Merge remote-tracking branch 'origin/master' into af/expose-buffer-internals

src/ImageSharp/Color/Color.cs

@@ -105,7 +105,7 @@ namespace SixLabors.ImageSharp
         [MethodImpl(InliningOptions.ShortMethod)]
         public static Color FromHex(string hex)
         {
-            Rgba32 rgba = Rgba32.FromHex(hex);
+            var rgba = Rgba32.FromHex(hex);
 
             return new Color(rgba);
         }
@@ -178,7 +178,7 @@ namespace SixLabors.ImageSharp
             where TPixel : struct, IPixel<TPixel>
         {
             ReadOnlySpan<Rgba64> rgba64Span = MemoryMarshal.Cast<Color, Rgba64>(source);
-            PixelOperations<TPixel>.Instance.FromRgba64(Configuration.Default, rgba64Span, destination);
+            PixelOperations<TPixel>.Instance.FromRgba64(configuration, rgba64Span, destination);
         }
     }
-}
+}

src/ImageSharp/PixelFormats/PixelAlphaCompositionMode.cs

@@ -9,17 +9,17 @@ namespace SixLabors.ImageSharp.PixelFormats
     public enum PixelAlphaCompositionMode
     {
         /// <summary>
-        /// returns the destination over the source.
+        /// Returns the destination over the source.
         /// </summary>
         SrcOver = 0,
 
         /// <summary>
-        /// returns the source colors.
+        /// Returns the source colors.
         /// </summary>
         Src,
 
         /// <summary>
-        /// returns the source over the destination.
+        /// Returns the source over the destination.
         /// </summary>
         SrcAtop,
 

src/ImageSharp/PixelFormats/PixelBlenders/DefaultPixelBlenders.Generated.tt

@@ -68,9 +68,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         foreach(var blender in blenders) {
 
             var blender_composer= $"{blender}{composer}";
-
 #>
-            internal class <#= blender_composer#> : PixelBlender<TPixel>
+            /// <summary>
+            /// A pixel blender that implements the "<#= blender_composer#>" composition equation.
+            /// </summary>
+            public class <#= blender_composer#> : PixelBlender<TPixel>
             {
                 /// <summary>
                 /// Gets the static instance of this blender.

src/ImageSharp/PixelFormats/PixelBlenders/PorterDuffFunctions.Generated.tt

@@ -17,8 +17,6 @@
 // Note use of MethodImplOptions.NoInlining. We have tests that are failing on certain architectures when
 // AggresiveInlining is used. Confirmed on Intel i7-6600U in 64bit.
 #>
-
-using System;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 
@@ -26,9 +24,14 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
 {
     internal static partial class PorterDuffFunctions
     {
-
 <# void GeneratePixelBlenders(string blender) { #>
-
+        /// <summary>
+        /// Returns the result of the "<#=blender#>Src" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>Src(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -37,6 +40,13 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return source;
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>SrcAtop" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>SrcAtop(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -45,6 +55,13 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Atop(backdrop, source, <#=blender#>(backdrop, source));
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>SrcOver" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>SrcOver(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -53,14 +70,28 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Over(backdrop, source, <#=blender#>(backdrop, source));
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>SrcIn" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>SrcIn(Vector4 backdrop, Vector4 source, float opacity)
         {
             source.W *= opacity;
 
-            return In(backdrop, source, <#=blender#>(backdrop, source));
+            return In(backdrop, source);
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>SrcOut" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>SrcOut(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -69,12 +100,26 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Out(backdrop, source);
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>Dest" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
        [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>Dest(Vector4 backdrop, Vector4 source, float opacity)
         {
             return backdrop;
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>DestAtop" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>DestAtop(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -83,6 +128,13 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Atop(source, backdrop, <#=blender#>(source, backdrop));
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>DestOver" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>DestOver(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -91,14 +143,28 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Over(source, backdrop, <#=blender#>(source, backdrop));
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>DestIn" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>DestIn(Vector4 backdrop, Vector4 source, float opacity)
         {
             source.W *= opacity;
 
