minor refactor on ResizeKernel

src/ImageSharp/Processing/Processors/Transforms/KernelMap.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 
 using SixLabors.ImageSharp.Memory;
 using SixLabors.Memory;
@@ -89,7 +90,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
                 ResizeKernel ws = result.CreateKernel(i, left, right);
                 result.Kernels[i] = ws;
 
-                ref float weightsBaseRef = ref ws.GetStartReference();
+                ref float weightsBaseRef = ref MemoryMarshal.GetReference(ws.GetValues());
 
                 for (int j = left; j <= right; j++)
                 {

src/ImageSharp/Processing/Processors/Transforms/ResizeKernel.cs

@@ -2,13 +2,11 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Buffers;
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 
 using SixLabors.ImageSharp.Memory;
-using SixLabors.Memory;
 
 namespace SixLabors.ImageSharp.Processing.Processors.Transforms
 {
@@ -18,12 +16,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
     internal struct ResizeKernel
     {
         /// <summary>
-        /// The local left index position
+        /// The left index for the destination row
         /// </summary>
         public int Left;
 
         /// <summary>
-        /// The length of the weights window
+        /// The length of the kernel
         /// </summary>
         public int Length;
 
@@ -48,34 +46,22 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             this.Length = length;
         }
 
-        /// <summary>
-        /// Gets a reference to the first item of the window.
-        /// </summary>
-        /// <returns>The reference to the first item of the window</returns>
-        [MethodImpl(InliningOptions.ShortMethod)]
-        public ref float GetStartReference()
-        {
-            Span<float> span = this.buffer.Span;
-            return ref span[0];
-        }
-
         /// <summary>
         /// Gets the span representing the portion of the <see cref="KernelMap"/> that this window covers
         /// </summary>
         /// <returns>The <see cref="Span{T}"/></returns>
         [MethodImpl(InliningOptions.ShortMethod)]
-        public Span<float> GetSpan() => this.buffer.Span;
+        public Span<float> GetValues() => this.buffer.Span;
 
         /// <summary>
         /// Computes the sum of vectors in 'rowSpan' weighted by weight values, pointed by this <see cref="ResizeKernel"/> instance.
         /// </summary>
         /// <param name="rowSpan">The input span of vectors</param>
-        /// <param name="sourceX">The source row position.</param>
         /// <returns>The weighted sum</returns>
         [MethodImpl(InliningOptions.ShortMethod)]
         public Vector4 Convolve(Span<Vector4> rowSpan)
         {
-            ref float horizontalValues = ref this.GetStartReference();
+            ref float horizontalValues = ref MemoryMarshal.GetReference(this.GetValues());
             int left = this.Left;
             ref Vector4 vecPtr = ref Unsafe.Add(ref MemoryMarshal.GetReference(rowSpan), left);
 

tests/ImageSharp.Tests/Processing/Processors/Transforms/KernelMapTests.cs

@@ -21,10 +21,11 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
             this.Output = output;
         }
         
-        [Theory(Skip = "TODO: Add asserionts")]
+        [Theory]
         [InlineData(500, 200, nameof(KnownResamplers.Bicubic))]
         [InlineData(50, 40, nameof(KnownResamplers.Bicubic))]
         [InlineData(40, 30, nameof(KnownResamplers.Bicubic))]
+        [InlineData(15, 10, nameof(KnownResamplers.Bicubic))]
         [InlineData(500, 200, nameof(KnownResamplers.Lanczos8))]
         [InlineData(100, 80, nameof(KnownResamplers.Lanczos8))]
         [InlineData(100, 10, nameof(KnownResamplers.Lanczos8))]
@@ -37,14 +38,15 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
 
             var bld = new StringBuilder();
 
-            foreach (ResizeKernel window in kernelMap.Kernels)
+            foreach (ResizeKernel kernel in kernelMap.Kernels)
             {
-                Span<float> span = window.GetSpan();
+                bld.Append($"({kernel.Left:D3}) || ");
-                for (int i = 0; i < window.Length; i++)
+                Span<float> span = kernel.GetValues();
+                for (int i = 0; i < kernel.Length; i++)
                 {
                     float value = span[i];
-                    bld.Append($"{value,7:F4}");
+                    bld.Append($"{value,7:F5}");
-                    bld.Append("| ");
+                    bld.Append(" | ");
                 }
 
                 bld.AppendLine();