replaced some of the PixelArea usages in bmp decoder

src/ImageSharp/Formats/Bmp/BmpDecoderCore.cs

@@ -69,7 +69,9 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// </summary>
         private BmpInfoHeader infoHeader;
 
-        private Configuration configuration;
+        private readonly Configuration configuration;
+
+        private readonly MemoryManager memoryManager;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BmpDecoderCore"/> class.
@@ -79,6 +81,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         public BmpDecoderCore(Configuration configuration, IBmpDecoderOptions options)
         {
             this.configuration = configuration;
+            this.memoryManager = configuration.MemoryManager;
         }
 
         /// <summary>
@@ -432,16 +435,28 @@ namespace SixLabors.ImageSharp.Formats.Bmp
             where TPixel : struct, IPixel<TPixel>
         {
             int padding = CalculatePadding(width, 3);
-            using (var row = new PixelArea<TPixel>(width, ComponentOrder.Zyx, padding))
+
+            using (IManagedByteBuffer row = this.memoryManager.AllocatePaddedPixelRowBuffer(width, 3, padding))
             {
                 for (int y = 0; y < height; y++)
                 {
-                    row.Read(this.currentStream);
-
+                    this.currentStream.Read(row);
                     int newY = Invert(y, height, inverted);
-                    pixels.CopyFrom(row, newY);
+                    Span<TPixel> pixelSpan = pixels.GetRowSpan(newY);
+                    PixelOperations<TPixel>.Instance.PackFromBgr24Bytes(row.Span, pixelSpan, width);
                 }
             }
+
+            //using (var row = new PixelArea<TPixel>(width, ComponentOrder.Zyx, padding))
+            //{
+            //    for (int y = 0; y < height; y++)
+            //    {
+            //        row.Read(this.currentStream);
+
+            //        int newY = Invert(y, height, inverted);
+            //        pixels.CopyFrom(row, newY);
+            //    }
+            //}
         }
 
         /// <summary>

src/ImageSharp/Formats/Bmp/BmpEncoder.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Bmp
@@ -23,7 +24,7 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             where TPixel : struct, IPixel<TPixel>
         {
-            var encoder = new BmpEncoderCore(this);
+            var encoder = new BmpEncoderCore(this, image.GetMemoryManager());
             encoder.Encode(image, stream);
         }
     }

src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs

@@ -8,6 +8,8 @@ using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Formats.Bmp
 {
+    using SixLabors.ImageSharp.Memory;
+
     /// <summary>
     /// Image encoder for writing an image to a stream as a Windows bitmap.
     /// </summary>
@@ -21,14 +23,18 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         /// <summary>
         /// Gets or sets the number of bits per pixel.
         /// </summary>
-        private BmpBitsPerPixel bitsPerPixel;
+        private readonly BmpBitsPerPixel bitsPerPixel;
+
+        private readonly MemoryManager memoryManager;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BmpEncoderCore"/> class.
         /// </summary>
         /// <param name="options">The encoder options</param>
-        public BmpEncoderCore(IBmpEncoderOptions options)
+        /// <param name="memoryManager">The memory manager</param>
+        public BmpEncoderCore(IBmpEncoderOptions options, MemoryManager memoryManager)
         {
+            this.memoryManager = memoryManager;
             this.bitsPerPixel = options.BitsPerPixel;
         }
 
@@ -173,14 +179,25 @@ namespace SixLabors.ImageSharp.Formats.Bmp
         private void Write24Bit<TPixel>(EndianBinaryWriter writer, PixelAccessor<TPixel> pixels)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (PixelArea<TPixel> row = new PixelArea<TPixel>(pixels.Width, ComponentOrder.Zyx, this.padding))
+            using (IManagedByteBuffer row =
+                this.memoryManager.AllocatePaddedPixelRowBuffer(pixels.Width, 3, this.padding))
             {
                 for (int y = pixels.Height - 1; y >= 0; y--)
                 {
-                    pixels.CopyTo(row, y);
-                    writer.Write(row.Bytes, 0, row.Length);
+                    Span<TPixel> pixelSpan = pixels.GetRowSpan(y);
+                    PixelOperations<TPixel>.Instance.ToBgr24Bytes(pixelSpan, row.Span, pixelSpan.Length);
+                    writer.Write(row.Array, 0, row.Length());
                 }
             }
+
+            //using (PixelArea<TPixel> row = new PixelArea<TPixel>(pixels.Width, ComponentOrder.Zyx, this.padding))
+            //{
+            //    for (int y = pixels.Height - 1; y >= 0; y--)
+            //    {
+            //        pixels.CopyTo(row, y);
+            //        writer.Write(row.Bytes, 0, row.Length);
+            //    }
+            //}
         }
     }
 }

src/ImageSharp/Memory/BufferExtensions.cs

@@ -6,6 +6,8 @@ using System.Runtime.CompilerServices;
 
 namespace SixLabors.ImageSharp.Memory
 {
+    using System.IO;
+
     internal static class BufferExtensions
     {
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -53,5 +55,15 @@ namespace SixLabors.ImageSharp.Memory
         public static ref T DangerousGetPinnableReference<T>(this IBuffer<T> buffer)
             where T : struct =>
             ref buffer.Span.DangerousGetPinnableReference();
+
+        public static void Read(this Stream stream, IManagedByteBuffer buffer)
+        {
+            stream.Read(buffer.Array, 0, buffer.Length());
+        }
+
+        public static void Write(this Stream stream, IManagedByteBuffer buffer)
+        {
+            stream.Write(buffer.Array, 0, buffer.Length());
+        }
     }
 }

src/ImageSharp/Memory/MemoryManagerExtensions.cs

@@ -51,5 +51,23 @@
         public static Buffer2D<T> AllocateClean2D<T>(this MemoryManager memoryManager, int width, int height)
             where T : struct =>
             Allocate2D<T>(memoryManager, width, height, true);
+
+        /// <summary>
+        /// Allocates padded buffers for BMP encoder/decoder. (Replacing old PixelRow/PixelArea)
+        /// </summary>
+        /// <param name="memoryManager">The <see cref="MemoryManager"/></param>
+        /// <param name="width">Pixel count in the row</param>
+        /// <param name="pixelSizeInBytes">The pixel size in bytes, eg. 3 for RGB</param>
+        /// <param name="paddingInBytes">The padding</param>
+        /// <returns>A <see cref="IManagedByteBuffer"/></returns>
+        public static IManagedByteBuffer AllocatePaddedPixelRowBuffer(
+            this MemoryManager memoryManager,
+            int width,
+            int pixelSizeInBytes,
+            int paddingInBytes)
+        {
+            int length = (width * pixelSizeInBytes) + paddingInBytes;
+            return memoryManager.AllocateManagedByteBuffer(length);
+        }
     }
 }

tests/ImageSharp.Tests/Formats/Bmp/BmpEncoderTests.cs

@@ -15,8 +15,6 @@ namespace SixLabors.ImageSharp.Tests
 
     public class BmpEncoderTests : FileTestBase
     {
-        private const PixelTypes PixelTypesToTest = PixelTypes.Rgba32 | PixelTypes.Bgra32 | PixelTypes.Rgb24;
-
         public static readonly TheoryData<BmpBitsPerPixel> BitsPerPixel =
             new TheoryData<BmpBitsPerPixel>
                 {