-            return In(source, backdrop, <#=blender#>(source, backdrop));
+            return In(source, backdrop);
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>DestOut" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>DestOut(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -107,6 +173,13 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Out(source, backdrop);
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>Xor" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>Xor(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -115,6 +188,13 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Xor(backdrop, source);
         }
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#>Clear" compositing equation.
+        /// </summary>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.NoInlining)]
         public static Vector4 <#=blender#>Clear(Vector4 backdrop, Vector4 source, float opacity)
         {
@@ -127,6 +207,14 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
 
 <# void GenerateGenericPixelBlender(string blender, string composer) { #>
 
+        /// <summary>
+        /// Returns the result of the "<#=blender#><#=composer#>" compositing equation.
+        /// </summary>
+        /// <typeparam name="TPixel">The pixel format.</typeparam>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="opacity">The source opacity. Range 0..1</param>
+        /// <returns>The <typeparamref name="TPixel"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static TPixel <#=blender#><#=composer#><TPixel>(TPixel backdrop, TPixel source, float opacity)
             where TPixel : struct, IPixel<TPixel>

src/ImageSharp/PixelFormats/PixelBlenders/PorterDuffFunctions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
@@ -21,11 +21,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
     internal static partial class PorterDuffFunctions
     {
         /// <summary>
-        /// Source over backdrop
+        /// Returns the result of the "Normal" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Normal(Vector4 backdrop, Vector4 source)
         {
@@ -33,11 +33,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Source multiplied by backdrop
+        /// Returns the result of the "Multiply" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Multiply(Vector4 backdrop, Vector4 source)
         {
@@ -45,11 +45,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Source added to backdrop
+        /// Returns the result of the "Add" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Add(Vector4 backdrop, Vector4 source)
         {
@@ -57,11 +57,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Source subtracted from backdrop
+        /// Returns the result of the "Subtract" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Subtract(Vector4 backdrop, Vector4 source)
         {
@@ -69,11 +69,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Complement of source multiplied by the complement of backdrop
+        /// Returns the result of the "Screen" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Screen(Vector4 backdrop, Vector4 source)
         {
@@ -81,11 +81,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Per element, chooses the smallest value of source and backdrop
+        /// Returns the result of the "Darken" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Darken(Vector4 backdrop, Vector4 source)
         {
@@ -93,11 +93,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Per element, chooses the largest value of source and backdrop
+        /// Returns the result of the "Lighten" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Lighten(Vector4 backdrop, Vector4 source)
         {
@@ -105,11 +105,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Overlays source over backdrop
+        /// Returns the result of the "Overlay" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 Overlay(Vector4 backdrop, Vector4 source)
         {
@@ -121,11 +121,11 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         }
 
         /// <summary>
-        /// Hard light effect
+        /// Returns the result of the "HardLight" compositing equation.
         /// </summary>
-        /// <param name="backdrop">Backdrop color</param>
-        /// <param name="source">Source color</param>
-        /// <returns>Output color</returns>
+        /// <param name="backdrop">The backdrop vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static Vector4 HardLight(Vector4 backdrop, Vector4 source)
         {
@@ -145,22 +145,29 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static float OverlayValueFunction(float backdrop, float source)
         {
-            return backdrop <= 0.5f ? (2 * backdrop * source) : 1 - ((2 * (1 - source)) * (1 - backdrop));
+            return backdrop <= 0.5f ? (2 * backdrop * source) : 1 - (2 * (1 - source) * (1 - backdrop));
         }
 
+        /// <summary>
+        /// Returns the result of the "Over" compositing equation.
+        /// </summary>
+        /// <param name="destination">The destination vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="blend">The amount to blend. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static Vector4 Over(Vector4 dst, Vector4 src, Vector4 blend)
+        public static Vector4 Over(Vector4 destination, Vector4 source, Vector4 blend)
         {
             // calculate weights
-            float blendW = dst.W * src.W;
-            float dstW = dst.W - blendW;
-            float srcW = src.W - blendW;
+            float blendW = destination.W * source.W;
+            float dstW = destination.W - blendW;
+            float srcW = source.W - blendW;
 
             // calculate final alpha
             float alpha = dstW + srcW + blendW;
 
             // calculate final color
-            Vector4 color = (dst * dstW) + (src * srcW) + (blend * blendW);
+            Vector4 color = (destination * dstW) + (source * srcW) + (blend * blendW);
 
