDetectorProcessor{TPixel}"/> class.
         /// </summary>
@@ -23,23 +26,16 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <param name="sourceRectangle">The target area to process for the current processor instance.</param>
         public EdgeDetectorProcessor(
             Configuration configuration,
-            in DenseMatrix<float> kernelXY,
+            in EdgeDetectorKernel kernelXY,
             bool grayscale,
             Image<TPixel> source,
             Rectangle sourceRectangle)
             : base(configuration, source, sourceRectangle)
         {
-            this.KernelXY = kernelXY;
+            this.kernelXY = kernelXY.KernelXY;
-            this.Grayscale = grayscale;
+            this.grayscale = grayscale;
         }
 
-        public bool Grayscale { get; }
-
-        /// <summary>
-        /// Gets the 2d gradient operator.
-        /// </summary>
-        public DenseMatrix<float> KernelXY { get; }
-
         /// <inheritdoc/>
         protected override void BeforeImageApply()
         {
@@ -48,7 +44,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
                 opaque.Execute();
             }
 
-            if (this.Grayscale)
+            if (this.grayscale)
             {
                 new GrayscaleBt709Processor(1F).Execute(this.Configuration, this.Source, this.SourceRectangle);
             }
@@ -59,10 +55,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <inheritdoc/>
         protected override void OnFrameApply(ImageFrame<TPixel> source)
         {
-            using (var processor = new ConvolutionProcessor<TPixel>(this.Configuration, this.KernelXY, true, this.Source, this.SourceRectangle))
+            using var processor = new ConvolutionProcessor<TPixel>(this.Configuration, in this.kernelXY, true, this.Source, this.SourceRectangle);
-            {
+            processor.Apply(source);
-                processor.Apply(source);
-            }
         }
     }
 }

src/ImageSharp/Processing/Processors/Convolution/Kernels/CompassKernels.cs

@@ -1,55 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Apache License, Version 2.0.
-
-namespace SixLabors.ImageSharp.Processing.Processors.Convolution
-{
-    internal abstract class CompassKernels
-    {
-        /// <summary>
-        /// Gets the North gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> North { get; }
-
-        /// <summary>
-        /// Gets the NorthWest gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> NorthWest { get; }
-
-        /// <summary>
-        /// Gets the West gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> West { get; }
-
-        /// <summary>
-        /// Gets the SouthWest gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> SouthWest { get; }
-
-        /// <summary>
-        /// Gets the South gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> South { get; }
-
-        /// <summary>
-        /// Gets the SouthEast gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> SouthEast { get; }
-
-        /// <summary>
-        /// Gets the East gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> East { get; }
-
-        /// <summary>
-        /// Gets the NorthEast gradient operator.
-        /// </summary>
-        public abstract DenseMatrix<float> NorthEast { get; }
-
-        public DenseMatrix<float>[] Flatten() =>
-            new[]
-                {
-                    this.North, this.NorthWest, this.West, this.SouthWest,
-                    this.South, this.SouthEast, this.East, this.NorthEast
-                };
-    }
-}

