From 5ad7ae5089551f60df6fcdc78b5fdf2686b1c01b Mon Sep 17 00:00:00 2001
From: Jason Nelson <jason@carbonmade.com>
Date: Fri, 8 Jun 2018 11:50:16 -0700
Subject: [PATCH] Stackalloc bmp header

---
 src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs b/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
index 2b0c907338..e5bf6d9cb6 100644
--- a/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
+++ b/src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
@@ -66,16 +66,25 @@ namespace SixLabors.ImageSharp.Formats.Bmp
                 reserved: 0,
                 fileSize: 54 + infoHeader.ImageSize);
 
-            byte[] buffer = new byte[40]; // TODO: stackalloc
-
+#if NETCOREAPP2_1
+            Span<byte> buffer = stackalloc byte[40];
+#else
+            byte[] buffer = new byte[40];
+#endif
             fileHeader.WriteTo(buffer);
 
+#if NETCOREAPP2_1
+            stream.Write(buffer.Slice(0, BmpFileHeader.Size));
+#else
             stream.Write(buffer, 0, BmpFileHeader.Size);
-
+#endif
             infoHeader.WriteTo(buffer);
 
+#if NETCOREAPP2_1
+            stream.Write(buffer.Slice(0, 40));
+#else
             stream.Write(buffer, 0, 40);
-
+#endif
             this.WriteImage(stream, image.Frames.RootFrame);
 
             stream.Flush();