             // unpremultiply
             color /= MathF.Max(alpha, Constants.Epsilon);
@@ -169,18 +176,25 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return color;
         }
 
+        /// <summary>
+        /// Returns the result of the "Atop" compositing equation.
+        /// </summary>
+        /// <param name="destination">The destination vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <param name="blend">The amount to blend. Range 0..1</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static Vector4 Atop(Vector4 dst, Vector4 src, Vector4 blend)
+        public static Vector4 Atop(Vector4 destination, Vector4 source, Vector4 blend)
         {
             // calculate weights
-            float blendW = dst.W * src.W;
-            float dstW = dst.W - blendW;
+            float blendW = destination.W * source.W;
+            float dstW = destination.W - blendW;
 
             // calculate final alpha
             float alpha = dstW + blendW;
 
             // calculate final color
-            Vector4 color = (dst * dstW) + (blend * blendW);
+            Vector4 color = (destination * dstW) + (blend * blendW);
 
             // unpremultiply
             color /= MathF.Max(alpha, Constants.Epsilon);
@@ -189,38 +203,56 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return color;
         }
 
+        /// <summary>
+        /// Returns the result of the "In" compositing equation.
+        /// </summary>
+        /// <param name="destination">The destination vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static Vector4 In(Vector4 dst, Vector4 src, Vector4 blend)
+        public static Vector4 In(Vector4 destination, Vector4 source)
         {
-            float alpha = dst.W * src.W;
+            float alpha = destination.W * source.W;
 
-            Vector4 color = src * alpha;                    // premultiply
+            Vector4 color = source * alpha;                    // premultiply
             color /= MathF.Max(alpha, Constants.Epsilon);   // unpremultiply
             color.W = alpha;
 
             return color;
         }
 
+        /// <summary>
+        /// Returns the result of the "Out" compositing equation.
+        /// </summary>
+        /// <param name="destination">The destination vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static Vector4 Out(Vector4 dst, Vector4 src)
+        public static Vector4 Out(Vector4 destination, Vector4 source)
         {
-            float alpha = (1 - dst.W) * src.W;
+            float alpha = (1 - destination.W) * source.W;
 
-            Vector4 color = src * alpha;                    // premultiply
+            Vector4 color = source * alpha;                    // premultiply
             color /= MathF.Max(alpha, Constants.Epsilon);   // unpremultiply
             color.W = alpha;
 
             return color;
         }
 
+        /// <summary>
+        /// Returns the result of the "XOr" compositing equation.
+        /// </summary>
+        /// <param name="destination">The destination vector.</param>
+        /// <param name="source">The source vector.</param>
+        /// <returns>The <see cref="Vector4"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static Vector4 Xor(Vector4 dst, Vector4 src)
+        public static Vector4 Xor(Vector4 destination, Vector4 source)
         {
-            float srcW = 1 - dst.W;
-            float dstW = 1 - src.W;
+            float srcW = 1 - destination.W;
+            float dstW = 1 - source.W;
 
-            float alpha = (src.W * srcW) + (dst.W * dstW);
-            Vector4 color = (src.W * src * srcW) + (dst.W * dst * dstW);
+            float alpha = (source.W * srcW) + (destination.W * dstW);
+            Vector4 color = (source.W * source * srcW) + (destination.W * destination * dstW);
 
             // unpremultiply
             color /= MathF.Max(alpha, Constants.Epsilon);
@@ -235,4 +267,4 @@ namespace SixLabors.ImageSharp.PixelFormats.PixelBlenders
             return Vector4.Zero;
         }
     }
-}
+}

src/ImageSharp/PixelFormats/PixelBlender{TPixel}.cs

@@ -1,10 +1,9 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using System;
 using System.Buffers;
 using System.Numerics;
-
 using SixLabors.ImageSharp.Memory;
 
 namespace SixLabors.ImageSharp.PixelFormats
@@ -13,7 +12,7 @@ namespace SixLabors.ImageSharp.PixelFormats
     /// Abstract base class for calling pixel composition functions
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixel</typeparam>
-    internal abstract class PixelBlender<TPixel>
+    public abstract class PixelBlender<TPixel>
         where TPixel : struct, IPixel<TPixel>
     {
         /// <summary>
@@ -23,64 +22,11 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="source">The source color.</param>
         /// <param name="amount">
         /// A value between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
         /// </param>
-        /// <returns>The final pixel value after composition</returns>
+        /// <returns>The final pixel value after composition.</returns>
         public abstract TPixel Blend(TPixel background, TPixel source, float amount);
 