src/ImageSharp/Processing/Processors/Convolution/Kernels/EdgeDetector2DKernel.cs

@@ -0,0 +1,103 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Processing.Processors.Convolution
+{
+    /// <summary>
+    /// Represents an edge detection convolution kernel consisting of two 1D gradient operators.
+    /// </summary>
+    public readonly struct EdgeDetector2DKernel : IEquatable<EdgeDetector2DKernel>
+    {
+        /// <summary>
+        /// An edge detection kernel containing two Kayyali operators.
+        /// </summary>
+        public static EdgeDetector2DKernel KayyaliKernel = new EdgeDetector2DKernel(KayyaliKernels.KayyaliX, KayyaliKernels.KayyaliY);
+
+        /// <summary>
+        /// An edge detection kernel containing two Prewitt operators.
+        /// <see href="https://en.wikipedia.org/wiki/Prewitt_operator"/>.
+        /// </summary>
+        public static EdgeDetector2DKernel PrewittKernel = new EdgeDetector2DKernel(PrewittKernels.PrewittX, PrewittKernels.PrewittY);
+
+        /// <summary>
+        /// An edge detection kernel containing two Roberts-Cross operators.
+        /// <see href="https://en.wikipedia.org/wiki/Roberts_cross"/>.
+        /// </summary>
+        public static EdgeDetector2DKernel RobertsCrossKernel = new EdgeDetector2DKernel(RobertsCrossKernels.RobertsCrossX, RobertsCrossKernels.RobertsCrossY);
+
+        /// <summary>
+        /// An edge detection kernel containing two Scharr operators.
+        /// </summary>
+        public static EdgeDetector2DKernel ScharrKernel = new EdgeDetector2DKernel(ScharrKernels.ScharrX, ScharrKernels.ScharrY);
+
+        /// <summary>
+        /// An edge detection kernel containing two Sobel operators.
+        /// <see href="https://en.wikipedia.org/wiki/Sobel_operator"/>.
+        /// </summary>
+        public static EdgeDetector2DKernel SobelKernel = new EdgeDetector2DKernel(SobelKernels.SobelX, SobelKernels.SobelY);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EdgeDetector2DKernel"/> struct.
+        /// </summary>
+        /// <param name="kernelX">The horizontal gradient operator.</param>
+        /// <param name="kernelY">The vertical gradient operator.</param>
+        public EdgeDetector2DKernel(DenseMatrix<float> kernelX, DenseMatrix<float> kernelY)
+        {
+            Guard.IsTrue(
+                kernelX.Size.Equals(kernelY.Size),
+                $"{nameof(kernelX)} {nameof(kernelY)}",
+                "Kernel sizes must be the same.");
+
+            this.KernelX = kernelX;
+            this.KernelY = kernelY;
+        }
+
+        /// <summary>
+        /// Gets the horizontal gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelX { get; }
+
+        /// <summary>
+        /// Gets the vertical gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelY { get; }
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetector2DKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetector2DKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetector2DKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator ==(EdgeDetector2DKernel left, EdgeDetector2DKernel right)
+            => left.Equals(right);
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetector2DKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetector2DKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetector2DKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator !=(EdgeDetector2DKernel left, EdgeDetector2DKernel right)
+            => !(left == right);
+
+        /// <inheritdoc/>
+        public override bool Equals(object obj)
+            => obj is EdgeDetector2DKernel kernel && this.Equals(kernel);
+
+        /// <inheritdoc/>
+        public bool Equals(EdgeDetector2DKernel other)
+            => this.KernelX.Equals(other.KernelX)
+            && this.KernelY.Equals(other.KernelY);
+
+        /// <inheritdoc/>
+        public override int GetHashCode() => HashCode.Combine(this.KernelX, this.KernelY);
+    }
+}

src/ImageSharp/Processing/Processors/Convolution/Kernels/EdgeDetectorCompassKernel.cs

