Moved IJpegComponent.GetBlockReference(...) to an extension method

src/ImageSharp/Formats/Jpeg/Components/Decoder/IJpegComponent.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0.
 
 using SixLabors.ImageSharp.Memory;
-using SixLabors.Memory;
 using SixLabors.Primitives;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
@@ -43,16 +42,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
 
         /// <summary>
         /// Gets the <see cref="Buffer2D{Block8x8}"/> storing the "raw" frequency-domain decoded + unzigged blocks.
-        /// We need to apply IDCT and dequantiazition to transform them into color-space blocks.
+        /// We need to apply IDCT and dequantization to transform them into color-space blocks.
         /// </summary>
         Buffer2D<Block8x8> SpectralBlocks { get; }
-
-        /// <summary>
-        /// Gets a reference to the <see cref="Block8x8"/> at the given row and column index from <see cref="SpectralBlocks"/>
-        /// </summary>
-        /// <param name="column">The column</param>
-        /// <param name="row">The row</param>
-        /// <returns>The <see cref="Block8x8"/></returns>
-        ref Block8x8 GetBlockReference(int column, int row);
     }
 }

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegComponent.cs

@@ -128,21 +128,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
                 this.SubSamplingDivisors = c0.SamplingFactors.DivideBy(this.SamplingFactors);
             }
 
-            this.SpectralBlocks = this.memoryAllocator.Allocate2D<Block8x8>(blocksPerColumnForMcu, blocksPerLineForMcu + 1, AllocationOptions.Clean);
-        }
+            int totalNumberOfBlocks = blocksPerColumnForMcu * (blocksPerLineForMcu + 1);
+            int width = this.WidthInBlocks + 1;
+            int height = totalNumberOfBlocks / width;
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ref Block8x8 GetBlockReference(int column, int row)
-        {
-            int offset = ((this.WidthInBlocks + 1) * row) + column;
-            return ref Unsafe.Add(ref MemoryMarshal.GetReference(this.SpectralBlocks.GetSpan()), offset);
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ref short GetBlockDataReference(int column, int row)
-        {
-            ref Block8x8 blockRef = ref this.GetBlockReference(column, row);
-            return ref Unsafe.As<Block8x8, short>(ref blockRef);
+            this.SpectralBlocks = this.memoryAllocator.Allocate2D<Block8x8>(width, height, AllocationOptions.Clean);
         }
     }
 }

src/ImageSharp/Formats/Jpeg/Components/Decoder/JpegComponentExtensions.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Runtime.CompilerServices;
+
+using SixLabors.ImageSharp.Memory;
+
+namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
+{
+    /// <summary>
+    /// Extension methods for <see cref="IJpegComponent"/>
+    /// </summary>
+    internal static class JpegComponentExtensions
+    {
+        /// <summary>
+        /// Gets a reference to the <see cref="Block8x8"/> at the given row and column index from <see cref="IJpegComponent.SpectralBlocks"/>
+        /// </summary>
+        /// <param name="component">The <see cref="IJpegComponent"/></param>
+        /// <param name="column">The column</param>
+        /// <param name="row">The row</param>
+        /// <returns>The <see cref="Block8x8"/></returns>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public static ref Block8x8 GetBlockReference(this IJpegComponent component, int column, int row)
+        {
+            return ref component.SpectralBlocks.GetRowSpan(row)[column];
+        }
+
+        /// <summary>
+        /// Gets a reference to the first item in a block
+        /// at the given row and column index from <see cref="IJpegComponent.SpectralBlocks"/>
+        /// </summary>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public static ref short GetBlockDataReference(this IJpegComponent component, int column, int row)
+        {
+            ref Block8x8 blockRef = ref component.GetBlockReference(column, row);
+            return ref Unsafe.As<Block8x8, short>(ref blockRef);
+        }
+    }
+}