-        /// <summary>
-        /// Blend 2 rows together.
-        /// </summary>
-        /// <param name="destination">destination span</param>
-        /// <param name="background">the background span</param>
-        /// <param name="source">the source span</param>
-        /// <param name="amount">
-        /// A value between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
-        /// </param>
-        protected abstract void BlendFunction(
-            Span<Vector4> destination,
-            ReadOnlySpan<Vector4> background,
-            ReadOnlySpan<Vector4> source,
-            float amount);
-
-        /// <summary>
-        /// Blend 2 rows together.
-        /// </summary>
-        /// <param name="destination">destination span</param>
-        /// <param name="background">the background span</param>
-        /// <param name="source">the source span</param>
-        /// <param name="amount">
-        /// A span with values between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
-        /// </param>
-        protected abstract void BlendFunction(
-            Span<Vector4> destination,
-            ReadOnlySpan<Vector4> background,
-            ReadOnlySpan<Vector4> source,
-            ReadOnlySpan<float> amount);
-
-        /// <summary>
-        /// Blends 2 rows together
-        /// </summary>
-        /// <param name="configuration"><see cref="Configuration"/> to use internally</param>
-        /// <param name="destination">the destination span</param>
-        /// <param name="background">the background span</param>
-        /// <param name="source">the source span</param>
-        /// <param name="amount">
-        /// A span with values between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
-        /// </param>
-        public void Blend(
-            Configuration configuration,
-            Span<TPixel> destination,
-            ReadOnlySpan<TPixel> background,
-            ReadOnlySpan<TPixel> source,
-            ReadOnlySpan<float> amount)
-        {
-            this.Blend<TPixel>(configuration, destination, background, source, amount);
-        }
-
         /// <summary>
         /// Blends 2 rows together
         /// </summary>
@@ -90,20 +36,20 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="background">the background span</param>
         /// <param name="source">the source span</param>
         /// <param name="amount">
-        /// A span with values between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
+        /// A value between 0 and 1 indicating the weight of the second source vector.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
         /// </param>
         public void Blend<TPixelSrc>(
             Configuration configuration,
             Span<TPixel> destination,
             ReadOnlySpan<TPixel> background,
             ReadOnlySpan<TPixelSrc> source,
-            ReadOnlySpan<float> amount)
+            float amount)
             where TPixelSrc : struct, IPixel<TPixelSrc>
         {
             Guard.MustBeGreaterThanOrEqualTo(background.Length, destination.Length, nameof(background.Length));
             Guard.MustBeGreaterThanOrEqualTo(source.Length, destination.Length, nameof(source.Length));
-            Guard.MustBeGreaterThanOrEqualTo(amount.Length, destination.Length, nameof(amount.Length));
+            Guard.MustBeBetweenOrEqualTo(amount, 0, 1, nameof(amount));
 
             using (IMemoryOwner<Vector4> buffer =
                 configuration.MemoryAllocator.Allocate<Vector4>(destination.Length * 3))
@@ -124,6 +70,25 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
         }
 
