Make Fast2DArray internal

src/ImageSharp/Common/Memory/Fast2DArray{T}.cs

@@ -13,7 +13,7 @@ namespace ImageSharp
     /// Provides fast access to 2D arrays.
     /// </summary>
     /// <typeparam name="T">The type of elements in the array.</typeparam>
-    public struct Fast2DArray<T>
+    internal struct Fast2DArray<T>
     {
         /// <summary>
         /// The 1D representation of the 2D array.

src/ImageSharp/Dithering/ErrorDiffusion/ErrorDiffuser.cs

@@ -5,12 +5,11 @@
 
 namespace ImageSharp.Dithering
 {
-    using System;
     using System.Numerics;
     using System.Runtime.CompilerServices;
 
     /// <summary>
-    /// The base class for performing effor diffusion based dithering.
+    /// The base class for performing error diffusion based dithering.
     /// </summary>
     public abstract class ErrorDiffuser : IErrorDiffuser
     {
@@ -34,19 +33,24 @@ namespace ImageSharp.Dithering
         /// </summary>
         private readonly int startingOffset;
 
+        /// <summary>
+        /// The diffusion matrix
+        /// </summary>
+        private readonly Fast2DArray<float> matrix;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ErrorDiffuser"/> class.
         /// </summary>
         /// <param name="matrix">The dithering matrix.</param>
         /// <param name="divisor">The divisor.</param>
-        protected ErrorDiffuser(Fast2DArray<float> matrix, byte divisor)
+        internal ErrorDiffuser(Fast2DArray<float> matrix, byte divisor)
         {
             Guard.NotNull(matrix, nameof(matrix));
             Guard.MustBeGreaterThan(divisor, 0, nameof(divisor));
 
-            this.Matrix = matrix;
-            this.matrixWidth = this.Matrix.Width;
-            this.matrixHeight = this.Matrix.Height;
+            this.matrix = matrix;
+            this.matrixWidth = this.matrix.Width;
+            this.matrixHeight = this.matrix.Height;
             this.divisorVector = new Vector4(divisor);
 
             this.startingOffset = 0;
@@ -62,9 +66,6 @@ namespace ImageSharp.Dithering
             }
         }
 
-        /// <inheritdoc />
-        public Fast2DArray<float> Matrix { get; }
-
         /// <inheritdoc />
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Dither<TColor>(PixelAccessor<TColor> pixels, TColor source, TColor transformed, int x, int y, int width, int height)
@@ -87,9 +88,9 @@ namespace ImageSharp.Dithering
 
                     if (matrixX > 0 && matrixX < width && matrixY > 0 && matrixY < height)
                     {
-                        float coefficient = this.Matrix[row, col];
+                        float coefficient = this.matrix[row, col];
 
-                        // Good to disable here as we are not comparing matematical output.
+                        // Good to disable here as we are not comparing mathematical output.
                         // ReSharper disable once CompareOfFloatsByEqualityOperator
                         if (coefficient == 0)
                         {

src/ImageSharp/Dithering/ErrorDiffusion/IErrorDiffuser.cs

@@ -12,11 +12,6 @@ namespace ImageSharp.Dithering
     /// </summary>
     public interface IErrorDiffuser
     {
-        /// <summary>
-        /// Gets the dithering matrix
-        /// </summary>
-        Fast2DArray<float> Matrix { get; }
-
         /// <summary>
         /// Transforms the image applying the dither matrix. This method alters the input pixels array
         /// </summary>

src/ImageSharp/Dithering/Ordered/Bayer.cs

@@ -5,13 +5,11 @@
 
 namespace ImageSharp.Dithering.Ordered
 {
-    using System;
-
     /// <summary>
     /// Applies error diffusion based dithering using the 4x4 Bayer dithering matrix.
     /// <see href="http://www.efg2.com/Lab/Library/ImageProcessing/DHALF.TXT"/>
     /// </summary>
-    public class Bayer : IOrderedDither
+    public sealed class Bayer : OrderedDither4x4
     {
         /// <summary>
         /// The threshold matrix.
@@ -26,15 +24,12 @@ namespace ImageSharp.Dithering.Ordered
                 { 255, 127, 223, 95 }
             };
 