@@ -0,0 +1,161 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Processing.Processors.Convolution
+{
+    /// <summary>
+    /// Represents an edge detection convolution kernel consisting of eight gradient operators.
+    /// </summary>
+    public readonly struct EdgeDetectorCompassKernel : IEquatable<EdgeDetectorCompassKernel>
+    {
+        /// <summary>
+        /// An edge detection kenel comprised of Kirsch gradient operators.
+        /// </summary>
+        public static EdgeDetectorCompassKernel Kirsch =
+            new EdgeDetectorCompassKernel(
+                KirschKernels.North,
+                KirschKernels.NorthWest,
+                KirschKernels.West,
+                KirschKernels.SouthWest,
+                KirschKernels.South,
+                KirschKernels.SouthEast,
+                KirschKernels.East,
+                KirschKernels.NorthEast);
+
+        /// <summary>
+        /// An edge detection kenel comprised of Robinson gradient operators.
+        /// </summary>
+        public static EdgeDetectorCompassKernel Robinson =
+            new EdgeDetectorCompassKernel(
+                RobinsonKernels.North,
+                RobinsonKernels.NorthWest,
+                RobinsonKernels.West,
+                RobinsonKernels.SouthWest,
+                RobinsonKernels.South,
+                RobinsonKernels.SouthEast,
+                RobinsonKernels.East,
+                RobinsonKernels.NorthEast);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EdgeDetectorCompassKernel"/> struct.
+        /// </summary>
+        /// <param name="north">The north gradient operator.</param>
+        /// <param name="northWest">The north-west gradient operator.</param>
+        /// <param name="west">The west gradient operator.</param>
+        /// <param name="southWest">The south-west gradient operator.</param>
+        /// <param name="south">The south gradient operator.</param>
+        /// <param name="southEast">The south-east gradient operator.</param>
+        /// <param name="east">The east gradient operator.</param>
+        /// <param name="northEast">The north-east gradient operator.</param>
+        public EdgeDetectorCompassKernel(
+            DenseMatrix<float> north,
+            DenseMatrix<float> northWest,
+            DenseMatrix<float> west,
+            DenseMatrix<float> southWest,
+            DenseMatrix<float> south,
+            DenseMatrix<float> southEast,
+            DenseMatrix<float> east,
+            DenseMatrix<float> northEast)
+        {
+            this.North = north;
+            this.NorthWest = northWest;
+            this.West = west;
+            this.SouthWest = southWest;
+            this.South = south;
+            this.SouthEast = southEast;
+            this.East = east;
+            this.NorthEast = northEast;
+        }
+
+        /// <summary>
+        /// Gets the North gradient operator.
+        /// </summary>
+        public DenseMatrix<float> North { get; }
+
+        /// <summary>
+        /// Gets the NorthWest gradient operator.
+        /// </summary>
+        public DenseMatrix<float> NorthWest { get; }
+
+        /// <summary>
+        /// Gets the West gradient operator.
+        /// </summary>
+        public DenseMatrix<float> West { get; }
+
+        /// <summary>
+        /// Gets the SouthWest gradient operator.
+        /// </summary>
+        public DenseMatrix<float> SouthWest { get; }
+
+        /// <summary>
+        /// Gets the South gradient operator.
+        /// </summary>
+        public DenseMatrix<float> South { get; }
+
+        /// <summary>
+        /// Gets the SouthEast gradient operator.
+        /// </summary>
+        public DenseMatrix<float> SouthEast { get; }
+
+        /// <summary>
+        /// Gets the East gradient operator.
+        /// </summary>
+        public DenseMatrix<float> East { get; }
+
+        /// <summary>
+        /// Gets the NorthEast gradient operator.
+        /// </summary>
+        public DenseMatrix<float> NorthEast { get; }
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetectorCompassKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetectorCompassKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetectorCompassKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator ==(EdgeDetectorCompassKernel left, EdgeDetectorCompassKernel right)
+            => left.Equals(right);
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetectorCompassKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetectorCompassKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetectorCompassKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator !=(EdgeDetectorCompassKernel left, EdgeDetectorCompassKernel right)
+            => !(left == right);
+
+        /// <inheritdoc/>
+        public override bool Equals(object obj) => obj is EdgeDetectorCompassKernel kernel && this.Equals(kernel);
+
+        /// <inheritdoc/>
+        public bool Equals(EdgeDetectorCompassKernel other) => this.North.Equals(other.North) && this.NorthWest.Equals(other.NorthWest) && this.West.Equals(other.West) && this.SouthWest.Equals(other.SouthWest) && this.South.Equals(other.South) && this.SouthEast.Equals(other.SouthEast) && this.East.Equals(other.East) && this.NorthEast.Equals(other.NorthEast);
+
+        /// <inheritdoc/>
+        public override int GetHashCode()
+            => HashCode.Combine(
+                this.North,
+                this.NorthWest,
+                this.West,
+                this.SouthWest,
+                this.South,
+                this.SouthEast,
+                this.East,
+                this.NorthEast);
+
+        internal DenseMatrix<float>[] Flatten() =>
+             new[]
+                 {
+                    this.North, this.NorthWest, this.West, this.SouthWest,
+                    this.South, this.SouthEast, this.East, this.NorthEast
+                 };
+    }
+}

