Backported #2701 (fixes #2638) to release 2.1.x

Author: Visual-Vincent

src/ImageSharp/Formats/Jpeg/Components/Decoder/HuffmanScanBuffer.cs

@@ -22,6 +22,9 @@ internal struct HuffmanScanBuffer
         // Whether there is no more good data to pull from the stream for the current mcu.
         private bool badData;
 
+        // How many times have we hit the eof.
+        private int eofHitCount;
+
         public HuffmanScanBuffer(BufferedReadStream stream)
         {
             this.stream = stream;
@@ -31,6 +34,7 @@ public HuffmanScanBuffer(BufferedReadStream stream)
             this.MarkerPosition = 0;
             this.badData = false;
             this.NoData = false;
+            this.eofHitCount = 0;
         }
 
         /// <summary>
@@ -211,13 +215,19 @@ public bool FindNextMarker()
         private int ReadStream()
         {
             int value = this.badData ? 0 : this.stream.ReadByte();
+
             if (value == -1)
             {
-                // We've encountered the end of the file stream which means there's no EOI marker
+                // We've hit the end of the file stream more times than allowed which means there's no EOI marker
                 // in the image or the SOS marker has the wrong dimensions set.
-                this.badData = true;
-                this.NoData = true;
-                value = 0;
+                if (this.eofHitCount > JpegConstants.Huffman.FetchLoop)
+                {
+                    this.badData = true;
+                    this.NoData = true;
+                    value = 0;
+                }
+
+                this.eofHitCount++;
             }
 
             return value;

tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs

@@ -229,6 +229,19 @@ public void Issue2133_DeduceColorSpace<TPixel>(TestImageProvider<TPixel> provide
             }
         }
 
+        // https://github.com/SixLabors/ImageSharp/issues/2638
+        [Theory]
+        [WithFile(TestImages.Jpeg.Issues.Issue2638, PixelTypes.Rgba32)]
+        public void Issue2638_DecodeWorks<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage(JpegDecoder))
+            {
+                image.DebugSave(provider);
+                image.CompareToOriginal(provider);
+            }
+        }
+
         // DEBUG ONLY!
         // The PDF.js output should be saved by "tests\ImageSharp.Tests\Formats\Jpg\pdfjs\jpeg-converter.htm"
         // into "\tests\Images\ActualOutput\JpegDecoderTests\"

tests/ImageSharp.Tests/TestImages.cs

@@ -266,6 +266,7 @@ public static class Issues
                 public const string ExifNullArrayTag = "Jpg/issues/issue-2056-exif-null-array.jpg";
                 public const string ValidExifArgumentNullExceptionOnEncode = "Jpg/issues/Issue2087-exif-null-reference-on-encode.jpg";
                 public const string Issue2133DeduceColorSpace = "Jpg/issues/Issue2133.jpg";
+                public const string Issue2638 = "Jpg/issues/Issue2638.jpg";
 
                 public static class Fuzz
                 {