Don't throw for bad min code, just don't decode indices.

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -378,8 +378,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 }
 
                 indices = this.Configuration.MemoryAllocator.Allocate2D<byte>(this.imageDescriptor.Width, this.imageDescriptor.Height, AllocationOptions.Clean);
-
                 this.ReadFrameIndices(indices);
+
                 Span<byte> rawColorTable = default;
                 if (localColorTable != null)
                 {

src/ImageSharp/Formats/Gif/LzwDecoder.cs

@@ -68,16 +68,20 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// <param name="pixels">The pixel array to decode to.</param>
         public void DecodePixels(int dataSize, Buffer2D<byte> pixels)
         {
-            Guard.MustBeLessThanOrEqualTo(1 << dataSize, MaxStackSize, nameof(dataSize));
+            // Calculate the clear code. The value of the clear code is 2 ^ dataSize
+            int clearCode = 1 << dataSize;
+            if (clearCode > MaxStackSize)
+            {
+                // Don't attempt to decode the frame indices.
+                // The image is most likely corrupted.
+                return;
+            }
 
             // The resulting index table length.
             int width = pixels.Width;
             int height = pixels.Height;
             int length = width * height;
 
-            // Calculate the clear code. The value of the clear code is 2 ^ dataSize
-            int clearCode = 1 << dataSize;
-
             int codeSize = dataSize + 1;
 
             // Calculate the end code

tests/ImageSharp.Tests/Formats/Gif/GifDecoderTests.cs

@@ -271,5 +271,17 @@ namespace SixLabors.ImageSharp.Tests.Formats.Gif
             image.DebugSave(provider);
             image.CompareFirstFrameToReferenceOutput(ImageComparer.Exact, provider);
         }
+
+        // https://github.com/SixLabors/ImageSharp/issues/2012
+        [Theory]
+        [WithFile(TestImages.Gif.Issues.Issue2012BadMinCode, PixelTypes.Rgba32)]
+        public void Issue2012BadMinCode<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using Image<TPixel> image = provider.GetImage();
+
+            image.DebugSave(provider);
+            image.CompareFirstFrameToReferenceOutput(ImageComparer.Exact, provider);
+        }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -453,6 +453,7 @@ namespace SixLabors.ImageSharp.Tests
                 public const string InvalidColorIndex = "Gif/issues/issue1668_invalidcolorindex.gif";
                 public const string Issue1962NoColorTable = "Gif/issues/issue1962_tiniest_gif_1st.gif";
                 public const string Issue2012EmptyXmp = "Gif/issues/issue2012_Stronghold-Crusader-Extreme-Cover.gif";
+                public const string Issue2012BadMinCode = "Gif/issues/issue2012_drona1.gif";
             }
 
             public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin, Leo, Ratio4x1, Ratio1x4 };

tests/Images/External/ReferenceOutput/GifDecoderTests/Issue2012BadMinCode_Rgba32_issue2012_drona1.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:cf4bc93479140b05b25066eb10c33fa9f82c617828a56526d47f5a8c72035ef0
+size 1871

tests/Images/Input/Gif/issues/issue2012_drona1.gif

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:cbb23b2a19e314969c6da99374ae133d834d76c3f0ab9df4a7edc9334bb065e6
+size 10508