src/ImageSharp/Processing/Processors/Convolution/Kernels/EdgeDetectorKernel.cs

@@ -0,0 +1,75 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+
+namespace SixLabors.ImageSharp.Processing.Processors.Convolution
+{
+    /// <summary>
+    /// Represents an edge detection convolution kernel consisting of a single 2D gradient operator.
+    /// </summary>
+    public readonly struct EdgeDetectorKernel : IEquatable<EdgeDetectorKernel>
+    {
+        /// <summary>
+        /// An edge detection kernel containing a 3x3 Laplacian operator.
+        /// </summary>
+        public static EdgeDetectorKernel Laplacian3x3 = new EdgeDetectorKernel(LaplacianKernels.Laplacian3x3);
+
+        /// <summary>
+        /// An edge detection kernel containing a 5x5 Laplacian operator.
+        /// </summary>
+        public static EdgeDetectorKernel Laplacian5x5 = new EdgeDetectorKernel(LaplacianKernels.Laplacian5x5);
+
+        /// <summary>
+        /// An edge detection kernel containing a Laplacian of Gaussian operator.
+        /// </summary>
+        public static EdgeDetectorKernel LaplacianOfGaussian = new EdgeDetectorKernel(LaplacianKernels.LaplacianOfGaussianXY);
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EdgeDetectorKernel"/> struct.
+        /// </summary>
+        /// <param name="kernelXY">The 2D gradient operator.</param>
+        public EdgeDetectorKernel(DenseMatrix<float> kernelXY)
+            => this.KernelXY = kernelXY;
+
+        /// <summary>
+        /// Gets the 2D gradient operator.
+        /// </summary>
+        public DenseMatrix<float> KernelXY { get; }
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetectorKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetectorKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetectorKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator ==(EdgeDetectorKernel left, EdgeDetectorKernel right)
+            => left.Equals(right);
+
+        /// <summary>
+        /// Checks whether two <see cref="EdgeDetectorKernel"/> structures are equal.
+        /// </summary>
+        /// <param name="left">The left hand <see cref="EdgeDetectorKernel"/> operand.</param>
+        /// <param name="right">The right hand <see cref="EdgeDetectorKernel"/> operand.</param>
+        /// <returns>
+        /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter;
+        /// otherwise, false.
+        /// </returns>
+        public static bool operator !=(EdgeDetectorKernel left, EdgeDetectorKernel right)
+            => !(left == right);
+
+        /// <inheritdoc/>
+        public override bool Equals(object obj)
+            => obj is EdgeDetectorKernel kernel && this.Equals(kernel);
+
+        /// <inheritdoc/>
+        public bool Equals(EdgeDetectorKernel other)
+            => this.KernelXY.Equals(other.KernelXY);
+
+        /// <inheritdoc/>
+        public override int GetHashCode() => this.KernelXY.GetHashCode();
+    }
+}

