Default RepeatCount to 1. Fix #1098

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -274,9 +274,8 @@ namespace SixLabors.ImageSharp.Formats.Gif
                 }
 
                 // Could be XMP or something else not supported yet.
-                // Back up and skip.
-                this.stream.Position -= appLength + 1;
-                this.SkipBlock(appLength);
+                // Skip the subblock and terminator.
+                this.SkipBlock(subBlockSize);
                 return;
             }
 

src/ImageSharp/Formats/Gif/GifMetadata.cs

@@ -36,10 +36,10 @@ namespace SixLabors.ImageSharp.Formats.Gif
         /// <summary>
         /// Gets or sets the number of times any animation is repeated.
         /// <remarks>
-        /// 0 means to repeat indefinitely, count is set as play n + 1 times
+        /// 0 means to repeat indefinitely, count is set as repeat n-1 times
         /// </remarks>
         /// </summary>
-        public ushort RepeatCount { get; set; }
+        public ushort RepeatCount { get; set; } = 1;
 
         /// <summary>
         /// Gets or sets the color table mode.

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

@@ -23,6 +23,14 @@ namespace SixLabors.ImageSharp.Tests.Formats.Gif
                 { TestImages.Gif.Ratio4x1, 4, 1, PixelResolutionUnit.AspectRatio }
             };
 
+        public static readonly TheoryData<string, uint> RepeatFiles =
+            new TheoryData<string, uint>
+            {
+                { TestImages.Gif.Cheers, 0 },
+                { TestImages.Gif.Receipt, 1 },
+                { TestImages.Gif.Rings, 1 }
+            };
+
         [Fact]
         public void CloneIsDeep()
         {
@@ -152,5 +160,35 @@ namespace SixLabors.ImageSharp.Tests.Formats.Gif
                 }
             }
         }
+
+        [Theory]
+        [MemberData(nameof(RepeatFiles))]
+        public void Identify_VerifyRepeatCount(string imagePath, uint repeatCount)
+        {
+            var testFile = TestFile.Create(imagePath);
+            using (var stream = new MemoryStream(testFile.Bytes, false))
+            {
+                var decoder = new GifDecoder();
+                IImageInfo image = decoder.Identify(Configuration.Default, stream);
+                GifMetadata meta = image.Metadata.GetGifMetadata();
+                Assert.Equal(repeatCount, meta.RepeatCount);
+            }
+        }
+
+        [Theory]
+        [MemberData(nameof(RepeatFiles))]
+        public void Decode_VerifyRepeatCount(string imagePath, uint repeatCount)
+        {
+            var testFile = TestFile.Create(imagePath);
+            using (var stream = new MemoryStream(testFile.Bytes, false))
+            {
+                var decoder = new GifDecoder();
+                using (Image<Rgba32> image = decoder.Decode<Rgba32>(Configuration.Default, stream))
+                {
+                    GifMetadata meta = image.Metadata.GetGifMetadata();
+                    Assert.Equal(repeatCount, meta.RepeatCount);
+                }
+            }
+        }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -353,6 +353,7 @@ namespace SixLabors.ImageSharp.Tests
             public const string Rings = "Gif/rings.gif";
             public const string Giphy = "Gif/giphy.gif";
             public const string Cheers = "Gif/cheers.gif";
+            public const string Receipt = "Gif/receipt.gif";
             public const string Trans = "Gif/trans.gif";
             public const string Kumin = "Gif/kumin.gif";
             public const string Leo = "Gif/leo.gif";

tests/Images/Input/Gif/receipt.gif

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:bac212852eee73f3c29f30be0be375e5caccbe86e5f4adfaa8c0a7a3673a91ab
+size 50686