Generics FTW!

src/ImageSharp/Processing/Extensions/Effects/PixelRowDelegateExtensions.cs

@@ -61,7 +61,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="source">The image this method extends.</param>
         /// <param name="rowOperation">The user defined processing delegate to use to modify image rows.</param>
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
-        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PositionAwarePixelRowOperation rowOperation)
+        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PixelRowOperation<Point> rowOperation)
             => ProcessPixelRowsAsVector4(source, rowOperation, PixelConversionModifiers.None);
 
         /// <summary>
@@ -71,7 +71,7 @@ namespace SixLabors.ImageSharp.Processing
         /// <param name="rowOperation">The user defined processing delegate to use to modify image rows.</param>
         /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
-        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PositionAwarePixelRowOperation rowOperation, PixelConversionModifiers modifiers)
+        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PixelRowOperation<Point> rowOperation, PixelConversionModifiers modifiers)
             => source.ApplyProcessor(new PositionAwarePixelRowDelegateProcessor(rowOperation, modifiers));
 
         /// <summary>
@@ -83,7 +83,7 @@ namespace SixLabors.ImageSharp.Processing
         /// The <see cref="Rectangle"/> structure that specifies the portion of the image object to alter.
         /// </param>
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
-        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PositionAwarePixelRowOperation rowOperation, Rectangle rectangle)
+        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PixelRowOperation<Point> rowOperation, Rectangle rectangle)
             => ProcessPixelRowsAsVector4(source, rowOperation, rectangle, PixelConversionModifiers.None);
 
         /// <summary>
@@ -96,7 +96,7 @@ namespace SixLabors.ImageSharp.Processing
         /// </param>
         /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
         /// <returns>The <see cref="IImageProcessingContext"/> to allow chaining of operations.</returns>
-        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PositionAwarePixelRowOperation rowOperation, Rectangle rectangle, PixelConversionModifiers modifiers)
+        public static IImageProcessingContext ProcessPixelRowsAsVector4(this IImageProcessingContext source, PixelRowOperation<Point> rowOperation, Rectangle rectangle, PixelConversionModifiers modifiers)
             => source.ApplyProcessor(new PositionAwarePixelRowDelegateProcessor(rowOperation, modifiers), rectangle);
     }
 }

src/ImageSharp/Processing/PixelRowOperation.cs

@@ -12,4 +12,16 @@ namespace SixLabors.ImageSharp.Processing
     /// <param name="span">The target row of <see cref="Vector4"/> pixels to process.</param>
     /// <remarks>The <see cref="Vector4.X"/>, <see cref="Vector4.Y"/>, <see cref="Vector4.Z"/>, and <see cref="Vector4.W"/> fields map the RGBA channels respectively.</remarks>
     public delegate void PixelRowOperation(Span<Vector4> span);
+
+    /// <summary>
+    /// A <see langword="delegate"/> representing a user defined processing delegate to use to modify image rows.
+    /// </summary>
+    /// <typeparam name="T">
+    /// The type of the parameter of the method that this delegate encapsulates.
+    /// This type parameter is contravariant.That is, you can use either the type you specified or any type that is less derived.
+    /// </typeparam>
+    /// <param name="span">The target row of <see cref="Vector4"/> pixels to process.</param>
+    /// <param name="value">The parameter of the method that this delegate encapsulates.</param>
+    /// <remarks>The <see cref="Vector4.X"/>, <see cref="Vector4.Y"/>, <see cref="Vector4.Z"/>, and <see cref="Vector4.W"/> fields map the RGBA channels respectively.</remarks>
+    public delegate void PixelRowOperation<in T>(Span<Vector4> span, T value);
 }