src/ImageSharp/Processing/Processors/Convolution/Kernels/KirschKernels.cs → src/ImageSharp/Processing/Processors/Convolution/Kernels/Implementation/KirschKernels.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 namespace SixLabors.ImageSharp.Processing.Processors.Convolution
@@ -6,12 +6,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
     /// <summary>
     /// Contains the eight matrices used for Kirsch edge detection
     /// </summary>
-    internal class KirschKernels : CompassKernels
+    internal static class KirschKernels
     {
         /// <summary>
         /// Gets the North gradient operator
         /// </summary>
-        public override DenseMatrix<float> North =>
+        public static DenseMatrix<float> North =>
             new float[,]
             {
                { 5,  5,  5 },
@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the NorthWest gradient operator
         /// </summary>
-        public override DenseMatrix<float> NorthWest =>
+        public static DenseMatrix<float> NorthWest =>
             new float[,]
             {
                { 5,  5, -3 },
@@ -33,7 +33,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the West gradient operator
         /// </summary>
-        public override DenseMatrix<float> West =>
+        public static DenseMatrix<float> West =>
             new float[,]
             {
                { 5, -3, -3 },
@@ -44,7 +44,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the SouthWest gradient operator
         /// </summary>
-        public override DenseMatrix<float> SouthWest =>
+        public static DenseMatrix<float> SouthWest =>
             new float[,]
             {
                { -3, -3, -3 },
@@ -55,7 +55,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the South gradient operator
         /// </summary>
-        public override DenseMatrix<float> South =>
+        public static DenseMatrix<float> South =>
             new float[,]
             {
                { -3, -3, -3 },
@@ -66,7 +66,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the SouthEast gradient operator
         /// </summary>
-        public override DenseMatrix<float> SouthEast =>
+        public static DenseMatrix<float> SouthEast =>
             new float[,]
             {
                { -3, -3, -3 },
@@ -77,7 +77,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the East gradient operator
         /// </summary>
-        public override DenseMatrix<float> East =>
+        public static DenseMatrix<float> East =>
             new float[,]
             {
                { -3, -3, 5 },
@@ -88,7 +88,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the NorthEast gradient operator
         /// </summary>
-        public override DenseMatrix<float> NorthEast =>
+        public static DenseMatrix<float> NorthEast =>
             new float[,]
             {
                { -3,  5,  5 },
@@ -96,4 +96,4 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
                { -3, -3, -3 }
             };
     }
-}
+}

src/ImageSharp/Processing/Processors/Convolution/Kernels/RobinsonKernels.cs → src/ImageSharp/Processing/Processors/Convolution/Kernels/Implementation/RobinsonKernels.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors.
+// Copyright (c) Six Labors.
 // Licensed under the Apache License, Version 2.0.
 
 namespace SixLabors.ImageSharp.Processing.Processors.Convolution
@@ -6,12 +6,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
     /// <summary>
     /// Contains the kernels used for Robinson edge detection.
     /// </summary>
-    internal class RobinsonKernels : CompassKernels
+    internal static class RobinsonKernels
     {
         /// <summary>
         /// Gets the North gradient operator
         /// </summary>
-        public override DenseMatrix<float> North =>
+        public static DenseMatrix<float> North =>
             new float[,]
             {
                { 1, 2, 1 },
@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the NorthWest gradient operator
         /// </summary>
-        public override DenseMatrix<float> NorthWest =>
+        public static DenseMatrix<float> NorthWest =>
             new float[,]
             {
                { 2,  1, 0 },
@@ -33,7 +33,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the West gradient operator
         /// </summary>
-        public override DenseMatrix<float> West =>
+        public static DenseMatrix<float> West =>
             new float[,]
             {
                { 1, 0, -1 },
@@ -44,7 +44,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the SouthWest gradient operator
         /// </summary>
-        public override DenseMatrix<float> SouthWest =>
+        public static DenseMatrix<float> SouthWest =>
             new float[,]
             {
                { 0, -1, -2 },
@@ -55,7 +55,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the South gradient operator
         /// </summary>
-        public override DenseMatrix<float> South =>
+        public static DenseMatrix<float> South =>
             new float[,]
             {
                { -1, -2, -1 },
@@ -66,7 +66,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the SouthEast gradient operator
         /// </summary>
-        public override DenseMatrix<float> SouthEast =>
+        public static DenseMatrix<float> SouthEast =>
             new float[,]
             {
                { -2, -1, 0 },
@@ -77,7 +77,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the East gradient operator
         /// </summary>
-        public override DenseMatrix<float> East =>
+        public static DenseMatrix<float> East =>
             new float[,]
             {
                { -1, 0, 1 },
@@ -88,7 +88,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
         /// <summary>
         /// Gets the NorthEast gradient operator
         /// </summary>
-        public override DenseMatrix<float> NorthEast =>
+        public static DenseMatrix<float> NorthEast =>
             new float[,]
             {
                { 0,  1,  2 },
@@ -96,4 +96,4 @@ namespace SixLabors.ImageSharp.Processing.Processors.Convolution
                { -2, -1, 0 }
             };
     }
-}
+}

