Add a test case for DangerousGetPinnableReferenceToPixelBuffer.

tests/ImageSharp.Tests/Advanced/ImageExtensionsTests.cs

@@ -0,0 +1,39 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using Xunit;
+using SixLabors.ImageSharp.Advanced;
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp.Tests.Advanced
+{
+    public class ImageExtensionsTests
+    {
+        [Fact]
+        public unsafe void DangerousGetPinnableReference_CopyToBuffer()
+        {
+            var image = new Image<Rgba32>(128, 128);
+            for (int y = 0; y < image.Height; y++)
+                for (int x = 0; x < image.Width; x++)
+                {
+                    image[x, y] = new Rgba32(x, 255 - y, x + y);
+                }
+
+            Rgba32[] targetBuffer = new Rgba32[image.Width * image.Height];
+
+            fixed (Rgba32* targetPtr = targetBuffer)
+            fixed (Rgba32* pixelBasePtr = &image.DangerousGetPinnableReferenceToPixelBuffer())
+            {
+                uint dataSizeInBytes = (uint)(image.Width * image.Height * Unsafe.SizeOf<Rgba32>());
+                Unsafe.CopyBlock(targetPtr, pixelBasePtr, dataSizeInBytes);
+            }
+
+            for (int y = 0; y < image.Height; y++)
+                for (int x = 0; x < image.Width; x++)
+                {
+                    int linearIndex = y * image.Width + x;
+                    Assert.Equal(image[x, y], targetBuffer[linearIndex]);
+                }
+        }
+    }
+}