Fix #390

src/ImageSharp/Image/PixelArea{TPixel}.cs

@@ -30,7 +30,7 @@ namespace SixLabors.ImageSharp
         /// <summary>
         /// The underlying buffer containing the raw pixel data.
         /// </summary>
-        private Buffer<byte> byteBuffer;
+        private readonly Buffer<byte> byteBuffer;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="PixelArea{TPixel}"/> class.
@@ -116,7 +116,7 @@ namespace SixLabors.ImageSharp
             this.RowStride = (width * GetComponentCount(componentOrder)) + padding;
             this.Length = this.RowStride * height;
 
-            this.byteBuffer = new Buffer<byte>(this.Length);
+            this.byteBuffer = Buffer<byte>.CreateClean(this.Length);
         }
 
         /// <summary>

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

@@ -10,12 +10,15 @@ using Xunit;
 // ReSharper disable InconsistentNaming
 namespace SixLabors.ImageSharp.Tests
 {
+    using SixLabors.ImageSharp.Advanced;
+
     public class GifDecoderTests
     {
         private const PixelTypes PixelTypes = Tests.PixelTypes.Rgba32 | Tests.PixelTypes.RgbaVector | Tests.PixelTypes.Argb32;
 
         public static readonly string[] TestFiles = { TestImages.Gif.Giphy, TestImages.Gif.Rings, TestImages.Gif.Trans };
 
+
         [Theory]
         [WithFileCollection(nameof(TestFiles), PixelTypes)]
         public void DecodeAndReSave<TPixel>(TestImageProvider<TPixel> imageProvider)
@@ -113,5 +116,21 @@ namespace SixLabors.ImageSharp.Tests
                 Assert.True(image.Frames.Count > 1);
             }
         }
+
+        [Fact]
+        public void CanDecodeIntermingledImages()
+        {
+            using (var kumin1 = Image.Load(TestFile.Create(TestImages.Gif.Kumin).Bytes))
+            using (var icon = Image.Load(TestFile.Create(TestImages.Png.Icon).Bytes))
+            using (var kumin2 = Image.Load(TestFile.Create(TestImages.Gif.Kumin).Bytes))
+            {
+                for (int i = 0; i < kumin1.Frames.Count; i++)
+                {
+                    ImageFrame<Rgba32> first = kumin1.Frames[i];
+                    ImageFrame<Rgba32> second = kumin2.Frames[i];
+                    first.ComparePixelBufferTo(second.GetPixelSpan());
+                }
+            }
+        }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -31,6 +31,7 @@ namespace SixLabors.ImageSharp.Tests
             public const string BikeGrayscale = "Png/BikeGrayscale.png";
             public const string Rgb48BppInterlaced = "Png/rgb-48bpp-interlaced.png";
             public const string SnakeGame = "Png/SnakeGame.png";
+            public const string Icon = "Png/icon.png";
 
             // Filtered test images from http://www.schaik.com/pngsuite/pngsuite_fil_png.html
             public const string Filter0 = "Png/filter0.png";
@@ -153,8 +154,9 @@ namespace SixLabors.ImageSharp.Tests
             public const string Giphy = "Gif/giphy.gif";
             public const string Cheers = "Gif/cheers.gif";
             public const string Trans = "Gif/trans.gif";
+            public const string Kumin = "Gif/kumin.gif";
 
-            public static readonly string[] All = { Rings, Giphy, Cheers, Trans };
+            public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin };
         }
     }
 }

tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs

@@ -29,7 +29,6 @@ namespace SixLabors.ImageSharp.Tests
         /// <param name="provider">The image provider</param>
         /// <param name="testOutputDetails">Details to be concatenated to the test output file, describing the parameters of the test.</param>
         /// <param name="extension">The extension</param>
-        /// <param name="grayscale">A boolean indicating whether we should save a smaller in size.</param>
         /// <param name="appendPixelTypeToFileName">A boolean indicating whether to append the pixel type to the  output file name.</param>
         public static Image<TPixel> DebugSave<TPixel>(
             this Image<TPixel> image,

tests/Images/Input/Gif/kumin.gif

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:345556b9a0e064412acc3b2ee87a9226113eb65c0a1791c2f855ac3fa1e6b7ad
+size 868269

tests/Images/Input/Png/icon.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:18f1eb7c5019153f4a0b2de90e7e0f0521193f003fabd6ac31c2f58c2562ae42
+size 4040