tests/ImageSharp.Benchmarks/Samplers/DetectEdges.cs

@@ -37,17 +37,17 @@ namespace SixLabors.ImageSharp.Benchmarks
         [Benchmark(Description = "ImageSharp DetectEdges")]
         public void ImageProcessorCoreDetectEdges()
         {
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Kayyali));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Kayyali));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Kayyali));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Kayyali));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Kirsch));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Kirsch));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Laplacian3x3));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Laplacian3x3));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Laplacian5x5));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Laplacian5x5));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.LaplacianOfGaussian));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.LaplacianOfGaussian));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Prewitt));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Prewitt));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.RobertsCross));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.RobertsCross));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Robinson));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Robinson));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Scharr));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Scharr));
-            this.image.Mutate(x => x.DetectEdges(EdgeDetectionOperators.Sobel));
+            this.image.Mutate(x => x.DetectEdges(KnownEdgeDetectionOperators.Sobel));
         }
     }
 }

tests/ImageSharp.Tests/Processing/Convolution/DetectEdgesTest.cs

@@ -35,21 +35,21 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
 
         public static IEnumerable<object[]> EdgeDetectionTheoryData => new[]
         {
-            new object[] { new TestType<KayyaliProcessor>(), EdgeDetectionOperators.Kayyali },
+            new object[] { new TestType<KayyaliProcessor>(), KnownEdgeDetectionOperators.Kayyali },
-            new object[] { new TestType<KirschProcessor>(), EdgeDetectionOperators.Kirsch },
+            new object[] { new TestType<KirschProcessor>(), KnownEdgeDetectionOperators.Kirsch },
-            new object[] { new TestType<Laplacian3x3Processor>(), EdgeDetectionOperators.Laplacian3x3 },
+            new object[] { new TestType<Laplacian3x3Processor>(), KnownEdgeDetectionOperators.Laplacian3x3 },
-            new object[] { new TestType<Laplacian5x5Processor>(), EdgeDetectionOperators.Laplacian5x5 },
+            new object[] { new TestType<Laplacian5x5Processor>(), KnownEdgeDetectionOperators.Laplacian5x5 },
-            new object[] { new TestType<LaplacianOfGaussianProcessor>(), EdgeDetectionOperators.LaplacianOfGaussian },
+            new object[] { new TestType<LaplacianOfGaussianProcessor>(), KnownEdgeDetectionOperators.LaplacianOfGaussian },
-            new object[] { new TestType<PrewittProcessor>(), EdgeDetectionOperators.Prewitt },
+            new object[] { new TestType<PrewittProcessor>(), KnownEdgeDetectionOperators.Prewitt },
-            new object[] { new TestType<RobertsCrossProcessor>(), EdgeDetectionOperators.RobertsCross },
+            new object[] { new TestType<RobertsCrossProcessor>(), KnownEdgeDetectionOperators.RobertsCross },
-            new object[] { new TestType<RobinsonProcessor>(), EdgeDetectionOperators.Robinson },
+            new object[] { new TestType<RobinsonProcessor>(), KnownEdgeDetectionOperators.Robinson },
-            new object[] { new TestType<ScharrProcessor>(), EdgeDetectionOperators.Scharr },
+            new object[] { new TestType<ScharrProcessor>(), KnownEdgeDetectionOperators.Scharr },
-            new object[] { new TestType<SobelProcessor>(), EdgeDetectionOperators.Sobel },
+            new object[] { new TestType<SobelProcessor>(), KnownEdgeDetectionOperators.Sobel },
         };
 
