refactor ResizeKernel creation

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

@@ -25,7 +25,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
         /// <param name="memoryAllocator">The <see cref="MemoryAllocator"/> to use for allocations.</param>
         /// <param name="destinationSize">The size of the destination window</param>
         /// <param name="kernelRadius">The radius of the kernel</param>
-        public KernelMap(MemoryAllocator memoryAllocator, int destinationSize, float kernelRadius)
+        private KernelMap(MemoryAllocator memoryAllocator, int destinationSize, float kernelRadius)
         {
             this.DestinationSize = destinationSize;
             int width = (int)Math.Ceiling(kernelRadius * 2);
@@ -125,13 +125,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
         /// <summary>
         /// Slices a weights value at the given positions.
         /// </summary>
-        /// <param name="destIdx">The index in destination buffer</param>
-        /// <param name="leftIdx">The local left index value</param>
-        /// <param name="rightIdx">The local right index value</param>
-        /// <returns>The weights</returns>
-        private ResizeKernel CreateKernel(int destIdx, int leftIdx, int rightIdx)
+        private ResizeKernel CreateKernel(int destIdx, int left, int rightIdx)
         {
-            return new ResizeKernel(destIdx, leftIdx, this.data, rightIdx - leftIdx + 1);
+            int flatStartIndex = destIdx * this.data.Width;
+            int length = rightIdx - left + 1;
+            Memory<float> bufferSlice = this.data.Memory.Slice(flatStartIndex, length);
+            return new ResizeKernel(left, bufferSlice);
         }
     }
 }

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

@@ -16,42 +16,36 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
     internal struct ResizeKernel
     {
         /// <summary>
-        /// The left index for the destination row
+        /// Initializes a new instance of the <see cref="ResizeKernel"/> struct.
         /// </summary>
-        public int Left;
+        [MethodImpl(InliningOptions.ShortMethod)]
+        internal ResizeKernel(int left, Memory<float> bufferSlice)
+        {
+            this.Left = left;
+            this.BufferSlice = bufferSlice;
+        }
 
         /// <summary>
-        /// The length of the kernel
+        /// Gets the left index for the destination row
         /// </summary>
-        public int Length;
+        public int Left { get; }
 
         /// <summary>
-        /// The buffer containing the weights values.
+        /// Gets the slice of the buffer containing the weights values.
         /// </summary>
-        private readonly Memory<float> buffer;
+        public Memory<float> BufferSlice { get; }
 
         /// <summary>
-        /// Initializes a new instance of the <see cref="ResizeKernel"/> struct.
+        /// Gets the the length of the kernel
         /// </summary>
-        /// <param name="index">The destination index in the buffer</param>
-        /// <param name="left">The local left index</param>
-        /// <param name="buffer">The span</param>
-        /// <param name="length">The length of the window</param>
-        [MethodImpl(InliningOptions.ShortMethod)]
-        internal ResizeKernel(int index, int left, Buffer2D<float> buffer, int length)
-        {
-            int flatStartIndex = index * buffer.Width;
-            this.Left = left;
-            this.buffer = buffer.MemorySource.Memory.Slice(flatStartIndex, length);
-            this.Length = length;
-        }
+        public int Length => this.BufferSlice.Length;
 
         /// <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> GetValues() => this.buffer.Span;
+        public Span<float> GetValues() => this.BufferSlice.Span;
 
         /// <summary>
         /// Computes the sum of vectors in 'rowSpan' weighted by weight values, pointed by this <see cref="ResizeKernel"/> instance.