+        /// <summary>
+        /// Blends 2 rows together
+        /// </summary>
+        /// <param name="configuration"><see cref="Configuration"/> to use internally</param>
+        /// <param name="destination">the destination span</param>
+        /// <param name="background">the background span</param>
+        /// <param name="source">the source span</param>
+        /// <param name="amount">
+        /// A span with values between 0 and 1 indicating the weight of the second source vector.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
+        /// </param>
+        public void Blend(
+            Configuration configuration,
+            Span<TPixel> destination,
+            ReadOnlySpan<TPixel> background,
+            ReadOnlySpan<TPixel> source,
+            ReadOnlySpan<float> amount)
+            => this.Blend<TPixel>(configuration, destination, background, source, amount);
+
         /// <summary>
         /// Blends 2 rows together
         /// </summary>
@@ -133,20 +98,20 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="background">the background span</param>
         /// <param name="source">the source span</param>
         /// <param name="amount">
-        /// A value between 0 and 1 indicating the weight of the second source vector.
-        /// At amount = 0, "from" is returned, at amount = 1, "to" is returned.
+        /// A span with values between 0 and 1 indicating the weight of the second source vector.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
         /// </param>
         public void Blend<TPixelSrc>(
             Configuration configuration,
             Span<TPixel> destination,
             ReadOnlySpan<TPixel> background,
             ReadOnlySpan<TPixelSrc> source,
-            float amount)
+            ReadOnlySpan<float> amount)
             where TPixelSrc : struct, IPixel<TPixelSrc>
         {
             Guard.MustBeGreaterThanOrEqualTo(background.Length, destination.Length, nameof(background.Length));
             Guard.MustBeGreaterThanOrEqualTo(source.Length, destination.Length, nameof(source.Length));
-            Guard.MustBeBetweenOrEqualTo(amount, 0, 1, nameof(amount));
+            Guard.MustBeGreaterThanOrEqualTo(amount.Length, destination.Length, nameof(amount.Length));
 
             using (IMemoryOwner<Vector4> buffer =
                 configuration.MemoryAllocator.Allocate<Vector4>(destination.Length * 3))
@@ -166,5 +131,37 @@ namespace SixLabors.ImageSharp.PixelFormats
                 PixelOperations<TPixel>.Instance.FromVector4Destructive(configuration, sourceVectors, destination, PixelConversionModifiers.Scale);
             }
         }
+
+        /// <summary>
+        /// Blend 2 rows together.
+        /// </summary>
+        /// <param name="destination">destination span</param>
+        /// <param name="background">the background span</param>
+        /// <param name="source">the source span</param>
+        /// <param name="amount">
+        /// A value between 0 and 1 indicating the weight of the second source vector.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
+        /// </param>
+        protected abstract void BlendFunction(
+            Span<Vector4> destination,
+            ReadOnlySpan<Vector4> background,
+            ReadOnlySpan<Vector4> source,
+            float amount);
+
+        /// <summary>
+        /// Blend 2 rows together.
+        /// </summary>
+        /// <param name="destination">destination span</param>
+        /// <param name="background">the background span</param>
+        /// <param name="source">the source span</param>
+        /// <param name="amount">
+        /// A span with values between 0 and 1 indicating the weight of the second source vector.
+        /// At amount = 0, "background" is returned, at amount = 1, "source" is returned.
+        /// </param>
+        protected abstract void BlendFunction(
+            Span<Vector4> destination,
+            ReadOnlySpan<Vector4> background,
+            ReadOnlySpan<Vector4> source,
+            ReadOnlySpan<float> amount);
     }
-}
+}

src/ImageSharp/PixelFormats/PixelOperations{TPixel}.PixelBenders.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Six Labors and contributors.
+// Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
 using SixLabors.ImageSharp.PixelFormats.PixelBlenders;
@@ -16,7 +16,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// </summary>
         /// <param name="options">the blending and composition to apply</param>
         /// <returns>A <see cref="PixelBlender{TPixel}"/>.</returns>
-        internal PixelBlender<TPixel> GetPixelBlender(GraphicsOptions options)
+        public PixelBlender<TPixel> GetPixelBlender(GraphicsOptions options)
         {
             return this.GetPixelBlender(options.ColorBlendingMode, options.AlphaCompositionMode);
         }
@@ -27,7 +27,7 @@ namespace SixLabors.ImageSharp.PixelFormats
         /// <param name="colorMode">The color blending mode to apply</param>
         /// <param name="alphaMode">The alpha composition mode to apply</param>
         /// <returns>A <see cref="PixelBlender{TPixel}"/>.</returns>
-        internal virtual PixelBlender<TPixel> GetPixelBlender(PixelColorBlendingMode colorMode, PixelAlphaCompositionMode alphaMode)
+        public virtual PixelBlender<TPixel> GetPixelBlender(PixelColorBlendingMode colorMode, PixelAlphaCompositionMode alphaMode)
         {
             switch (alphaMode)
             {
@@ -214,4 +214,4 @@ namespace SixLabors.ImageSharp.PixelFormats
             }
         }
     }
-}
+}