src/ImageSharp/Processing/PositionAwarePixelRowOperation.cs

@@ -1,16 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the Apache License, Version 2.0.
-
-using System;
-using System.Numerics;
-
-namespace SixLabors.ImageSharp.Processing
-{
-    /// <summary>
-    /// A <see langword="delegate"/> representing a user defined, position aware, processing delegate to use to modify image rows.
-    /// </summary>
-    /// <param name="span">The target row of <see cref="Vector4"/> pixels to process.</param>
-    /// <param name="offset">The initial horizontal and vertical offset for the input pixels to process.</param>
-    /// <remarks>The <see cref="Vector4.X"/>, <see cref="Vector4.Y"/>, <see cref="Vector4.Z"/>, and <see cref="Vector4.W"/> fields map the RGBA channels respectively.</remarks>
-    public delegate void PositionAwarePixelRowOperation(Span<Vector4> span, Point offset);
-}

src/ImageSharp/Processing/Processors/Effects/PixelRowDelegateProcessor.cs

@@ -8,7 +8,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     /// <summary>
     /// Applies a user defined row processing delegate to the image.
     /// </summary>
-    public sealed class PixelRowDelegateProcessor : IImageProcessor
+    internal sealed class PixelRowDelegateProcessor : IImageProcessor
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelRowDelegateProcessor"/> class.

src/ImageSharp/Processing/Processors/Effects/PositionAwarePixelRowDelegateProcessor.cs

@@ -8,14 +8,14 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     /// <summary>
     /// Applies a user defined, position aware, row processing delegate to the image.
     /// </summary>
-    public sealed class PositionAwarePixelRowDelegateProcessor : IImageProcessor
+    internal sealed class PositionAwarePixelRowDelegateProcessor : IImageProcessor
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="PositionAwarePixelRowDelegateProcessor"/> class.
         /// </summary>
         /// <param name="pixelRowOperation">The user defined, position aware, row processing delegate.</param>
         /// <param name="modifiers">The <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.</param>
-        public PositionAwarePixelRowDelegateProcessor(PositionAwarePixelRowOperation pixelRowOperation, PixelConversionModifiers modifiers)
+        public PositionAwarePixelRowDelegateProcessor(PixelRowOperation<Point> pixelRowOperation, PixelConversionModifiers modifiers)
         {
             this.PixelRowOperation = pixelRowOperation;
             this.Modifiers = modifiers;
@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         /// <summary>
         /// Gets the user defined, position aware, row processing delegate.
         /// </summary>
-        public PositionAwarePixelRowOperation PixelRowOperation { get; }
+        public PixelRowOperation<Point> PixelRowOperation { get; }
 
         /// <summary>
         /// Gets the <see cref="PixelConversionModifiers"/> to apply during the pixel conversions.

src/ImageSharp/Processing/Processors/Effects/PositionAwarePixelRowDelegateProcessor{TPixel}.cs

@@ -15,10 +15,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
     internal sealed class PositionAwarePixelRowDelegateProcessor<TPixel> : PixelRowDelegateProcessorBase<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
-        /// <summary>
+        private readonly PixelRowOperation<Point> pixelRowOperation;
-        /// The user defined pixel shader.
-        /// </summary>
-        private readonly PositionAwarePixelRowOperation pixelShader;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PositionAwarePixelRowDelegateProcessor{TPixel}"/> class.
@@ -30,10 +27,10 @@ namespace SixLabors.ImageSharp.Processing.Processors.Effects
         public PositionAwarePixelRowDelegateProcessor(Configuration configuration, PositionAwarePixelRowDelegateProcessor definition, Image<TPixel> source, Rectangle sourceRectangle)
             : base(configuration, definition.Modifiers, source, sourceRectangle)
         {
-            this.pixelShader = definition.PixelRowOperation;
+            this.pixelRowOperation = definition.PixelRowOperation;
         }
 
         /// <inheritdoc/>
-        protected override void ApplyPixelRowDelegate(Span<Vector4> span, Point offset) => this.pixelShader(span, offset);
+        protected override void ApplyPixelRowDelegate(Span<Vector4> span, Point offset) => this.pixelRowOperation(span, offset);
     }
 }