Minor optimizations

src/ImageSharp/Formats/Jpeg/Components/Decoder/ColorConverters/JpegColorConverter.cs

@@ -3,12 +3,10 @@
 
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Numerics;
 
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Tuples;
-using SixLabors.Memory;
 
 namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder.ColorConverters
 {
@@ -73,8 +71,8 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder.ColorConverters
         /// </summary>
         public static JpegColorConverter GetConverter(JpegColorSpace colorSpace, float precision)
         {
-            JpegColorConverter converter = Converters.FirstOrDefault(c => c.ColorSpace == colorSpace &&
-                                                                          c.Precision == precision);
+            JpegColorConverter converter = Array.Find(Converters, c => c.ColorSpace == colorSpace
+                                                                    && c.Precision == precision);
 
             if (converter is null)
             {

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

@@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         /// <summary>
         /// Gets the components.
         /// </summary>
-        IEnumerable<IJpegComponent> Components { get; }
+        IJpegComponent[] Components { get; }
 
         /// <summary>
         /// Gets the quantization tables, in zigzag order.

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

@@ -3,7 +3,6 @@
 
 using System;
 using System.Buffers;
-using System.Linq;
 using System.Numerics;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.Memory;
@@ -57,12 +56,18 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         {
             this.configuration = configuration;
             this.RawJpeg = rawJpeg;
-            IJpegComponent c0 = rawJpeg.Components.First();
+            IJpegComponent c0 = rawJpeg.Components[0];
             this.NumberOfPostProcessorSteps = c0.SizeInBlocks.Height / BlockRowsPerStep;
             this.PostProcessorBufferSize = new Size(c0.SizeInBlocks.Width * 8, PixelRowsPerStep);
 
             MemoryAllocator memoryAllocator = configuration.MemoryAllocator;
-            this.ComponentProcessors = rawJpeg.Components.Select(c => new JpegComponentPostProcessor(memoryAllocator, this, c)).ToArray();
+
+            this.ComponentProcessors = new JpegComponentPostProcessor[rawJpeg.Components.Length];
+            for (int i = 0; i < rawJpeg.Components.Length; i++)
+            {
+                this.ComponentProcessors[i] = new JpegComponentPostProcessor(memoryAllocator, this, rawJpeg.Components[i]);
+            }
+
             this.rgbaBuffer = memoryAllocator.Allocate<Vector4>(rawJpeg.ImageSizeInPixels.Width);
             this.colorConverter = JpegColorConverter.GetConverter(rawJpeg.ColorSpace, rawJpeg.Precision);
         }
@@ -152,7 +157,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Decoder
         {
             int maxY = Math.Min(destination.Height, this.PixelRowCounter + PixelRowsPerStep);
 
-            Buffer2D<float>[] buffers = this.ComponentProcessors.Select(cp => cp.ColorBuffer).ToArray();
+            var buffers = new Buffer2D<float>[this.ComponentProcessors.Length];
+            for (int i = 0; i < this.ComponentProcessors.Length; i++)
+            {
+                buffers[i] = this.ComponentProcessors[i].ColorBuffer;
+            }
 
             for (int yy = this.PixelRowCounter; yy < maxY; yy++)
             {

src/ImageSharp/Formats/Jpeg/JpegDecoderCore.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Buffers.Binary;
-using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
@@ -169,7 +168,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg
         public JpegComponent[] Components => this.Frame.Components;
 
         /// <inheritdoc/>
-        IEnumerable<IJpegComponent> IRawJpegData.Components => this.Components;
+        IJpegComponent[] IRawJpegData.Components => this.Components;
 
         /// <inheritdoc/>
         public Block8x8F[] QuantizationTables { get; private set; }