         [Theory]
         [MemberData(nameof(EdgeDetectionTheoryData))]
-        public void DetectEdges_filter_SobelProcessorDefaultsSet<TProcessor>(TestType<TProcessor> type, EdgeDetectionOperators filter)
+        public void DetectEdges_filter_SobelProcessorDefaultsSet<TProcessor>(TestType<TProcessor> type, KnownEdgeDetectionOperators filter)
             where TProcessor : EdgeDetectorProcessor
         {
             this.operations.DetectEdges(filter);
@@ -61,7 +61,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Convolution
 
         [Theory]
         [MemberData(nameof(EdgeDetectionTheoryData))]
-        public void DetectEdges_filter_grayscale_SobelProcessorDefaultsSet<TProcessor>(TestType<TProcessor> type, EdgeDetectionOperators filter)
+        public void DetectEdges_filter_grayscale_SobelProcessorDefaultsSet<TProcessor>(TestType<TProcessor> type, KnownEdgeDetectionOperators filter)
             where TProcessor : EdgeDetectorProcessor
         {
             bool grey = (int)filter % 2 == 0;

tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs

@@ -20,18 +20,18 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Convolution
 
         public const PixelTypes CommonNonDefaultPixelTypes = PixelTypes.Rgba32 | PixelTypes.Bgra32 | PixelTypes.RgbaVector;
 
-        public static readonly TheoryData<EdgeDetectionOperators> DetectEdgesFilters = new TheoryData<EdgeDetectionOperators>
+        public static readonly TheoryData<KnownEdgeDetectionOperators> DetectEdgesFilters = new TheoryData<KnownEdgeDetectionOperators>
         {
-            EdgeDetectionOperators.Kayyali,
+            KnownEdgeDetectionOperators.Kayyali,
-            EdgeDetectionOperators.Kirsch,
+            KnownEdgeDetectionOperators.Kirsch,
-            EdgeDetectionOperators.Laplacian3x3,
+            KnownEdgeDetectionOperators.Laplacian3x3,
-            EdgeDetectionOperators.Laplacian5x5,
+            KnownEdgeDetectionOperators.Laplacian5x5,
-            EdgeDetectionOperators.LaplacianOfGaussian,
+            KnownEdgeDetectionOperators.LaplacianOfGaussian,
-            EdgeDetectionOperators.Prewitt,
+            KnownEdgeDetectionOperators.Prewitt,
-            EdgeDetectionOperators.RobertsCross,
+            KnownEdgeDetectionOperators.RobertsCross,
-            EdgeDetectionOperators.Robinson,
+            KnownEdgeDetectionOperators.Robinson,
-            EdgeDetectionOperators.Scharr,
+            KnownEdgeDetectionOperators.Scharr,
-            EdgeDetectionOperators.Sobel
+            KnownEdgeDetectionOperators.Sobel
         };
 
         [Theory]
@@ -53,7 +53,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Convolution
         [Theory]
         [WithTestPatternImages(nameof(DetectEdgesFilters), 100, 100, PixelTypes.Rgba32)]
         [WithFileCollection(nameof(TestImages), nameof(DetectEdgesFilters), PixelTypes.Rgba32)]
-        public void DetectEdges_WorksWithAllFilters<TPixel>(TestImageProvider<TPixel> provider, EdgeDetectionOperators detector)
+        public void DetectEdges_WorksWithAllFilters<TPixel>(TestImageProvider<TPixel> provider, KnownEdgeDetectionOperators detector)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             bool hasAlpha = provider.SourceFileOrDescription.Contains("TestPattern");
@@ -115,7 +115,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Convolution
 
         [Theory]
         [WithFile(Tests.TestImages.Png.Bike, nameof(DetectEdgesFilters), PixelTypes.Rgba32)]
-        public void WorksWithDiscoBuffers<TPixel>(TestImageProvider<TPixel> provider, EdgeDetectionOperators detector)
+        public void WorksWithDiscoBuffers<TPixel>(TestImageProvider<TPixel> provider, KnownEdgeDetectionOperators detector)
             where TPixel : unmanaged, IPixel<TPixel>
         {
             provider.RunBufferCapacityLimitProcessorTest(