Add old jpeg compressed tiff test with bi-color

tests/ImageSharp.Tests/Formats/Tiff/TiffDecoderTests.cs

@@ -668,6 +668,7 @@ public class TiffDecoderTests : TiffDecoderBaseTester
     [WithFile(RgbOldJpegCompressed, PixelTypes.Rgba32)]
     [WithFile(RgbOldJpegCompressed2, PixelTypes.Rgba32)]
     [WithFile(RgbOldJpegCompressed3, PixelTypes.Rgba32)]
+    [WithFile(RgbOldJpegCompressedGray, PixelTypes.Rgba32)]
     [WithFile(YCbCrOldJpegCompressed, PixelTypes.Rgba32)]
     public void TiffDecoder_CanDecode_OldJpegCompressed<TPixel>(TestImageProvider<TPixel> provider)
         where TPixel : unmanaged, IPixel<TPixel>

tests/ImageSharp.Tests/TestImages.cs

@@ -799,6 +799,7 @@ public static class TestImages
         public const string RgbOldJpegCompressed = "Tiff/OldJpegCompression.tiff";
         public const string RgbOldJpegCompressed2 = "Tiff/OldJpegCompression2.tiff";
         public const string RgbOldJpegCompressed3 = "Tiff/OldJpegCompression3.tiff";
+        public const string RgbOldJpegCompressedGray = "Tiff/OldJpegCompressionGray.tiff";
         public const string YCbCrOldJpegCompressed = "Tiff/YCbCrOldJpegCompressed.tiff";
         public const string RgbWithStripsJpegCompressed = "Tiff/rgb_jpegcompressed_stripped.tiff";
         public const string RgbJpegCompressedNoJpegTable = "Tiff/rgb_jpegcompressed_nojpegtable.tiff";

tests/Images/Input/Tiff/OldJpegCompressionGray.tiff

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:790662b0fc48d5604e80a9689eb28cfa231be3eadc33f34c9bf43c211cce5c16
+size 440613