Override PhotometricInterpretation to RGB only in case of YCbCr, for black and white it should stay as it is

src/ImageSharp/Formats/Tiff/TiffDecoderOptionsParser.cs

@@ -476,15 +476,18 @@ internal static class TiffDecoderOptionsParser
 
             case TiffCompression.OldJpeg:
             {
+                if (!options.OldJpegCompressionStartOfImageMarker.HasValue)
+                {
+                    TiffThrowHelper.ThrowNotSupported("Missing SOI marker offset for tiff with old jpeg compression");
+                }
+
                 options.CompressionType = TiffDecoderCompressionType.OldJpeg;
 
+                if (options.PhotometricInterpretation is TiffPhotometricInterpretation.YCbCr)
+                {
                     // Note: Setting PhotometricInterpretation and color type to RGB here, since the jpeg decoder will handle the conversion of the pixel data.
                     options.PhotometricInterpretation = TiffPhotometricInterpretation.Rgb;
                     options.ColorType = TiffColorType.Rgb;
-
-                if (!options.OldJpegCompressionStartOfImageMarker.HasValue)
-                {
-                    TiffThrowHelper.ThrowNotSupported("Missing SOI marker offset for tiff with old jpeg compression");
                 }
 
                 break;