-        /// <inheritdoc />
-        public Fast2DArray<byte> Matrix { get; } = ThresholdMatrix;
-
-        /// <inheritdoc />
-        public void Dither<TColor>(PixelAccessor<TColor> pixels, TColor source, TColor upper, TColor lower, byte[] bytes, int index, int x, int y, int width, int height)
-            where TColor : struct, IPixel<TColor>
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Bayer"/> class.
+        /// </summary>
+        public Bayer()
+            : base(ThresholdMatrix)
         {
-            source.ToXyzwBytes(bytes, 0);
-            pixels[x, y] = ThresholdMatrix[y % 3, x % 3] >= bytes[index] ? lower : upper;
         }
     }
 }

src/ImageSharp/Dithering/Ordered/IOrderedDither.cs

@@ -5,18 +5,11 @@
 
 namespace ImageSharp.Dithering
 {
-    using System;
-
     /// <summary>
     /// Encapsulates properties and methods required to perfom ordered dithering on an image.
     /// </summary>
     public interface IOrderedDither
     {
-        /// <summary>
-        /// Gets the dithering matrix
-        /// </summary>
-        Fast2DArray<byte> Matrix { get; }
-
         /// <summary>
         /// Transforms the image applying the dither matrix. This method alters the input pixels array
         /// </summary>
@@ -34,4 +27,4 @@ namespace ImageSharp.Dithering
         void Dither<TColor>(PixelAccessor<TColor> pixels, TColor source, TColor upper, TColor lower, byte[] bytes, int index, int x, int y, int width, int height)
             where TColor : struct, IPixel<TColor>;
     }
-}
+}

src/ImageSharp/Dithering/Ordered/Ordered.cs

@@ -5,13 +5,11 @@
 
 namespace ImageSharp.Dithering.Ordered
 {
-    using System;
-
     /// <summary>
     /// Applies error diffusion based dithering using the 4x4 ordered dithering matrix.
     /// <see href="https://en.wikipedia.org/wiki/Ordered_dithering"/>
     /// </summary>
-    public class Ordered : IOrderedDither
+    public sealed class Ordered : OrderedDither4x4
     {
         /// <summary>
         /// The threshold matrix.
@@ -26,15 +24,12 @@ namespace ImageSharp.Dithering.Ordered
                { 240, 112, 208, 80 }
             };
 
-        /// <inheritdoc />
-        public Fast2DArray<byte> Matrix { get; } = ThresholdMatrix;
-
-        /// <inheritdoc />
-        public void Dither<TColor>(PixelAccessor<TColor> pixels, TColor source, TColor upper, TColor lower, byte[] bytes, int index, int x, int y, int width, int height)
-            where TColor : struct, IPixel<TColor>
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Ordered"/> class.
+        /// </summary>
+        public Ordered()
+            : base(ThresholdMatrix)
         {
-            source.ToXyzwBytes(bytes, 0);
-            pixels[x, y] = ThresholdMatrix[y % 3, x % 3] >= bytes[index] ? lower : upper;
         }
     }
 }

src/ImageSharp/Dithering/Ordered/OrderedDither4x4.cs

@@ -0,0 +1,38 @@
+// <copyright file="OrderedDither4x4.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp.Dithering.Ordered
+{
+    /// <summary>
+    /// The base class for performing ordered ditheroing using a 4x4 matrix.
+    /// </summary>
+    public abstract class OrderedDither4x4 : IOrderedDither
+    {
+        /// <summary>
+        /// The dithering matrix
+        /// </summary>
+        private Fast2DArray<byte> matrix;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="OrderedDither4x4"/> class.
+        /// </summary>
+        /// <param name="matrix">The thresholding matrix. </param>
+        internal OrderedDither4x4(Fast2DArray<byte> matrix)
+        {
+            this.matrix = matrix;
+        }
+
+        /// <inheritdoc />
+        public void Dither<TColor>(PixelAccessor<TColor> pixels, TColor source, TColor upper, TColor lower, byte[] bytes, int index, int x, int y, int width, int height)
+            where TColor : struct, IPixel<TColor>
+        {
+            // TODO: This doesn't really cut it for me.
+            // I'd rather be using float but we need to add some sort of movalization vector methods to all IPixel implementations
+            // before we can do that as the vectors all cover different ranges.
+            source.ToXyzwBytes(bytes, 0);
+            pixels[x, y] = this.matrix[y % 3, x % 3] >= bytes[index] ? lower : upper;
+        }
+    }
+}