Actually resize a 30k x 30k image

src/ImageSharp/ImageFrame{TPixel}.cs

@@ -284,15 +284,15 @@ namespace SixLabors.ImageSharp
         /// <param name="value">The value to initialize the bitmap with.</param>
         internal void Clear(TPixel value)
         {
-            Span<TPixel> span = this.GetPixelSpan();
+            MemoryGroup<TPixel> group = this.PixelBuffer.MemoryGroup;
 
             if (value.Equals(default))
             {
-                span.Clear();
+                group.Clear();
             }
             else
             {
-                span.Fill(value);
+                group.Fill(value);
             }
         }
     }

tests/ImageSharp.Tests/Image/LargeImageIntegrationTests.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests
+{
+    public class LargeImageIntegrationTests
+    {
+        [Theory(Skip = "For local testing only.")]
+        [WithBasicTestPatternImages(width: 30000, height: 30000, PixelTypes.Rgba32)]
+        public void CreateAndResize(TestImageProvider<Rgba32> provider)
+        {
+            using Image<Rgba32> image = provider.GetImage();
+            image.Mutate(c => c.Resize(1000, 1000));
+            image.DebugSave(provider);
+        }
+    }
+}