Fix tests

src/ImageSharp/Formats/Jpeg/Port/Components/ScanDecoder.cs

@@ -621,6 +621,8 @@ namespace ImageSharp.Formats.Jpeg.Port.Components
             short code = -1;
 
             // TODO: Adding this code introduces error into the decoder.
+            // NOTES # During investigation of the libjpeg implementation it appears that they pull 32bits at a time and operate on those bits
+            //         using 3 methods: FillBits, PeekBits, and ReadBits. We should attempt to do the same.
             // It doesn't appear to speed anything up either.
             //  if (this.bitsUnRead < 8)
             //  {

src/ImageSharp/Formats/Jpeg/Port/JpegDecoderCore.cs

@@ -542,11 +542,6 @@ namespace ImageSharp.Formats.Jpeg.Port
                 remaining--;
                 int quantizationTableSpec = this.InputStream.ReadByte();
 
-                if (quantizationTableSpec > 3)
-                {
-                    throw new ImageFormatException($"Bad Tq index value: {quantizationTableSpec}");
-                }
-
                 switch (quantizationTableSpec >> 4)
                 {
                     case 0:
@@ -561,7 +556,7 @@ namespace ImageSharp.Formats.Jpeg.Port
                             this.InputStream.Read(this.temp, 0, 64);
                             remaining -= 64;
 
-                            Span<short> tableSpan = this.quantizationTables.Tables.GetRowSpan(quantizationTableSpec);
+                            Span<short> tableSpan = this.quantizationTables.Tables.GetRowSpan(quantizationTableSpec & 15);
                             for (int j = 0; j < 64; j++)
                             {
                                 tableSpan[QuantizationTables.DctZigZag[j]] = this.temp[j];
@@ -581,7 +576,7 @@ namespace ImageSharp.Formats.Jpeg.Port
                             this.InputStream.Read(this.temp, 0, 128);
                             remaining -= 128;
 
-                            Span<short> tableSpan = this.quantizationTables.Tables.GetRowSpan(quantizationTableSpec);
+                            Span<short> tableSpan = this.quantizationTables.Tables.GetRowSpan(quantizationTableSpec & 15);
                             for (int j = 0; j < 64; j++)
                             {
                                 tableSpan[QuantizationTables.DctZigZag[j]] = (short)((this.temp[2 * j] << 8) | this.temp[(2 * j) + 1]);

tests/ImageSharp.Tests/FileTestBase.cs

@@ -70,7 +70,9 @@ namespace ImageSharp.Tests
             // TestFile.Create(TestImages.Jpeg.Baseline.Ycck), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Baseline.Cmyk), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Baseline.Floorplan), // Perf: Enable for local testing only
+            // TestFile.Create(TestImages.Jpeg.Progressive.Festzug), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Baseline.Bad.MissingEOF), // Perf: Enable for local testing only
+            // TestFile.Create(TestImages.Jpeg.Baseline.Bad.ExifUndefType), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Progressive.Fb), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Progressive.Progress), // Perf: Enable for local testing only
             // TestFile.Create(TestImages.Jpeg.Baseline.GammaDalaiLamaGray), // Perf: Enable for local testing only

tests/ImageSharp.Tests/TestFile.cs

@@ -116,7 +116,7 @@ namespace ImageSharp.Tests
         /// </returns>
         public string GetFileNameWithoutExtension(object value)
         {
-            return this.FileNameWithoutExtension + "-" + value;
+            return $"{this.FileNameWithoutExtension}-{value}";
         }
 
         /// <summary>
@@ -138,7 +138,7 @@ namespace ImageSharp.Tests
         /// </returns>
         public Image<Rgba32> CreateImage(IImageDecoder decoder)
         {
-            return Image.Load(this.image.Configuration, this.Bytes, decoder);
+            return Image.Load(this.GetImage().Configuration, this.Bytes, decoder);
         }
 
         private Image<Rgba32> GetImage()